Category: ICSE Solutions

ICSE Solutions for Class 6 History and Civics – History – Early Man

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 6 History and Civics Chapter 2 Early Man . You can download the History and Civics ICSE Solutions for Class 6 with Free PDF download option. History and Civics for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Exercise

I. Fill in the blanks:

1. The system of exchanging things is known as Barter.
2. Early man was a Nomad, but later he led a settled life.
3. Instead of killing Animals man domesticated them and used them as means of transport.
4. Man started worshiping Natural forces/gods out of fear.

II. Write True or False against the following statements:

1. The Old Stone Age lasted from 100,000 BC to 8,000
   False.
2. Early Man always lived close to rivers.
   True.
3. The discovery of fire was a pure coincidence.
    True.
4. Fire helped man in making better tools.
   False.
5. Man started making shorter and tinier tools called ‘Microliths’ in the Neolithic Age.
   False.
6. The New Stone Age is known for discovery of agriculture and invention of wheel.
   True.
7. The invention of the wheel made transportation easier and faster.
   True.
8. Primitive men believed in life after death.
   True.

III. Answer the following questions briefly:

Question 1.
When did modern man appear on the earth?
Answer:
The modem man appeared on the earth around 40,000 years ago.

Question 2.
Name the three periods of the prehistoric time.
Answer:
Three periods of prehistory — palaeolithic age, mesolithic age and neolithic age.

Question 3.
How did early man dress himself in the Stone Age?
Answer:
During the Stone Age early man wore animal skins, bark of trees and leaves.

Question 4.
Which discoveries changed the life of Early Man ?
Ans.
The discovery of fire and agriculture changed the life of early man. Later on he started making pottery. Invention of wheel also transformed the life of early man.

Question 5.
How were the tools of the New Stone Age different from those of the Old Stone Age ?
Answer:
During the Old Stone Age stone tools were crude, big and blunt. They were used for different purposes such as cutting trees, killing and skinning animals, chopping meat, etc. During the New Stone Age, tools became smaller, sharper, pointed and fine-shaped. They were used as spears, arrow heads, etc.

Question 6.
Describe the main features of the Neolithic Age ?
Answer:
During the Neolithic Age man least to make better tools grow food crops and domesticate animals. This age remarkable for discovery of agriculture, fine pottery and invention of wheel. Man became a food-producer and began leading a settled life.

Question 7.
How did the invention of wheel change the life of early man?
Answer:
The invention of wheel brought many changes in the life of man. Early man made wheeled-cart which made transportation easier and faster. Potters made fine pottery of various shapes and sizes quickly on wheels. Later the wheel was also used for spinning and weaving cloth of cotton.

Question 8.
Trace the development of early man from being a food gatherer to a food producer.
Answer:
During the Palaeolithic Age, early man was a food gatherer. He wandered from place to place in search of food. He hunted wild animals for their meat which they ate raw. With discovery of fire, he learnt to roast meat. During the Neolithic Age early man began to grow food crops. He became a food-producer. Hence, he settled at one place, began domestication of useful animals and stored grains for future use in pots.

Textbook Keywords

1. Palaeolithic Age:It is the Old Stone Age in which humans made crude stone tools. It extended roughly from 500, 000 BCE to 10, 000 BCE.
2. Mesolithic Age: It is the Middle Stone Age which was a transition period. It extended roughly from 10, 000 BCE to 8,000 BCE.
3. Neolithic Age: It is the New stone Age in which human made well shaped and polished stone tools. It extended roughly from 8,000 BCE to 4,000 BCE.
4. Barter System: It is the system of exchanging services and goods.
5. Chalcolithic Age: It is the Copper-stone Age in which humans made tools of both copper and stone. It extended roughly from 4, 000 BCE to 2, 000 BCE.
6. Bronze: It is the alloy of copper and tin. It is harder and stronger than copper.

Additional Questions

A. Fill in the blanks.

1. 1. In the earliest stages of physical development, humans walked on all four.
2. In earliest times humans lived in caves and other natural shelters.
3. The Old Stone Age humans made stone tools such as hammers, scrapers and axe-heads
4. Early humans did not know how to grow crops. They were hunters and food gatherers
5. To protect themselves from wild animals early humans began to form small groups.
6. Primitive humans painted pictures of animals and hunting scenes on cave walls.
7. The greatest achievement of early humans was the discovery of fire
8. The stone tools of the Neolithic Age were well-shaped and polished.
9. Neolithic humans domesticated dogs, goats, sheep and cattle.
10. The invention of the wheel was a major milestone in the evolution of the civilized human.
11. The system of exchanging services and goods is known as the Barter system.
    
12. Copper and stone tools were used during the Chalcolithic Age.

B. Match the following
                             A                                            B

Answer:

C. Answer the following questions.

Question 1.
Describe the life of prehistoric humans in the earliest times.
Answer:
In earliest times, prehistoric humans lived alone in caves or other natural shelters. They ate wild berries, roots, fruits, insects, worms and flesh of small animals. They used their bare hands to kill small animals. They did not wear any clothes and their bodies were covered with thick hair.

Question 2.
Name the periods into which the Stone Ages can be broadly divided.
Answer:
The Stone Age can be broadly divided into four periods. They are following.

1. Palaeolithic Age or Old Stone Age
2. Mesolithic Age or Middle Stone Age
3. Neolithic Age or New Stone Age
4. Chalcolithic Age or Copper Stone Age

Question 3.
Describe the tools made by humans in the Palaeolithic Age. What purposes did these tools serve?
Answer:
During the Palaeolithic Age mao made crude unpolished tools. They shaped the large stone pieces into, hammers, scrapers and axe-heads. The purposes of these tools were for cutting tree, killing and skinning animals, chopping meat and digging up roots.

Question 4.
What did the people of the Old Stone Age eat?
Answer:
The people of Old Stone Age did not know how to grow crops. Their food consisted of fruits, roots, nuts, eggs of birds and raw flesh of animals and birds.

Question 5.
Where did early humans live? What did they wear?
Answer:
Early humans lived in caves and hide himself among the branches of trees. Early human did not wear clothes, But later they make clothes by stitching animal skins with bone needles.

Question 6.
How do we know that early humans were skillful artists?
Answer:
There is no doubt that early humans were skillful artist because the painted pictures of animals and drawn hunting scenes with great accuracy and skill on cave walls. They also engraved pictures on ivory horns and flat bones.

Question 7.
How did early humans discover fire? How did this discovery help them?
Answer:
Early humans found that when two dry stones rubbed together produce sparks of fire. This discovery bought a great change in their life. They used it for roasting food, lighting his cave, keeping warm in cold season and frightening animals.

Question 8.
What important changes took place in the life style of humans in the New Stone Age?
Answer:
In the New Stone Age human became a food produces from food gatherer. He gave up his cave and made huts of straw and mud and he also made better well grooved and more useful tools.

Question 9.
Discuss two important occupations of humans in the New Stone Age.
Answer:
Agriculture and domestication of animals were two important occupations of humans in the New Stone Age.

Question 10.
How did the invention of the wheel transform the life of the people in the Neolithic Age?
Answer:
The discovery of the wheel was an important achievement of the man in the Neolithic Period.It brought a rapid progress in making beautiful pots. The wheel was used in horse-carts and bullock-carts. Which made transport quite easy and quick. The wheel was used for carrying loads and also used for spinning and weaving. In this way the invention of the wheel was a major achievement of man in his march towards civilization.

Question 11.
Why did early humans make pots? How did the invention of the potter’s wheel affect the art of pottery making?
Answer:
Early humans make pots because they needed pots to store grains, water and food. The invention of the potter’s wheel was boon for potters. They made pots of various shapes and sizes, pots were often decorated with floral designs and geometrical patterns.

Question 12.
‘Agriculture and domestication of animals brought dramatic changes in the of humans’. Explain.
Answer:
Agriculture— The discovery of Agriculture has a great importance in the life of humans. The man now become a food producer instead of a food-gatherer and thus, he began to lead a settled life. He now grow com, vegetables and fruits near his hut.

Domestication— The Domestication of animals help the humans in many ways Dogs, goats, sheep and cattle were domesticated. These animals supplied milk, meat and skins. Bullocks, donkeys and horses were later used to plough the fields. In these ways agriculture and domestication brought dramatic changes in the life of humans.

Question 13.
Write short notes on the following:
1. The barter system
2.Social life during the Neolithic Age
Answer:

1. The barter system It is the system of exchanging services and goods. For example, the potters got food grains in exchange for pots and vice versa.
2. Social life during the Neolithic Age From the earliest times, people had been living in groups. It became necessary to have a code of conduct to regulate and control the activities of the people. These rules became established customs. The oldest, wiser or the strongest man in the village was chosen as the village head man. He maintained law and order in the village and protected the people from enemies.

Question 14.
Mention the chief features of the Chalcolithic Age.
Answer:
Chalcolithic Age is known as the Copper-Stone Age. It was a brief but significant period in the life of man. The main features of the Chalcolithic Age were following.

1. In Chalcolithic Age discovery of metals and improved implements led to the development of agricultural skills to a high degree.
2. Chalcolithic Settlements were rural in nature Society became more complex and was classified into different groups.

D. State whether the following are true or false.

1. The humans of the Old Stone Age were hunters and food gatherers.
   True.
2. Fire was discovered in the Neolithic Age.
   False.
3. The Neolithic humans used digging sticks and stone sickles.
   True.
   
4. Humans did not know spinning and weaving in the New Stone Age.
   False
   
5. Copper is harder and stronger than bronze.
   False.

E. Picture study.

The picture below shows some stone implements.

1. To which prehistoric age do these implements belong?
   Ans. These implements belongs to Neolithic Age.
2. How are these implements different from those belonging to the previous age?
   Ans. These implements were beautiful, well grooved and more useful than belonging to the previous age.
3. What purpose did these tools serve?
   Ans. Humans used these tools to till the soil and to reap the crops.
4. Mention five important changes that took place in the lifestyle of humans of this period.
   Ans.
   1. In Neolithic age man became a food producer from food gatherer.
   2.Man gave up his cave and made huts of straw and mud near his fields.
   3.Man made better, beautiful well grooved, and more useful tools.
   4. The invention of wheel made the life easier and more comfortable.
   5. Man began to live in groups and human life became more organized.

Selina Concise Physics Class 6 ICSE Solutions – Simple Machines

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Physics. You can download the Selina Concise Physics ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Physics for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Physics Chapter 4 Simple Machines

• Synposis
• Work is said to be done when a force applied on a body moves it. If the body does not move on applying a force on it, no work is done by the force.
• The capacity of doing work is called energy.
• A machine is a device which helps us to do work more easily.
• A machine enables us to apply a less effort for a load greater than the effort or to apply the effort at convenient point and in a desired direction.
• Some machines are simple and some are complex.
• The mechanical advantage of a machine is the ratio of the load to the effort, i.e., Mechanical advantage = Load / Effort
• Smaller the effort required for a certain load, greater is the mechanical advantage of the machine.
• The efficiency of a machine is the ratio of the useful work done on the load by the machine to the work put into the machine by the effort, i.e.
  Efficiency = Work output / Work input
• The efficiency of an ideal machine is 1 (or 100 per cent).
• The efficiency of an actual machine is less than 1 because some part of the work put into the machine is lost in overcoming the friction between the moving parts of the machine.
• A lever is a simple machine which we most commonly use in our daily life. It is a rod which can turn about a fixed point called the fulcrum.
• The mechanical advantage of a lever is equal to the ratio of the effort arm to the load arm, i.e. Mechanical advantage of a lever = Effort arm / Load arm
  The levers are of three kinds :
  Class I levers which have fulcrum in between the load and the effort.
  Class II levers which have load in between fulcrum and the effort.
  Class III levers which have effort in between the fulcrum and the load.
• The mechanical advantage of class I lever can be 1, more than 1 or less than 1.
• The mechanical advantage of class II levers is always more than 1.
• The mechanical advantage of class III levers is always less than 1.
• A pulley is a simple machine which is used for raising a load up by applying the effort downwards.
• The mechanical advantage of an ideal pulley is 1. In an actual pulley, due to friction, the mechanical advantage is less than 1 (i.e., the effort is more than the load).
• The pulley allow us to apply the effort downwards which is a convenient direction.
• The wheel and axle is a simple machine having a wheel and an axle. The linear motion of axle is obtained by rotating the wheel so as to reduce friction. Example: Steering wheel, screw drivers, water tap etc.
• An inclined plane is a simple machine which is used to move a load up with a less effort. It is a sloping (or slanting) surface.
• Less the slope of the inclined plane, less is the effort needed to push a load up.
• The mechanical advantage of an inclined plane is greater than 1 (i. e. a less effort is required to push a heavy load up an inclined plane).
• A wedge is a sharp edge formed by joining the two inclined planes together. Example: nail, knife, axe, plough etc.
• A screw is a modified form of an inclined plane.
• A screwjack is a simple machine having a combination of a screw and a lever. It is used to lift the heavy vehicles such as cars, trucks, buses etc.
• Machines are used for our convenience. Therefore, we should take proper care of a machine by painting the machine parts to avoid rusting, lubricating its parts to reduce friction etc. This increases the life span of the machine.

Test yourself

A. Objective Questions

1. State whether the following statements are True or False.

(a) A boy does work while pushing a wall.
Answer. False

(b) A machine performs work by itself.
Answer. False

(c) In an ideal machine, work done on load is equal to the work done by effort.
Answer. True

(d) All levers are force multipliers.
Answer. False

(e) A pulley changes the direction of force.
Answer. True

(f) An inclined plane always has the mechanical advantage more than 1.
Answer. True

2. Fill in the blanks

(a) The useful work done by an actual machine is always less than the work done on the machine.
(b) In class II levers, the load is in between fulcrum and effort.
(c) The mechanical advantage of class III lever is always less than 1.
(d) A pulley is used to change the direction of effort.
(e) Mechanical advantage of an inclined plane is always greater than 1.

3. Match the following

Answer.

4. Select the correct alternatives

(a) For an ideal machine, the efficiency is

1. greater than unity
2. less than unity
3. equal to unity
4. depends on the value of load

(b) Mechanical advantage of a machine is defined as:

1. Load X Effort
2. Load / Effort
3. Load + Effort
4. Effort / Load

(c) The mechanical advantage of a lever is equal to:

1. Load arm / Effort arm
2. Effort arm / Load arm
3. Load arm + Effort arm
4. Load arn — Effort arm

(d) A pulley is used because it

1. has the mechanical advantage greater than one
2. has 100% efficiency
3. helps to apply the force in a convenient direction
4. requires more effort to raise a less load.

(e) Wheel is used with axle because

1. sliding friction is less than the rolling friction
2. rolling friction is less than the sliding friction
3. they work as the inclined plane
4. They help us to change the direction of force.

B. Short/Long Answer Questions

Question 1.
When is work said to be done by a force ?
Answer:
Work is said to be done when a force moves an obj ect through a distance in its own direction.

Question 2.
What is energy ?
Answer:
Energy: The ability or capacity to do work is called energy.

Question 3.
What do you understand by a machine ?
Answer:
Machine: A machine is a device that allows us to do work with less effort. Machines make our work easier to do. Machines have made our li ves comfortable and faster.

Question 4.
What is the principle on which a machine works ?
Answer:
Principle of a Machine: The work output of a machine is equal to the work input.

Question 5.
State two functions of a machine.
Answer:
Various functions that a machine can perform are:

1. Changing the direction of applied force — Example: When a flag is hoisted with the help of a pulley.
2. Changing the magnitude of applied force — Example: Bottle opener multiplies the applied force and much less effort is required to open the cap.
3. Applying force at a convenient point — Example: In a pair of scissors, the input force is applied at the handle of the scissors which cuts the paper at the other end of the blade.
4. Changing the speed of an object — Example: While riding a bicycle, force is applied on pedals which multiplies the speed.

Question 6.
Name six simple machines. Give an example of each machine.
Answer:
The Simple Machines and there examples are as follows:

1. The lever: Examples are a crow bar, claw hammer, a pair of pilers etc.
2. The Inclined plane: Examples are ramp, staircase, hilly roads etc.
3. The wedge: Examples are knife, axe, plough, nail etc.
4. Screw: Examples are A screw.
5. The wheel and axle: Examples are steering wheel of a car, bicycle pedal etc.
6. The pulley: Examples are a pulley used in raising a load.

Question 7.
Define the term ‘work input’ and ‘work output’ in relation to a machine.
Answer:
Work input is work done on a machine equal to the effort force times the distance through which the force is applied.
Work output is work that is done by a machine equals resistance force times the distance through which the force applied.
For an ideal machine, the work output is equal to the work input i. e. the efficiency.

Question 8.
Explain the term mechanical advantage of a machine.
Answer:
The mechanical advantage of a machine is the ratio of the load to the effort. In other words

Question 9.
Define the term efficiency of a machine.
Answer:
The ratio of the work done by the machine to the work done on the machine is called efficiency of a machine

(Work done by a machine is called the output energy and the work done on a machine is called the input energy.)

Question 10.
What is an ideal machine ?
Answer:
A machine is which no part of the work done on the machine is wasted, is called an ideal or perfect machine. Thus, for an ideal machine, the work output is equal to the work input, i.e., the efficiency of an ideal machine is 1 (or 100 per cent).

Question 11.
Can a machine have an efficiency of 100% ? Give a reason to support your answer.
Answer:
Efficiency of a machine is always less than 100% as output energy is always less than the input energy, because some energy is lost to overcome friction.

Question 12.
A machine is 75% efficient’. What do you understand by this statement ?
Answer:
If a machine is 75% efficient, it means that 75% of the work input to the machine is obtained as the useful work output. The remaining 25% of the work input has been lost in overcoming the friction.

Question 13.
What is a lever ?
Answer:
Lever: A lever is a simple rigid bar which is free to move around a point called fulcrum.

Question 14.
Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.
Answer:
The levers are of three kinds :
Class I levers which have fulcrum in between the load and the effort.

Class II levers which have load in between the fulcrum and the effort.

Class III levers which has effort in between the fulcrum and the Load

Question 15.
What do you mean by the mechanical advantage of a lever ?
Answer:
The mechanical advantage of a lever is equal to the ratio of the effort arm to the load arm. This is also called the principle of a lever.

Question 16.
Which class of lever has the mechanical advantage always more than 1 ? Give an example.
Answer:
The mechanical advantage of class II levers is always more- than 1.
Example – Nut cracker, wheel barrow, bottle opener etc.

Question 17.
Which class of lever has the mechanical advantage always less than 1 ? Give an example.
Answer:
The mechanical advantage of class III levers is always less than 1.
Example: a pair of tongs, sugar tongs, knife, forceps etc.

Question 18.
Give one example of class I lever in each case where the mechanical advantage is

1. more than 1
2. equal to 1
3. less than 1.

Answer:

1. more than 1: Load arm of pliers
2. equal to 1: See – saw
3. less than 1: The load arm of a pair of scissors.

Question 19.
Name the class to which the following levers belong:

Answer:
(a) A pair of scissors — Class I lever
(b) a lemon squeezer — Class II lever
(c) a nut cracker — Class II lever
(d) a pair of sugar tongs — Class III lever
(e) a beam balance — Class I lever
(f) an oar rowing a boat — Class I lever
(g) a wheel barrow — Class II lever
(h) a see saw — Class I lever
(i) a pair of pilers — Class I lever
(j) a crow bar — Class I lever

Question 20.
The diagram given below shows the three kinds of levers. Name the class of each lever and give one example of each class.

Answer:

Examples : The examples of class I levers are : a see saw, a pair of scissors, a pair of pilers, crow bar, common balance, spoon opening the lid of a tin can, handle of a hand pump.

Examples : The examples of lever of class II are : nut cracker, wheel barrow, paper cutter, mango, lemon squeezer, bottle opener.

Examples: The examples of levers of class III are : a pair of tongs, sugar tongs, knife, forceps,-forearm of a person holding a load, spade for lifting soil or coal.

Question 21.
Draw diagrams to illustrate the positions of fulcrum, load and effort, in each of the following:
(a) a see saw
(b) a beam balance
(c) a nut cracker
(d) a pair of forceps
Answer:

Question 22.
How can you increase the mechanical advantage of a lever ?
Answer:
The mechanical advantage of a lever can be increased by increasing the effort arm or reducing the load arm.

Question 23.
How does the friction at the fulcrum affect the mechanical advantage of the lever ?
Answer:
Friction at the fulcrum reduces the mechanical advantage.

Question 24.
State three differences between the three classes of levers.
Answer:

Question 25.
What is a pulley ?
Answer:
Pulley: It is a flat circular disc with a groove in its edge and a rope passing through the groove. It is capable of rotating around a fixed point passing through its central axis called axle.

Question 26.
What is the mechanical advantage of an ideal pulley ?
Answer:
In an ideal pulley, the effort applied is equal to the load to be lifted.
i.e. Effort = Load
Mechanical advantage = Load / Effort = 1

Question 27.
The mechanical advantage of an actual pulley is less than 1. Give a reason. What is the justification for using the pulley then ?
Answer:
In an actual pulley due to friction, the mechanical advantage is less than 1 (i.e. the effort is more than the load).
The reason for using the pulley when its mechanical advantage is equal to 1 or less than 1 is that the pulley allows us to apply the effort downwards i.e. in a convenient direction. To raise a load directly upwards is difficult. But with the help of a pulley, the effort can be applied in the downward direction to move the load upwards. One can hang on it to make use of his own weight also in order to apply the effort.

Question 28.
Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
Answer:
To raise a load, the load is attached to one end of the string and the effort is applied at the other end by pulling it is downward direction . as shown in fig.

Question 29.
What is an inclined plane? What is its use ? Give two examples where ¡t is used.
Answer:
An inclined plane is a rigid sloping surface over which heavy loads can be raised or lowered to a certain height or depth.
The mechanical advantage of an inclined plane is the ratio of the length of the plank to the vertical height of the load raised. Its value is greater than one. Therefore, an inclined plane acts as a force multiplier. Thus, it can be used to lift heavy loads.
Example : If a heavy box needs to be loaded on a lorry, it is far easier to push it over an inclined plane than to lift it up. Steeper the inclined plane, greater will be the effort required to push up the load.
Sloping ramps, flyovers, roads on hills and staircases are all examples of inclined planes.

Question 30.
What is a screw ? Give two examples.
Answer:
A screw is a simple machine which appears like an inclined plane wound around a rod with a pointed tip.
Examples : ajar lid, a drill.

Question 31.
What is wheel and axle ? Give two examples.
Answer:
The wheel and axle is a simple machine having a wheel and an axle. The linear motion of axle is obtained by rotating the wheel so as to reduce friction. Example: Steering wheel, screw drivers, water tap etc.

Question 32.
How does a wheel help in moving the axle ?
Answer:
Wheel-and-axle arrangement consists of two cylinders of different diameters joined together such that if one is made to rotate, the other also rotates. The axle is a cylindrical rod fixed to the centre of a circular disc-like object called the wheel.

This machine acts as a speed multiplier device.
In riding a bicycle, when we apply force on the wheel (by pedal), the fixed axle rotates with it easily. This force that turns the axle produces a much larger movement of the wheel.

Question 33.
What is a wedge ? Give two examples.
Answer:
A wedge is a double inclined plane such that the two sloping surfaces taper to form either a sharp edge or a pointed edge. Examples : A knife, an axe, a chisel.
In some special cases, the number of inclined planes used can be more than two as well. In such cases, the sloping surfaces generally taper to form either a very sharp or a pointed edge to split or pierce materials. Pins, nails and needles are examples of pointed wedges. The front end of a boat is shaped like a wedge so that it can easily cut across the flowing water.
The wedge works on a principle of an inclined plane.

Question 34.
Name the machine to which the following belong :

1. Beam balance
2. Lemon crusher
3. Sugar tongs
4. Ramp
5. Door knob
6. Needle

Answer:

1. Beam balance — A lever (lever of class I)
2. Lemon crusher — A lever (lever of class II)
3. Sugar tongs — A lever (lever of class III)
4. Ramp — An inclined plane
5. Door knob — Wheel and axle
6. Needle — Wedge

Question 35.
What care would you take to increase the life span of a machine which you use ?
Answer:
Taking care of machines: Some of the ways in which machines should be cared for are given below :

1. Machines should be kept in a clean environment, which is free from dust and moisture.
2. When not in use, machines should be kept covered to prevent collection of dust on them.
3. Machines made of iron should be protected from rust by coating them with paint.
4. The moving parts of a machine should be regularly oiled with a good-quality machine oil to reduce friction and wear and tear. The above care of machines increases their life.

Question 36.
Select the correct statement :
(a) A wheel barrow is a lever of class I.
(b) The efficiency of a machine is always 100%
(c) Friction in moving parts of a machine reduces its efficiency.
(d) No lever has the mechanical advantage greater than 1.
(e) It is easier to lift a load vertically up than to push it along an inclined plane.
(f) A screw is made by two inclined planes placed together.
Answer:
(c) Friction in moving parts of a machine reduces its efficiency.

C. Numericals

Question 1.
In a machine an effort of 10 kgf is applied to lift a load of 100 kgf. What is its mechanical advantage ?
Answer:
Given,
Load = loo kgf
Effort = 10 kgf

Question 2.
The mechanical advantage of a machine is 5. How much load it can exert for the effort of 2 kgf ?
Answer:
Given,
Mechanical advantage = 5
Effort 2 kgf

Question 3.
The mechanical advantage of a machine is 2. It is used to raise a load of 15 kgf. What effort is needed ?
Answer:
Given,
Mechanical advantage = 2
Load = 15 Kgf

Question 4.
A lever of length 100 cm has effort of 15 kgf at a distance of 40 cm from the fulcrum at one end. What load can be applied at its other end ?
Answer:

Question 5.
In a lever, fulcrum is at one end at a distance of 30 cm from the load and effort is at the other end at a distance of 90 cm from the load. Find :
(a) the length of load arm,
(b) the length of effort arm, and
(c) the mechanical advantage of the lever.
Answer:

Selina Concise Biology Class 6 ICSE Solutions – The Flower

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Biology. You can download the Selina Concise Biology ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Biology for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Biology Chapter 2 The Flower

Review Questions

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) In a germinating seed, the roots develop from:
(i) Radicle
(ii) Plumule
(iii) Tegmen
(iv) Hilum

(b) In a germinating seed, the shoot develops from:
(i) Radicle
(ii) Plumule
(iii) Tegmen
(iv) Hilum

(c) Which one of the following is a monocotyledonous seed ?
(i) Bean
(ii) Pea
(iii) Maize
(iv) Gram

(d) If the cotyledons are pushed above the soil, then such type of germination is called :
(i) Epigeal
(ii) Hypogeal
(iii) Perigeal
(iv) Progeal

(e) If the cotyledons remain under the soil, then such seeds type of germination is called:
(i) Epigeal
(ii) Hypogeal
(iii) Perigeal
(iv) Progeal

(f) Pollen is produced in the:
(i) Filament
(ii) Style
(iii) Pistil
(iv) Anther

(g) Reproductive whorls of a flower are:
(i) Stamens and carpels
(ii) Sepals and petals
(iii) Sepals and stamens
(iv) Petals and carpels

PQ. Vegetative propagation is not observed in:
(i) Potato
(ii) Tomato
(iii) Pea
(iv) Bean

(h) Which one of the following is a false fruit ?
(i) Tomato
(ii) Apple
(iii) Potato
(iv) Pea

(i) In a seed, food is generally stored in:
(i) Radicle
(ii) Plumule
(iii) Fruit
(iv) Catyledons or endosperms

1. Given below is a longitudinal section of a bean seed. Label the parts marked 1 to 5 and write their functions.

Answer :
1. Testa (seed coat)
2. Plumule
3. Radicle
4. Micropyle
5. Cotyledon

1. Testa (seed coat) — It protects the seed from insects and bacteria as well as from mechanical injury.
2. Plumule — Plumule develops into a shoot.
3. Radicle — Radicle develops into a root
4. Micropyle — The micropyle absorbs as much water as is required for germination.
5. Cotyledon — Contain stored food material which is used by the seeding during germination.

2. Name the following:

(a) A seed which shows hypogeal germination.
Ans. pea seed, maize. seed
(b) Amonocotseed.
Ans. Maize seed, wheat seed
(c) A dicot seed.
Ans. Bean seed, gram seed, pea seed
(d) A seed which shows epigeal germination.
Ans. Bean seed castor seed, tamarind seed

Question 3.
Differentiate between the following pairs of terms:
Answer :
(a) Radicle and plumule.
Radicle: In a seed the radicle lies downwards near the lower pointed end of the grain. It gives rise to the root.
Plumule: In a seed the plumule lies upwani near the cotyledon and gives rise to the shoot.

(b) Ilium and micropyle.
Answer :
IlIum : On one side of seed câat, there is scar called hi hum, which marks the place where the seed was attached to the fiiüt wall.
Micropyle : Above the hilum is a small pore called micrope. The micropyle absorbs as much water as is required for germination

(c) Testa and tegmen.
Answer :
Testa: The seed is protected by a thick outermost coat called the testa or seed coat.
Tegmen: Under the testa lies a very thin membrane called the tegmen.

Question 4.
Give two functions of a fruit.
Answer :
Functions of a fruit are:

1. Fruit is a protective case for the seeds.
2. Fruit is a temptation to animals and man to eat it and scatter the seeds

Question 5.
Match the columns :
Column A           Column B

Answer :

Question 6.
Radicle emerges out of the seed earlier than plumule.What one advantage is served by this ?
Answer :
Radicle comes out of the seed earlier than the plumule has advantages as it gets water and minerals from the soil and gives it to the growing plumule.

Question 7.
State whether the following statements are True or False.

(a) Some seeds have no cotyledons.
False
(b) Warmth is necessary for the germination of seeds.
True
(c) All seeds have two cotyledons.
False
(d) Oxygen is necessary for the germination of seeds.
True

Question 8.
State one function of the following:
(a) radicle
(b) cotyledons
(c) endosperm
(d) micropyle
Answer :

1. Radicle — form the roots
2. Cotyledons — On removing th& testa and the tegmen from a soaked bean seed, you will find that the seed is made up of two fleshy seed leaves called the cotyledolm. They contain stored food material which is used by the seedlling for growth.
3. Endosperm—ovary forms the fruit.
4. Micropyle —Above the hilum is a small pore called micropyle (micro = small, pyle = passage). The micropyle absorbs and allows as much water as is required for germination.

Question 9.
The three conditions necessary for germination of seeds are (tick the correct answer):
(a) Oxygen, suitable temperature and water.
(b) Good soil, water and air
(c) Good soil, suitable temperature and light.
(d) Light, oxygen, and temperature.
(e) Oxygen, carbon dioxide, and light.

Question 10.
Name the part of the seeds from which the following are given out:
(a) Roots : .
(b) Leaves :
Answer :
(a) Roots — Radicle give rise to roots.
(b) Leaves—Plumule gives rise to shoot bearing leaves.

Question 11.
In the spaces provided below, draw labelled diagrams to show the three stages in the germination of any seed you have observed.
Answer :

Long Answer Questions
(Write the answers in your note-book)

Question 1.
What is meant by pollination ? Name the two types of pollination.
Answer :
The transfer of the pollen grains from the anthers to the stigma of a flower is called pollination.
The two types of pollination found in flowering plants are.

1. self-pollination – that occurs within the same plant.
2. cross-pollination – that occurs between two flowers of two different plants but of the same kind.

Question 2.
Imagine that all the seeds produced by a plant happen to fall under the same plant and sprout into new plants. Mention any two problems that will be faced by the new plants.
Answer :
If all the seeds produced by a plant happen to fall under the same plant and sprout into new plants then in this situation plants will face the following problems:

1. A large number of plants will grow in a small limited space. The water and the minerals available to them in the soil will be limited.
2. The air surrounding them will not be enough and less sunshine will be available to them. As a result, most of these sprouted plants will die.

Question 3.
What is a flower ? Draw a typical flower and label its different parts.
Answer :

A flower is a reproductive part of a plant. It helps in sexual reproduction as it has male parts and female parts.
A fully opened flower has the following parts:
Stalk—A flower is attached to the shoot by means of stalk or pedicel stalk. The tip of the stalk is swollen or flattened. This is called toms or thalamus or receptacle.
The different parts of a flower are inserted on the thalamus. There are usually four whorls as Calyx

• (Sepals)
• Corolla (Petals)
• Androecium (stamens)
• Gynoecium (Carpels)
• Present on the thalamus.

1. Sepals (Calyx): These are the outermost part of the flower. These are leaf like and green in colour. This is the outer covering of the flower and form outer whorl in a flower. The Calyx (sepals) enclose the inner parts of the flower when it is a bud. It is protective in function.
2. Corolla (Petals): Petals form the second whorl inner to the sepals. These are usually coloured, gaudy, or white in colour and scented and give sweet smell. The value of a flower is due to the attractive colour of the petals. These attract the insects for pollination.
3. Stamens (Androecium): The third whorls inner to the petals are stamens. This third whorl is called Androecium. These are the male parts of the flower. Each stamen is formed of a long narrow, hair like structure called filament. On its tip it bears a rounded broad sac like structure called anther. Each anther has two anther lobes. Each anther lobe has two pollen sacs which have powdery mass called pollen grains.
4. Carpels (Gynoecium): Carpels are the inner most or fourth whorl in a flower. It is lodged on the thalamus and forms the female part of a flower. This whorl of carpels is called gynoecium. Each carpel or pistil has three parts,
   1. The lower most, swollen part is ovary. It is attached to the thalamus
   2. The middle part is style which is narrow, thread like
   3. Stigma: The style ends in a knob like, rounded structure which is sticky in nature to receive the pollen grains.The ovaries contain ovules which later turn into seeds after fertilization and the ovary wall forms the fruit sometimes the thalamus also becomes a part of the fruit as in apple.

Question 4.
With the help of a suitable labelled diagram, describe the structure of a dicot seed.
Answer :

It is a dicotyledonous and non-endospermic seed. It is produced in a long cylindrical pod (fruit – phali) External characters. The seed is brown or whitish brown in colour. The seed is hard and smooth and kidney shaped i.e.Convex on one side and concave on the other side. Concave side bears whitish scar called hilum. It is the place which is attached to the wall of the pod through a stalk called funicle. At one side of the hilum is a small pore called micropyle water enters through it.

Internal structure — The seed is covered by a hard, tough covering called testa. Inner to the tests is the embryo. Embryo consists of two cotyledons and embryo axis. Embryo axis has plumule and radicle. The plumule is present in between the two cotyledons and its top bears two folded tiny leaves. It forms future shoot and leaves of the growing seed. Radicle is rod shaped and is out of the two cotyledons. It forms the root of the growing seed. When the seed grows the two cotyledons come out of the soil and form cotyledonary leaves and turn green in colour. Cotyledons give food to the growing seedling as it has food. The germination in this seed is epigeal as cotyledons come outside the soil in the growing seed.

Question 5.
Define germination ? Name the two types of germination. Explain with examples.
Answer :
The growth and development of the embryo present in the seed into a seedling (or a young plant capable of independent existence) is called as seed germination.
The embryo in a seed remains inactive or dormant. When the seed is put into the soil and given water and under suitable temperature, the embryo becomes active on absorbing the water and the embryo turns into a seedling.

Types of germination — There are three types of germinations.
(i) Epigeal
(ii)Hypogeal
(iii) Viviparous
(i) Epigeal germination — Epi means above ; geo-ground (earth)
When the cotyledons in growing seed come out of the soil it is epigeal type of germination as in case of castor seed, cucumber, tamarind, bean seed the cotyledons come out of the soil and turn green. These are called cotyledonary leaves. These cany on photosynthesis till new leaves arise.

(ii) Hypogeal germination—Hypo-below, gea soil.
When in a growing seed the cotyledons remain under the ground as in case of gram, pea, groundnut and maize. The plumule firms the aerial shoot to which bears leaves and the radicle gives rise to roots. The growing seedling gets food from the cotyledons. As the seedling grows the cotyledons die in the soil.

(iii) Viviparous germination—This is special type of germination.
This occurs in plants growing along the sea coasts and in salt lakes. The seed start growing while it is still attached to the plant as in mangrove plants. The embryo comes out of the fruit with a long, dart like radicle. It falls directly into soft, slushy, wet mud. The radicle gives root and establishes as a seedling and the plumule give rise to shoot. This is in mangrove plants.

Question 6.
What are the three conditions necessary for the germination of seeds. How would you demonstrate this?
Answer: 
F or successful germination of any viable seed, three external conditions are necessary as:

1. Water or moisture
2. Warmth or temperature
3. Air or oxygen.

We can demonstrate this with “Three seed experiment This is a simple experiment to demonstrate the necessity of these factors for proper germination.

Experiment:
Three seed experiment to demonstrate germination Three mature dried bean seeds are taken and tied on a wooden strip at three different positions (above the figure). This strip is placed in a beaker containing water in such a way that the lower seed is completely submerged in water, the middle seed is partially submerged inside the water and the top seed is kept above water. This set-up is left in a warm place for few days.

It is observed that the middle seed shows germination and gives out radicle and shoot leaves. The top seed shows no growth and the bottom one shows negligible growth. The middle seed gets fully germinated due to the fact that this seed has all the favourable conditions required for germination i.e., air (oxygen), moisture and warmth (favourable temperature), which are necessary for germination.

Question 7.
Give the main difference between hypogeal and epigeal and germination.
Answer :
Epigeal germination—Epi means above; geo-means ground (soil). When the cotyledons in a growing seed come out of the soil it is epigeal type of germination as in case of castor seed, bean seeds, pulses, tamarind cucumber.
The cotyledons come out of the soil and turn green these are cotyledonary leaves and carry on the function of photosynthesis till new leaves arise in the growing seedling. Hypogeal germination — Hypo-below, geo-soil it is that type of germination in which in the growing seed the cotyledons remain under the soil as in case of pea, gram, ground-nut, maize. The plumule forms the aerial shoot which later bears leaves and die radicle gives rise to root. The tiny seedling gets food from the cotyledons till it establishes itself in the soil by its roots and starts getting water and minerals and as well the new leaves arise on the ascending axis and they start making food by the process of food making.

Differences—

Epigeal germination

1. In this type of germination the cotyledons come out of the soil.
2. The cotyledons turn green as they come out of the soil and serve as cotyledonary cotyledons
   leaves and carry on photo¬synthesis to make food for the growing seedling.
3. The cotyledons become pale and fall off when the ascending axis bear leaves

Hypogeal germination

1. In this type of germination the cotyledons remain under the soil.
2. The cotyledons remain under the ground and the seedling gets food from the till it establishes in the soil.
3. The cotyledons get rotten up in the soil when the seedling matures.

Question 8.
State the location of the following in a flower:
Answer :

1. Sepals: These are the outermost part of the flower. These are leaf like and green in colour. This is the outer covering of the flower and form outer whorl in a flower. The Calyx (sepals) enclose the inner parts of the flower when it is a bud. It is protective in function.
2. Petals: Petals form the second whorl inner to the sepals. These are usually coloured, gaudy, or white in colour and scented and give sweet smell. The value of a flower is due to the attractive colour of the petals. These attract the insects for pollination.
3. Anther—It is present at the end of a stamen. Anther has poller sacs in which pollen grains are formed. Pollen grains contain the male gametes.
4. Stigma—It is the terminal knob-like part, it may be divided into two or more lobes and assume a feathery appearance. The stigma is covered with hair or with glandular papillae. It serves as the landing place grains for pollen during pollination.

Question 9.
Given below is the diagram of a typical flower. Label the parts marked by guidelines.

Answer:

 

Question 10.
Give the difference in the function between the following parts:
(a) Ovary and ovule
(b) Petal and sepal
(c) Filament and style
(d) Pollen and ovule
Answer :
(a) Ovary and ovule —

1. Ovary is the female reproductive part of a flower and ovules are located inside the ovary.
2. Ovary after fertilization turns into a fruit whereas ovules turn into seeds of fruit.

(b) petal and sepal—Petals are colourful and attractive and helps to attract insects for pollination whereas the main function of sepals is to provide protection to the growing bud.

(c) filament and style—The filament is a stalk like structure that attaches and support the flower and support the anther which is the structure that produces pollens whereas the style transfers the male gametes of the pollen grains into the ovary.

(d) pollen and ovule — The function of pollen is to deliver male gametes (sperm) from stamen of a plant to an ovule whereas ovule, when fertilized, well developed into a seed. It is a female reproductive cell.

Selina Concise Physics Class 6 ICSE Solutions – Light

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Physics. You can download the Selina Concise Physics ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Physics for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 6 Physics ICSE SolutionsChemistryBiologyMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 6 Physics Chapter 5 Light

• Synposis
• Light itself is not visible, but in the presence of light other objects become visible A.
• Light is defined as the external physical cause that affects the eye to produce the sensation of vision.
• Two types of sources of light are:
  (1) Natural sources such as sun, stars andjugnu.
  (2) Artificial sources such as fire, electric lamp, electric tube light, a burning candle, a kerosene lamps heated bodies, etc.
• The bodies which themselves emit light are called luminous bodies. Examples: torch, electric lamps electric tube light, burning candle, kerosene lamp, sun, stars. Jugnu etc.
• The bodies which do not emit light by their own, but they become visible because of the light falling on them from a luminous body, are called non-luminous bodies. Examples: moon, earth, table, book, chair etc.
• A medium which allows the passage of light through it easily, is called a transparent medium. Examples: glass, air, water etc.
• A medium which allows only a small amount oflight to pass through it, is called a translucent medium. Examples: ground glass, tracing paper etc.
• A medium which does not allow anydight to pass tough it, is called an opaque medium. Examples: wood, metals etc.
• Light travels in a straight line path. This is called the rectilinear propagation oflight.
• The pin hole camera is a simple application of the rectilinear propa – gation oflight.
• The image (or picture) formed in a pin hole camera is upside down (i.e. inverted). On increasing the distance of screen from the pin hole, the size of image increases.
• The shadow of an opaque object is the dark patch obtained on the screen when that opaque object is placed in the path of light.
• Shadow is formed because light travels in a straight line path.
• The shadow is similar to the shape of the object.
• The part of the shadow where no light reaches from the source is completely dark and is called the umbra.
• The part of the shadow where light reaches from only a portion of the source is partially dark and is called the penumbra.
• There is only umbra in the shadow of an opaque object due to a point source. The umbra is bigger in size than that of the obj ect. The umbra increases in size if the screen is moved away from the object.
• The shadow of an object due to a light source smaller than the object contains an umbra surrounded by a penumbra. The umbra is bigger in size than that of the object. Both the umbra and penum¬bra increase in size as the screen is moved away from the source.
• The shadow of an opaque object due to a light source bigger than the object contains an umbra (which is much smaller in size than the object) surrounded by a penumbra. The umbra diminishes while the penumbra increases in size if the screen is moved away from the object.
• Lunar and solar eclipses are the examples of formation of shadows in nature.
• A lunar eclipse is caused on a certain full moon night when the earth comes in between the sun and the moon so that the earth casts its shadow on the moon.
• A solar eclipse is caused on a certain new moon’s day when the moon comes in between the sun and the earth so that the moon casts its shadow

Test yourself

A. Short Answer Questions

1. Write true or false for each statement

(a) The moon is a natural source of light.
Answer. False

(b) The moon is self luminous.
Answer. False

(c) We can see an object through an opaque medium.
Answer. False

(d) Light passes through glass.
Answer. True

(e) Light travels in a straight line path. .
Answer. True

(f) Image formed in a pin hole camera is real.
Answer. True

(g) The image in a pin hole camera gets blurred if the hole is made bigger.
Answer. True

(h) A shadow is formed because light travels in a straight line path.
Answer. True

(i) Solar eclipse occurs when the sun comes in between the earth and the moon.
Answer. False

(j) If the shadow of earth falls on the moon, the eclipse is called the lunar eclipse.
Answer. True

2. Fill in the blanks

(a) Light gives us the sensation of vision.
(b) The sun is a natural source of light.
(c) A medium through which light cannot pass is called the opaque medium.
(d) A medium which allows light to pass through it easily is called the transparent medium.
(e) Moon is a non-luminous body.
(f) Light travels in a straight line path.
(g) In a pin hole camera, the image formed is inverted and real.
(h) The darkest portion of a shadow is called the umbra.
(i) The less dark portion of a shadow is called the penumbra.
(j) Lunar eclipse occurs when the earth comes in between the moon and the sun.

3. Match the following columns

4. Select the correct alternative

(i) The natural source of light is

1. candle flame
2. electric lamp
3. sun
4. kerosene lamp

(ii) The formation of inverted image in a pin hole camera shows that

1. light enables us to see
2. light travels in a straight line path
3. light can pass through the pin hole
4. light does not pass through the pin hole

(iii) The luminous body is

1. a lighted bulb
2. earth
3. noon
4. table

(iv) Umbra is a region of

1. complete darkness
2. partial darkness
3. complete brightness
4. partial brightness

(v) Penumbra is a region of

1. complete darkness
2. complete brightness
3. partial brightness
4. none of the above

(vi) Solar eclipse occurs on

1. every new moon’s day
2. certain new moon’s day
3. every full moon’s day
4. certain full moon’s day

(vii) Lunar eclipse occurs on

1. every full moon’s night
2. certain full moon’s night
3. every new moon’s day
4. certain new moon’s day

B. Short/Long Answer Questions

Question 1.
What is light ? Define it.
Answer:
Light is a form of Energy i. e. The external physical cause that affects our eye to produce the sensation of vision.

Question 2.
How does light make an object visible ?
Answer:
An object becomes visible to us when the light after striking the object reaches our eyes. Light itself is not visible, but light makes objects visible to us.

Question 3.
Name two natural sources of light.
Answer:
Sun, stars,jugnu, firefly.

Question 4.
List two artificial sources of light.
Answer:
Electric bulb, torch, an oil lamp, fluorescent tube, candle.

Question 5.
Differentiate between the luminous and non-luminous bodies. Give two examples of each.
Answer:
Difference Between
Luminous
The bodies which have light of their own e.g. sun stars, bulb, candle, oil lamp, torch, a lantern.
Non-Luminous
The bodies-which do not have their own Iight.e.g. moon, chair, table. When light falls on them, they become visible.

Question 6.
Is the moon a luminous object ?
Answer:
Moon is not a luminous body, it is nbn-luminous body. It has no light of its own.

Question 7.
What do we call a body that shmes on its own ?
Answer:
The bodies that shines onits ownor whichthemselves emittheir own light are called the luminous bodies.

Question 8.
What do we call an electric bulb producing light ?
Answer:
Luminous object.

Question 9.
What is a transparent medium ? Give two examples.
Answer:
Amedium which allows the passage of light through it easily,is called a transparent medium.
Examples: glass, air, water etc.

Question 10.
Explain the difference between a transparent, a translucent and an opaque medium. Give two examples of each.
Answer:

1. Transparent objects — Those objects through which light can pass easily are called transparent obj ects. e.g. Water, glass, air.
2. Translucent object— The ohj ect through which light can pass partially are called translucent object, e.g. tracing paper, waxed paper.
3. Opaque object— The objects which do not allow the light to pass through are called opaque objects, e.g. wood.

Question 11.
What do we call a substance through which we cannot see light ? Give an example of such a substance.
Answer:
A substance through which we cannot see light is called an opaque medium.
Examples:  Wood, metals, butter paper and black paper etc.

Question 12.
What do we call a substance through which light passes ? Give an example of such a substance.
Answer:
A substance through which light passes is called a transparent substance.
Examples: glass, air, water etc.

Question 13.
Can a transparent medium form an image ? Explain your answer.
Answer:
No, a transparent medium cannot form image. All the light that passes through a transparent medium completely pass through the substance. For the formation of image it is must that the light rays get reflected through the surface.

Question 14.
How can you obtain a point source of light ?
Answer:
A point source of light is obtained either by placing a screen having a fine hole, in front of die luminous body or by placing the luminous body inside a box having a fine hole on one of its side.

Question 15.
Define the terms : a ray of light and a beam of light.
Answer:
The light travelling in any one direction in a straight line is called a ray of light.

A group of light rays given out from a source is called a beam of light

Question 16.
What do you mean by ‘rectilinear propagation of light’ ?
Answer:
Light travels in a straight line path. This is called the rectilinear propagation of light.

Question 17.
Describe an experiment to show that light travels in a straight line path.
Answer:
Take three cardboards A, B and C each about 25 cm square. Take a pin and make a small hole in each cardboard at the same height. Suspend the cardboard pieces by separate threads vertically from a support such that each hole is at the same height, as shown. Pass a string through the holes and pull it taut. This makes the three holes in a straight line. Now take out the string.
Place a lighted candle near one of the cardboards (say A). Look at the candle flame from the other side of the cardboard C. The candle flame is clearly seen.
Now slightly displace one of the cardboards (say B) so that the holes no longer remain in a straight line. Again look at the candle flame from the other side of the cardboard C. You do not see the candle flame. The reason is that light travels in a straight line and now the holes in the cardboards A, B and C are not in a straight line.
Conclusion: Light travels in a straight line path called the rectilinear propagation of light.

Question 18.
In which of the following two arrangements (a) and (b) shown in the diagram, you can see the light of the bulb ? Explain Your answer

Answer:
We can see the light of the bulb in the arrangement (a).
This is so because in arrangement ‘a’ the rod is straight and light travels in a straight line path.
Whereas in arrangement ‘b’ the rod is bent. So the light cannot pass through it.

Question 19.
Name a simple application of the rectilinear propagation of light
Answer:
The simple applications of rectilinear propagation of light are pin hole camera, formation of shadows and elipses.

Question 20.
What is a pin hole camera ? Draw a neat and labelled diagram to show the formation of image of a lighted candle by it.
Answer:
The pin hole camera is a simple application of the rectilinear propagation of light.

Question 21.
Explain the formation of image of a luminous object in a pin hole camera with the aid of a neat diagram.
Answer:
When a luminous object AB, such as a lighted candle, is placed in front of the pin hole, an inverted picture A’ B’ of the candle is
obtained on the tracing paper. This picture A’ B’ is called the image. The image obtained is upside down (i. e. inverted). The reason is that the light travels in a straight line path. Hence light from the upper point A of the candle passes through the pin hole and strikes
the tracing paper at A’. Similarly, light from the lower point B of the candle passes through the pin hole and strikes the tracing paper
(or screen) at B’. Light from all the other points between A and B, on passing through the pin hole strikes the tracing paper in between
A’ and B’. As a result, an inverted image of the candle is seen on the tracing paper Fig shows the simple ray diagram for die formation of image.

Question 22.
State two factors which affect the size of image formed in a pin hole camera.
Answer:
Factors affecting the size of the image :
The size of image depends on the following two factors:

1. The distance of screen (i.e. tracing paper) from the pin hole, and
2. The distance of obj ect (i.e. candle) in front of the pin hole.

Question 23.
Is the image obtained in a pin hole camera erect or inverted ? Give reason for your answer.
Answer:
Image obtained in a pin hole camera is inverted.
The reason is that the light travels in a straight line path. Hence light from the upper point of the candle passes through the pin hole and strikes the tracing paper in the lower point. Similarly light from the lower point of the candle passes through the pin hole and strikes the tracing paper at the upper point.

Question 24.
How is the image affected in a pin hole camera when another fine hole is made near the first pin hole ?
Answer:
If another pin hole is made near the first pin hole, two images are formed on the screen, one due to each of the two pin holes. If the holes are very close, the two images tend to overlap each other. As a result, a blurred image will be seen.

Question 25.
State the effect on the image in a pin hole camera if

1. The hole is made bigger.
2. The luminous object is moved towards the pin hole.
3. The length of the pin hole camera is increased (le. the screen is moved away from the pin hole).

Answer:

1. If the hole is bigger than a pin hole, again a blurred image in seen. The reason is that a bigger hole is equivalent to a large number of pinholes. Each pin hole produces one image. These images overlap each other resulting in a blurred image.
2. If the object is moved towards the pin hole the size of the image increases.
   The size of image / The size of object = Distance of screen from pin hole / Distance of object from pin hole
3. When the length of the pin hole camera is increased. C is the screen is moved away from the pinhole, the size of image also increases.

Question 26.
What is a shadow ? Give a reason for its formation.
Answer:
Shadow : When light falls on an opaque object, light is obstructed and a dark patch on a screen kept behind is called shadow. This is because light propagates in straight line. If distance between obj ect and screen is less, the shad o w will be (umbra) dark and smaller.
If the distance is increased shadow will be dim and larger.

Question 27.
Draw a ray diagram to show the formation of shadow of an opaque object by a point source of light. How is the size of shadow affected if the screen is moved away from the object?
Answer:

If we move the screen away from the object, the shadow increases in size.

Question 28.
State two differences between an umbra and a penumbra.
Answer:
Umbra

1. It is the portion of shadow where no light reaches from the source of light due to the opaque object.
2. It is completely dark.

Penumbra
It is the portion of shadow where a portion of light from the source of light reaches the shadow even in the presence of the opaque object in between them.
It is not completely dark, but is dim (or less bright).

Question 29.
Draw a ray diagram to show the formation of umbra alone.
Answer:
Formation of umbra alone.

Question 30.
Draw a ray diagram to show the formation of umbra and penumbra both. Label the parts umbra and penumbra in your diagram.
Answer:
If your move the screen away from the object, the shadow increases in size. Formation of umbra and penumbra both.

Question 31.
In each of the following diagrams, draw rays to form umbra and penumbra on the screen.
(a)

(b)

Answer:
(a)A’B’—umbra
Umbra alone is obtained on the screen when the opaque object is illuminated by a point source of light.

(b)

EF is Penumbra CD is umbra.

Question 32.
State the conditions when only the penumbra of an opaque object is obtained on the screen.
Answer:
If the size of source of light is bigger than the size of the opaque object, the size of umbra is very small. If the screen is moved away from the object, the umbra vanishes and only the penumbra remains.

Question 33.
Why is it that the birds flying in the sky do not cast their shadow on the earth ?
Answer:
We do not see the shadow of a bird flying high up in air because in their shadow, the umbra is absent and the penumbra is too large and too faint that it is not visible as the distance of screen (i.e. earth) is very large from the object (i.e. bird).

Question 34.
Why are shadows at noon shorter than in the morning or in the evening ?
Answer:
At noon the sun is directly overhead. So, the sun rays fall vertically on the body. Hence the shadow is very short. In the morning and evenings, the sun rays fall in an inclined position. So, the shadows are long.

Question 35.
What is an eclipse ? Name the two types of eclipses.
Answer:
Eclipses are the examples of formation of shadows in nature. There are two kinds of eclipses:

1. Lunar eclipse (the eclipse of the moon), and
2. Solar eclipse (the eclipse of the sun).
   Lunar eclipse is due to the formation of shadow of earth on moon and solar eclipse is due to the formation of shadow of moon on earth.

Question 36.
When does a lunar eclipse take place ? Does it occur on every full moon’s night ?
Answer:
A lunar eclipse occurs when the earth comes in between the sun and moon and casts its shadow on moon. On a full moon night, the moon rises in the east after sun sets in the west. On such a night, the sun and moon are on the opposite sides of the earth. The shadow of the earth falls on the surface of the moon therefore moon is not visible to us. This is lunar eclipse as shown in the figure.

Question 37.
Draw a diagram to show the formation of lunar eclipse.
Answer:

Question 38.
When does a solar eclipse take place ? Does it occur on even’ new moon’s day ?
Answer:
Solar eclipse— On a certain moon’s day the moon, happens to come in between the sun and the earth. They come in a straight line. In such a situation, the moon being smaller in size casts its shadow only on a limited region on the earth. In these regions of the earth, the solar eclipse occurs.

Question 39.
Draw a diagram to show the formation of solar eclipse.
Answer:

Question 40.
What is annular solar eclipse ? Draw a labelled diagram to show its formation.
Answer:
An annular solar eclipse occurs when only the tip of the umbra of the moon falls on the earth. From the point D, the sun will appear to be completely obstructed by the moon, only the outer rim of the sun, called corona, is then visible for a very short time which is known as the diamond ring. The formati on of annular solar eclipse is shown below.

ICSE Solutions for Class 6 Geography Voyage – Minerals and Ores

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POINTS TO REMEMBER

• Minerals are substances that are naturally present in the earth and are not formed from animal or vegetable matter.
• An ore is a naturally occurring solid material from which a mineral, generally a metal, can be profitably extracted.
• Minerals are generally classified as metallic and non-metallic minerals.
• Metallic minerals include iron ore, uranium, bauxite, manganese, gold, silver and copper.
• Non-metallic minerals include limestone, mica, coal and petroleum.
• Mining is the process of taking out minerals and other substances from the earth.
• There are two types of mining—surface mining and underground mining.
• It is important to conserve minerals as they take thousands of years to form.

IMPORTANT TERMS

Ferrous minerals : Minerals which contain iron, such as iron ore, manganese and chrome.
Non – ferrous minerals : Minerals that do not contain iron, such as gold, silver, copper and lead.
Ore : A naturally occurring solid material from which a particular mineral, usually a metal, can be profitably extracted.

THINK AND ANSWER

How would our life be affected if coal, petroleum and natural gas were exhausted in the next 30 years ?
Answer:
If all the exhaustible natural resources are exhausted by human activities, then the survival of living beings would not be possible. Actually, fossil fuels are the most important source of energy for us today.
They are concentrated source of energy and give offheat and light on burning. The heat can be used to cook food or to run engines such as automobile engines. It can be used to generate electricity as in powerhouse where the most common fuel used is coal. Everything will not be available.

VALUES AND LIFE SKILLS

Conventional energy resources—coal and petroleum— are very important for a country. Therefore, we need to be careful while using them.
Can you suggest some ways by which we can reduce the use of conventional energy resources ?
Answer:

1. Use more energy efficient by using energy saver products like LED lights etc.
2. Use Bicycles for shorter distances instead of cars or bikes.
3. Switch off the lights when not required.

EXERCISES

A. Fill in the blanks

1. All rocks are composed of minerals.
2. Minerals are obtained by a process called mining.
3. Metallic minerals are generally found in igneous rocks.
4. Ferrous minerals contain iron.
5. Peat has very little carbon.

B. Write true or false

1. Metals can be profitably extracted from ores.
Answer. True.

2. Metallic minerals are generally found in sedimentary rocks.
Answer. False.
Correct — Metallic minerals are generally found in igneous rocks.

3. Bauxite is the lightest metal.
Answer. True.

4. Bituminous coal has the highest carbon content.
Ans. False.
Correct — Anthracite coal has the highest carbon content.

5. Mica is a metallic mineral.
Ans. False.
Correct— Mica is a non-metallic mineral.

C. Match the columns

Answer:

D. Answer the following questions in brief:

Question 1.
What is a mineral ?
Answer:
Minerals are substances that are naturally present in the earth and are not formed from animal or vegetable matter.

Question 2.
Name a few minerals.
Answer:
Diamonds, quartz, topaz, gypsum, iron, copper, bauxite, zinc, gold, silver, manganese, etc.

Question 3.
What is an ore ?
Answer:
An ore is a naturally occurring solid material that contains a large amount of a particular material, using a metal which can profitably extracted, eg. iron ores, copper ores, bauxite (from which aluminium is extracted) zinc, etc.

Question 4.
What is the main difference between a ferrous and a non- ferrous mineral ?
Answer:
Ferrous minerals :

1. These minerals contain iron.
2. They have high tensile strength.
3. Examples: Iron ore, manganese and chrome.

Non-ferrous minerals :

1. These minerals does not contain iron.
2. They have low tensile strength.
3. Examples: Gold, silver, copper and lead.

Question 5.
Mention any two characteristics of iron ore.
Answer:
The most important mineral in the world is iron ore. It is known for its hardness, strength and ductility (it can be made or stretched into a thin wire).

Question 6.
Mention the different types of iron ore.
Answer:
There are four different types of iron ores-haematite, magnetite, limoniteandsiderite.

Question 7.
What is surface mining ?
Answer:
When the top layer of soil is removed and the rocks that lie underneath are extracted with the help of heavy machinery is called surface mining. Surface mining is done to extract minerals that are found close to the surface such as coal and some kinds of sedimentary rocks like limestone and mica.

Question 8.
Mention any three uses of coal.
Answer:
Coal is used for various purposes like cooking, heating and producing electricity, and in various industries.

E. Answer the following questions in one or two paragraphs

Question 1.
Differentiate between metallic and non-metallic minerals.
Answer:
Metallic Minerals :

1. These minerals contain metals, which are hard substances.
2. These minerals found in igneous rocks.
3. Examples: Iron ore, bauxtie, manganese and copper, etc.

Non-metallic Minerals :

1. These minerals does not contain extractable metals.
2. These minerals found in sedimentary rocks.
3. Examples: Coal, potash, limestone, gypsum, mica, etc.

Question 2.
Give an account of iron ore production in the world.
Answer:
Iron is the main metal used for making steel, which is used in almost all industries. The main producers of iron are China (42%), Australia (22%), Brazil (10%), South Africa, etc. India produces about 4% of total iron ore. Main states in India are Odisha, MP, Jharkhand, AndhraPradesh, Tamil Nadu.

Question 3.
Give any three uses of copper.
Answer:
Uses of copper are :

• Copper is mainly used in making electric and telephone wires.
• It is also used in making pipes and coins.
• Alloys such as brass and bronze are made using copper.

Question 4.
What are the two types of mining ? Elaborate on the differences between the two.
Answer:
The two types of mining are:

1. Surface mining — It is the removal of top layer of soil and rocks, to extract the minerals lying underneath is called surface mining. Surface mining is done to extract minerals that are found close to the surface such as coal and some kinds of sedimentary rocks like limestone and mica.
2. Underground mining — It is the one in which a shaft is dug which is long, narrow passage and vertically deep into the ground and then people or heavy machinery is sent down, the tunnels are blasted using dynamite to extract the minerals, eg. gold, silver, etc.
   In surface mining, the top layer of the soil is removed, large pits or holes are dug and the rocks that lie underneath are extracted with the help of heavy machinery. These pits are called open cast mines or quarries. Open cast mining is a common form of coal mining in India.
   In surface mining, trees and other natural vegetation are destroyed. Surface mining is done to extract minerals that are found close to the surface such as coal and some kinds of sedimentary rocks like limestone and mica.
   Underground mining: In underground mining, a shaft, which is a long, narrow passage, is dug vertically deep into the groud. People and machinery are then sent down through this shaft. Sometimes, after after descending into the shaft, tunnels are blasted into the earth with the help of dynamite. Then the men and machines move about through these tunnels to take out things such as coal, gold, silver, tin, lead and copper. Underground mining causes sinking of the land, underground water pollution and surface water pollution, among other things.

Question 5.
Describe the importance of minerals.
Answer:
Minerals play an important role in our daily lives. A number of things of our daily use such as door knobs, latches, window grills, utensils, etc. are made of minerals. Iron and its alloy, steel, is used in making bridges, buildings, and wide range of machines and tools, which have made our life simpler and easier. Copper wires are used in our electrical and electronic gadgets. Copper tools and utensils are also widely used. Gold and silver are used in making our jewellery. Aluminium extracted from bauxite is used to make aeroplanes, our fastest means of transport. Mica is used in electrical goods and limestone is used as cement in constructing houses and buildings.
Coal, petroleum and natural gas are important energy or power resources. Coal is used for various purposes like cooking, heating and producing electricity, and in various industries. Once petroleum is refined, we obtain different products such as petrol, diesel, kerosene, cooking gas, etc. Vehicles such as cars, trucks, trains, etc. run on petrol and diesel. Kerosene is used for cooking and other purposes. Products such as plastics and cosmetics are also made from petroleum. Natural gas is used as a fuel in cars, buses, etc. and hence are important for the agricultural sector as well.

Question 6.
Why is it important to conserve minerals ?
Answer:
Minerals are important for every country for its development and they need to be conserve because :

1. Minerals are non-renewable resources which once used can’t be obtained again as it takes thousands of years to form.
2. Workable minerals are in insufficient quantities (just 1 % of the earth’s crust)
3. We are rapidly consuming mineral resources that requires millions of years to be renewed.
4. Industry and agriculture depend upon minerals and the substances manufacture from them.

F. Picture study.

Look at this picture of the inside of an iron and steel industry and answer the following questions

Question 1.
Which are the major producers of iron and steel in Asia?
Answer:
China produces almost 45 per cent of the total world production of Iron and Steel.

Question 2.
Which states in the south of India produce a large quantity of iron and steel ?
Answer:
Andhra Pradesh and Tamil Nadu are the major iron-producing states.

ICSE Solutions for Class 6 Geography Voyage – South America : Location, Area, Political and Physical Features

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 6 Geography Voyage. You can download the Voyage Geography ICSE Solutions for Class 6 with Free PDF download option. Geography Voyage for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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POINTS TO REMEMBER

• The Isthmus of Panama joins South America to North America. South America is triangular in shape and a greater part of it lies south of the equator.
• South America can be divided into four physical divisions—the West Coastal Plains, the Andes Mountains, the Central Plains and the Eastern Highlands.
• The West Coastal Plains are narrow plains lying between the Pacific Ocean and the Andes Mountains, in the western part of the continent. The Atacama Desert is located here.
• The Andes are a long stretch of high, young fold mountains that run parallel to the Pacific Coast in the western part of the continent. Mt Aconcagua, the highest peak in South America, and Lake Titicaca, the second highest freshwater lake in the world, are located here. There are also several active dormant volcanoes located here such as Mt Chimborazo and Mt Cotopaxi.
• The Central Plains are lowlands that lie between the Andes in the west and the Eastern Highlands in the east. The flat plains are formed by the rivers Amazon, Orinoco, Parana, Paraguay and Uruguay.
• The Guiana Highlands and the Brazilian Highlands form the Eastern Highlands. The two highlands are separated by the river Amazon. These highlands extend in the eastern part of the continent along the Atlantic coast.
• The Orinoco River, the Magdalena River and the Amazon River are some of the important rivers of South America. Rivers Paraguay, Parana and Uruguay form the La Plata river system. Lake Titicaca, Lake Poopo and Lake Maracaibo are the important lakes of die continent.

IMPORTANT TERMS

Llanos : The grasslands of the Orinoco Basin.
Selvas : The dense equatorial forest of the Amazon Basin.
Pampas : The extensive temperate grasslands of Argentina.

VALUES AND LIFE SKILLS

We must learn not to exploit natural resources and to instead, take care of our environment and the natural resources we have, like the indigenous people in the Amazon Basin
What are the ways in which you can encourage a sustainable lifestyle ?
Answer:
We can encourage a sustainable lifestyle by following ways :

1. Become a member of a community garden.
2. Change the lights in your house (from light bulbs to CFL).
3. Become more efficient with your errands.
4. Start using Natural cleaners.
5. Walk, bike or car pool to work.

EXERCISES

A. Identify who I am

1. I am a narrow neck of land that joins South America to North America and separates the Atlantic Ocean from the Pacific Ocean : Isthmus of Panama.
2. I am a hot desert that lies in the western coastal region of South America and stretches across the Tropic of Capricorn : Atacama desert.
3. I am one of the few gaps in the Andean Mountain chain : Uspallata Pass.
4. I am the highest peak of the second highest young fold mountain chain of the world, with a height of6,960 metres above sea level : Mt. Aconcagua.
5. I am the second highest freshwater lake in the world : Lake Titicaca.

B. Write true or false.

1. The 60° W longitude passes almost through the middle of South America.
Answer. True.

2. The Orinoco Plains are called the llanos.
Answer. True.

3. The selvas are another name for the grasslands of Argentina.
Answer. False.
Correct— The pampas are another name for the grasslands of Argentina.

4. The La Plata river system drains southwards into the Atlantic Ocean.
Answer. True.

5. Lake Titicaca and Lake Poopo are saltwater lakes.
Answer. False.
Correct — Lake Titicaca and Lake Poopo are freshwater lakes.

C. Match the columns

Answer:

D. Answer the following questions in brief

Question 1.
What is the latitudinal extent of South America ? In which hemisphere does the major part of it lie ?
Answer:
South America extends from 12°N to 55°S and from 35°W and 81°W. Major part of this continent lies in Southern hemisphere though some parts lie north of the equator.

Question 2.
Name the water bodies that lie to the east and the west of this continent.
Answer:
The continent is bounded by Pacific ocean in West, Atlantic Ocean in East. The Caribbean sea lies north of this continent and it stretches as far South as the Southern Ocean.

Question 3.
Identify the major physical divisions of South America.
Answer:
The major physical divisions of South America are:

• The West Coastal Plains.
• The Andes Mountains.
• The Central Plains.
• The Eastern Highlands.

Question 4.
In what respect is the Atacama Desert different from the Patagonian Desert ?
Answer:
Atacama desert is a hot desert which lies in the Western Coastal Region across the Tropic of capricorn in North Chile whereas Patagonian desert is a cold desert which lies between 40°S and 50°S in Argentina in eastern highlands.

Question 5.
Name three Andean towns that are also capital cities in South America.
Answer:
Bogota, the capital of Colombia; Quito, the capital of Ecuador, and La Paz, the capital city of Bolivia, are important towns. Cuzco, the old Inca capital, Oroya in Peru, and Potosi in Bolivia are also important cities.

E. Answer the following questions in one or two paragraphs

Question 1.
Describe the Andes under the headings :

• Extent
• Position
• Features
• Significance

Answer:

• Extent — Long stretch of young fold mountains that run parallel to pacific coast in Western part of South America.
• Position — They are not one mountain range but several parallel ranges with basins and plateaux between them lying in the West Coastal region of South America.
• Fcatures — Despite being near the equator, the highest peak. Mt. Aconcagua remains snow covered. The Uspallata Pass is one of few gaps in the lofty mountain range. Lake Titicaca is the highest freshwater lake found in Andes. There are many active volcanic mountains present in Andes as they form a part of Pacific Ring of fire.
• Significance — Andes are storehouse of mineral wealth like copper, gold, silver, tin, lead and platinum. Many short, swift rivers flowing down the Andes supply hydroelectricity.

Question 2.
Explain the following : llanos, selvas, pampas and the Gran Chaco.
Answer:

1. Llanos — The Orinoco Plains are called llanos which means plains in Spanish.
2. Selvas — The Amazon Lowlands are called selvas.
3. Pampas — The temperate grassy plains of Argentina are called pampas.
4. Gran Chaco — The vast alluvial region which is not drained well and become marshy during rainy season in Parana- Paraguay lowlands are called Gran Chaco.

Question 3.
How are the Eastern Highlands different from the Andes Mountains ?
Answer:
The Eastern highlands are much lower in height than the Andes. The Andes are young fold mountains having active volcanic erruptions whereas the Eastern highlands are composed of old hard rocks and have Patagonian Desert which is a cold desert.

Question 4.
Describe the Amazon, the largest river of South America.
Answer:
The Amazon River rises in the Andes Mountains and flow Westward across the widest part of the continent. This is the largest river in the world. The equator passes near the mouth of this river. It divides the Guiana Highlands and the Brazilian highlands.

Question 5.
Describe the La Plata river system.
Answer:
The flat plains that are formed by the Parana, Paraguay and Uruguay rivers collectively is called La Plata river system. These rivers flow southwards and drain into the South Atlantic Ocean in a wide estuary in Argentina, which provides on excellent harbour.

F. On a blank outline map of South America mark and name the following :

1. Isthmus of Panama and Cape Horn
2. Rivers Amazon, Paraguay, Uruguay and Orinoco
3. Selvas, pampas, Guiana Highlands and Brazilian Highlands
4. Mountain peaks — Aconcagua, Cotopaxi and Chimborazo
5. Lake Titicaca and Lake Poopo

Answer:

G. Picture study
The picture here shows the world’s highest waterfall, which is in South America.

Question 1.
Identify the waterfall.
Answer:
Angel Falls.

Question 2.
Which river forms this waterfall ?
Answer:
The world’s highest waterfall ‘Angel Falls’ are formed by tributary of the river Orinoco.

ICSE Solutions for Class 6 Geography Voyage – Major Landforms of the Earth

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 6 Geography Voyage. You can download the Voyage Geography ICSE Solutions for Class 6 with Free PDF download option. Geography Voyage for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

ICSE Solutions Class 6 GeographyHistory & CivicsBiologyChemistryPhysicsMaths

POINTS TO REMEMBER

• Nearly 29 per cent of earth’s surface is land.
• Land features on the surface of the earth are different in different places. These features are called landforms. The major landforms include mountains, plateaux, valleys and plains.
• There are three main types of mountains—fold mountains, volcanic mountains and block mountains.
• There are two types of fold mountains—old and young.
• Plateaux are also called plains-in-the air or tablelands.
• Plains are flat lowlands that are mostly built by the alluvium deposited by rivers.

IMPORTANT TERMS

Fold mountains: Mountains that are formed when horizontal layers of the earth’s crust are folded by compression.
Landforms: Features of the land surface.

Discuss

Formation of landforms is a continuous process. Discuss the different ways in which landforms are changing around the world.
Answer:
The earth’s surface is constantly changing. These changes mostly occur in very minute ways which over time accumulates to create the earth’s physical features. Whereas some of these changes take thousands of years but surely they are occuring. We look around us that a mountain, river, plateau, valleys, rqck boulders etc. these all didn’t just disappear suddenly rather most of them had a building process.
There are basically two types of changes that occur on the earth’s surface.

1. Slow change
2. Fast change.

Fast change occur through the actions of earthquakes, volcanoes, landslides etc. While slow change takes time and has a process.

VALUES AND LIFE SKILLS

We constantly impact landforms around us by our actions such has mining, building roads, dams, etc. We should, therefore, try to minimize such activities that have an adverse impact on landforms around us.
How can you help to preserve the landforms around you?
Answer:
We can preserve the landforms around us by adopting following methods, and they are :

1. By Planting More Trees and Not cutting them.
2. By Properly Disposing the Industrial waste.
3. By Preserving greenery surrounding, National Parks and Wildlife Sancturies.
4. Avoid de-vegetating the landforms and its Vicinity, if that’s it’s natural condition.
5. Replicate Natural landscapes, patterns and processes.

EXERCISES

A. Match the columns


Answer:

B. With the help of your atlas identify and mark the following in an outline map of the world.

Question 1.
An old fold mountain range in India.
Answer:
Aravallis

Question 2.
A block mountain in Europe
Answer:
The Black Forest of Europe.

Question 3.
A storehouse of mineral wealth in eastern india.
Answer:
The Chota Nagpur Plateau.

Question 4.
A rift valley in Egypt
Answer:
NileValley in Egypt.

C. Answer the following questions in brief

Question 1.
What are fold mountains? With the help of a neat-sketch, briefly explain their formation.
Answer:
The mountains that are formed when the layers of the earth’s crust are folded by compression caused by the forces generated by movements inside the earth.

There are particularly two types of fold mountains, they are :

1. Old fold mountains
2. Young fold mountains.

Question 2.
State two chief differences between old and young fold mountains. Give examples.
Answer:
The mountains which were formed over 250 million years ago due to compression of earth’s crust are called old fold mountains. They have gentle slopes and low altitude due to weathering overtime eg. Urals in Russia, Aravallis in India and Appalachians in India.
The recently formed mountains i.e. about 25 million years ago are called young fold mountains. They are rugged and lofty. They comprise the world’s highest mountain ranges.
Eg. Rockies of North America, Alps, Andes, Himalayas and The great Dividing Range.

Question 3.
What are plateaux ? Why are they of great economic value?
Answer:
Plateaux (plural of plateau) are the uplifted sections of the earth’s crust that are almost flat or level and usually descend steeply to the surrounding lowlands. Aplateau is also sometimes referred to as a plain-in-the air or tableland. The land of a plateau is very fertile while the latter is a storehouse of mineral wealth. They are rich in minerals like gold, iron, copper, manganese, etc.

Question 4.
Mention the different types of plateaux.
Answer:
Types of Plateaux — Plateaus may be classified into the following categories on the basis of their formation, appearance and location:
Tectonic Plateau : A tectonic plateau is formed by the movement of the earth’s crustal plates. Tectonic movement causes a huge portion of the earth’s surface to rise. The plateau of South Africa and the Turkish-Iranian Plateau are examples of tectonic plateaus.
Volcanic Plateau : A volcanic plateau is a plateau formed by the spread of successive layers of lava on a particular region. When the lava cools, it solidifies and the successive sheets of lava finally form a raised tabeland or a plateau over a period of time. The extensive Columbia Plateau (in the north-western part of the U SA), the north-western part of the Deccan Plateau and the Malwa Plateau are examples of volcanic plateaus.
Dissected Plateau : These have irregular surface marked by canyons, gorges and steep, narrow valleys formed by the process of erosion. They are mostly common in dry and desert regions. The Colorado Plateau, through which the Grand Canyon passes, and the Brazilian Plateau (Mato Grosso) are examples of dissected plateaus.
Intermontane Plateau : These are surrounded by mountains and are the most common types of plateau. The most common example of an intermontane plateau is the Tibetan Plateau which is enclosed by the Himalayan Mountains to its south and the Kunlun Shan to its north.
Piedmont Plateau : Piedmont plateau is one that lies between a mountain and a plain or an ocean. Examples of piedmont plateaus are the Patagonia Plateau in South America and the piedmont Plateau of North America.

Question 5.
What is a basin ? Give an example.
Answer:
A basin is a depressed section of the earth’s crust surrounded by higher land. Many basins are found alongside plateau edges and form areas of inland drainage, i.e., the rivers flowing in the basin do not reach reach the sea. The Tarim and Tsaidam Basins of Asia and the Chad Basin ofnorth-central Africa are examples ofbasin.

Question 6.
Mention the different types of plains.
Answer:
Types of Plains: On the basis of formation, plains are grouped in three categories:
Structural Plains: Plains that lie near the coast of a sea or an ocean are called structural plains. Due to endogenetic movements, large, broad, flat areas of the sea floor are raised and appear on the surface. These types of plains are very flat and broad. The addition of sediments brought in by the sea waves over a period of time makes them broader and flatter than they originally were. Structural plains border all countries. The coastal plains of south-eastern USA near the Gulf Coast, which are part of the Great Plains, are one of the largest plains in the world. The plains of northern Russia and the central lowlands of Australia are other examples of structural plains.
Erosional Plains: Erosional plains are the result of the erosion of mountains, hills and plateaux. The eroded material is brought down to a low level by wind, rivers, rain, and ice. This kind of erosion caused by various agents gives rise to several types of plains. The plains of northern Canada, northern Europe and Kashmir in India are examples such plains.
Depositional Plains : Depositional plains are formed by sediments brought down on a large scale by natural agents such as moving ice, water and wind from the upper regions of mountains.

Question 7.
What is the importance of plains ?
Answer:
The importance of the plains are discussed below:

1. Plains are important because they are good source of fresh fruits and vegetables.
2. Plains are being ploughed by a farmer or a carabaos.
3. Owing to the flat nature of the land. It is easy to construct roads and railways in plains.
4. Plains have good and rich source of river which is very fertile for crops.

Question 8.
What is a peninsula ? Take the help of your atlas and name four major peninsulas of the world.
Answer:
A Peninsula is a piece of land that is surrounded by water on three sides and joined to a larger land mass. The peninsular plateau of India and the Malay Peninsula are two examples of peninsulas attached to the continent of Asia. Europe is a peninsula of peninsulas. Can you name the three large water bodies that surround it ? Also identify the smaller peninsulas that jut out from it.
Arabian peninsula, Deccan for major peninsula are peninsulas, Indo-China peninsula, Alaska peninsula.

Question 9.
Which two land masses does the Isthmus of Panama connect ?
Answer:
The Isthmus of Panama joins North America and South America with the Pacific Ocean on one side and the Atlantic Ocean on the other. The Isthmus of Suez joins Africa to Asia and separates the Mediterranean Sea and the Red Sea.

D. Answer the following questions in one or two paragraphs :

Question 1.
Name the major landforms on earth.
Answer:
The major landforms on earth are :

• Mountains — Most of the rivers originate from mountains. They are rich in minerals and metals deposits and support variety of flora and fauna.
• Plateau — They are storehouses of minerals such as gold, silver, iron, copper, manganese, etc.
• Valley — They are low-lying lands between hills formed by river flowing down the mountains or due to movement of earth plates.
• Plains — They are the most fertile landforms which support easy habitation.

Question 2.
List the continents according to size. Describe the two largest continents in detail.
Answer:
Continents are very large land masses that are surrounded by vast water bodies called oceans on all sides. They are the primary divisions of land. There are seven continents in the world.
Asia is the largest continent. It occupies about one-third of the land area of our planet. It is joined to the land mass of Europe and, thus, we use the term Eurasia for this combined land mass. The Ural Mountains, the Black Sea and the Caspian Sea separate the two continents. We find oceans on three sides of this land mass. To its north lies the Arctic Ocean, to its east is the Pacific Ocean and to its south is the Indian Ocean.
Africa is the second largest continent after Asia. It is surrounded by water bodies on all sides. In the north, the Mediterranean Sea separates it from Europe, and on its east is the Indian Ocean. The Atlantic Ocean in the west separates it from the two Americas. In Africa lies the largest desert of the world, the Sahara Desert.

Question 3.
Write short notes on

1. Europe
2. Australia.

Answer:

1. Europe is smaller in size in comparison to the other continents mentioned above but has some of the most developed nations in the world. To its north is the Arctic Ocean. The Atlantic Ocean separates it from North America. It has the most indented coastline among the continents, which is why it has numerous ports and some of the finest harbours in the world.
2. Australia is sometimes called ‘the Land Down Under’ as it lies to the south of the main land masses. It is also the smallest continent in size. As there is water on all sides—the Indian Ocean in the west, the South Pacific Ocean in the east, the Southern Ocean in the south, and the Arafura Sea in the north— it is an island and is, therefore, also called the ‘island continent’.

Question 4.
How is Mount Fuji of Japan different from the Vosges of Europe ?
Answer:
Mount Fuj i is a volcanic mountain formed when molten lava, ash, dust, etc. come out through cracks in earth’s crust and is accumulated in shape of high cone. Where as Vosges in Europe are formed by rupturing or fracturing of rock strata due to strain and is an example of block mountain.

Question 5.
Briefly describe the importance of mountains.
Answer:
Importance of Mountains:

1. Mountains are a storehouse of water. Many rivers originate in the glaciers in the mountains.
2. Reservoirs are made and the water from the mountains is used for irrigation and generation of hydro-electricity.
3. The river valleys and terraces are most suitable for farming and cultivation of crops as the land is very fertile.
4. Mountains support a rich variety of flora and fauna.
5. Mountains also affect the climate of an area.
   For example, the Himalayas cause rainfall in India by blocking the south-west monsoon winds. They also protect us from the cold winds of Central Asia in winter.
6. Mountains are also rich in mineral and metal deposits which are essential for industries.
7. According to the United Nations Development Programme, mountains provide home for around 720 million people.
8. The forests in the mountainous regions provide fuel, fodder, shelter and other products like gum, wild fruits, mushrooms, resins, etc. mountains provide an ideal holiday for tourists. They visit the for their natural scenic beauty and relaxation.
9. Many recreation, sporting and tourism activities takes place in the mountains. Paragliding, hang gliding, river rafting and skiing are popular sports in the mountains.

Question 6.
How is a volcanic mountain formed ?
Answer:
Volcanic mountains are formed when molten lava, ash, cinder and dust from deep inside the earth come out on the surface through cracks in the earth’s crust and accumulate in the shape of high cones.
The opening through which lava and other materials come to the surface is called a vent. The funnel-shaped depression at the top of a vent is called a crater.
Examples – Mountain Fujiyama in Japan, Mountain Mayon in the Philippines.

Question 7.
What is a V-shaped valley ?
Answer:
The valley which is formed by an exogenous process i.e. from the outside like a river flowing down the mountain eroding the soil and minerals form a V-shaped valley, eg. Rhine valley in Europe and Damodar valley in India.

Question 8.
Briefly explain

1. peninsula
2. island
3. isthumus.

Answer:

1. Peninsula: is a piece of land that is surrounded by water on three sides and joined to a larger land mass. The peninsular plateau of India and the Malay Peninsula are two examples of peninsulas attached to the continent of Asia. Europe is a peninsula of peninsulas. Can you name the three large water bodies that surround it ? Also identify the smaller peninsulas that jut out from it.
   Arabian peninsula, Deccan for major peninsula are peninsulas, Indo-China peninsula, Alaska peninsula and Labrador peninsula.
2. Island : An island is a piece of land which is surrounded on all sides by water. India has two groups of islands – the Lakshadweep Islands in the Arabian Sea and the Andaman and Nicobar Islands in the Bay of Bengal.
3. Isthumus : An isthmus is an elongated narrow piece of land, with water on each side, that joins two large land masses. For example, the Isthmus of Panama joins North America and South America with the Pacific Ocean on one side and the Atlantic Ocean on the other. The Isthmus of Suez joins Africa to Asia and separates the Mediterranean Sea and the Red Sea.

E. Draw neat, labelled, coloured sketches to show the characteristics of each of the following geographical features. Write a brief description alongside, explaining each of them

Question 1.
Block mountain
Answer:
Block mountain—They are formed by rupturing or fracturing of rock strata due to strain. The land between the cracks inside the earth sink leaving upstanding blocks on either side making mountains.

Question 2.
Volcanic mountain
Answer:
Volcanic mountain — They are built when molten lava, ash, cinder and dust from deep inside the earth comes out on the surface through cracks in the earth’s crust and accumulate in the shape of high cones.
The opening through which lava and other materials come to the surface is called a vent. The funnel-shaped depression at the top of a vent is called a crater.

Question 3.
Plateau
Answer:
Plateau — It is the uplifted section of the earth’s crust that are almost flat or level and usually descend steeply to the surrounding lowlands, eg. Deccan Plateau and the Chota Nagpur plateau etc.

Question 4.
Rift valley
Answer:
Rift Valley—The rift valley is the type of valley that is formed when the land between the two faults sink i.e. the land between 2 block mountains is called rift valley.

F. Picture study

Look at the photographs of a plain and a plateau given here and answer the questions.

Question 1.
How does a plain look different from a plateau ?
Answer:
A plain is a flat piece of land where it is very easy to build houses, roads and carry agricultural practices whereas a plateau is a flat raised piece of land with steep slopes and high cliffs from the surrounding land which makes the soil rich in minerals like iron, copper, manganese.

Question 2.
Why are river plains thickly populated ?
Answer:
The river plains are thickly populated as it is easier to make buildings, construct roads and have all kinds of transportation facilities. The land is also very fertile, rich in minerals. Thus, making it easier for people to grow crops for their living.

Question 3.
How is life in the plains different from life in the mountains?
Answer:
Landforms also influence weather. The higher one goes the colder it gets, while down in the plains and valleys it is warmer. Since landforms affect climate they also affect farming. It is more difficult to grow crops and rear cattle on hillsides than it is in the plains. In the plains, it is easier for people to make roads and houses and to dig wells, unlike in the mountains where it is difficult and expensive to make them and water has to be brought from distant streams. In other words, life in the mountains is more difficult than life in the plains.

Selina Concise Physics Class 6 ICSE Solutions – Magnetism

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Selina Concise ICSE Solutions for Class 6 Physics Chapter 6 Magnetism

• Synopsis
• The first natural magnet was discovered in Magnesia, a town in Greece. It was called the lodestone.
• Artificial magnets are made of iron or steel. They are made of different shapes namely the bar magnet, cylinderical magnet, U-shaped magnet, horseshoe magnet, magnetic needle, and compass.
• The materials which are attracted by a magnet are called magnetic materials. Examples: iron, steel, cobalt.
• The materials which are not attracted by a magnet are called non-magnetic materials. Examples: paper, wood, brass, plastic, copper aluminum, etc.
• A magnet has two poles, a north, and a south pole.
• A magnet has the following properties:

1. A magnet attracts small pieces of iron.
2. A magnet always rests in the north-south direction, if it is free to swing.
3. Like poles repel each other and unlike poles attract each other.
4. Poles always exist in pairs, cannot be isolated.

• Magnets are used to separate iron and steel from their mixture with non-magnetic substances. –
• Magnets are used in many electrical appliances such as an electric bells, loud-speaker, etc.
• A magnetic compass is used by sailors and navigators to find the north-south direction.
• Magnetic induction is the process in which a piece of iron temporarily behaves like a magnet in the presence of another magnet.
• When a magnet is placed near an iron piece, the iron piece behaves like a magnet. The end of the iron piece near the north pole of the magnet becomes a south pole while the farther end becomes a north pole.
• It is because of magnetic induction that a magnet attracts a piece of iron.
• An iron piece can be made into a magnet by any of the following methods:

1. Magnetic induction
2. Single touch method
3. Double touch method
4. Electrical method

• In the single touch method, we need a single magnet, but in the double touch method we need two magnets, hi these methods, the end touched last by the magnet has the polarity opposite to that of the striking pole.
• Powerful magnets are made by the electrical method.
• Electromagnets or temporary magnets are made of soft iron.
• Permanent magnets are made of steel.
• Electromagnets are used in devices like electric bell, magnetic toys, telephone etc.
• Permanent magnets are used in devices like galvanometer, ammeter, voltmeter etc.
• A magnet can be destroyed by rough handling, by dropping it several tunes, by hammering it repeatedly and by heating it.
• The magnetic field around a magnet is the space in which a magnetic substance such as small iron piece experiences a force of attraction.
• The earth itself behaves like a magnet. It has its own magnetic field.
• The south polarity of the earth is near the geographic north pole and the north polarity of the earth is near the geographic south pole.
• Magnetic keepers are used to store the magnets.
• Magnetic keepers are small pieces of soft iron.

ACTIVITY 1

Magnetic objects
Iron, Steel, Cobalt, Nickel
Non-magnetic objects
Wood, Stone Plastic, Rubber Copper, Sand, Gold, Silver, Brass Paper, Aluminium

Test yourself

A. Objective Questions

1. Write true or false for each statement.

(a) Artificial magnets are weaker than the natural magnets.
Answer. False
Artificial magnets are stronger than the natural magnets.

(b) Poles of a magnet cannot be separated.
Answer. True

(c) A magnet can attract only a magnetic substance.
Answer. True

(d) A magnet has no effect when it is heated to a high temperature.
Answer. False.
A magnet get demagnetised when it is heated to a very high temperature.

(e) Permanent magnets get easily demagnetised.
Answer. False.
Permanent magnets cannot be demagnetised.

(f) Magnetic poles occur in pairs.
Answer. True

(g) Single touch method is better than the electrical method for making a magnet.
Answer. False.
Electrical method is better than single touch method.

(h) Magnetic keeper is a wooden piece.
Answer. False.
Magnetic keepers are the pieces of soft iron.

(i) Copper cannot be magnetised.
Answer. True

2. Fill in the blanks

(a) Temporary magnets are usually made up of soft iron.
(b) Rough handling destroys the magnetic properties of a magnet.
(c) Like poles repel each other.
(d) A freely suspended magnet points in the north-south direction.
(e) In a magnet, ends have the maximum attractive property.
(f) A magnet has two poles.

3. Match the following

4. Select the correct answer

(a) If we suspend a magnet freely, it will settle in .

1. east-west direction
2. north-south direction
3. north-east direction
4. east-south direction

(b) Making a magnetic substance a magnet by bringing it closer to another magnet without touching it, is

1. magnetic induction method
2. single touch method
3. double touch method
4. electrical method

(c) An example of natural magnet is

1. iron
2. steel
3. lodestone
4. none of above

(d) The artificial magnet used to detect direction in the laboratory is

1. U-shaped magnet
2. horse shoe magnet
3. electromagnet
4. magnetic compass

B. Short/Long Answer Questions

Question 1.
What is a magnet ?
Answer:
The substances which have the property of attracting iron, are called magnets.

Question 2.
What are magnetic and non-magnetic substances ? Give two examples of each.
Answer:
Magnetic substances: The substances that get attracted by a magnet are called magnetic substances. Iron, steel, cobalt and nickel are magnetic substance
Non-magnetic substances : The substances that do not get attracted by a magnet are called non-magnetic substances, e.g., wood, plastic, copper, paper, aluminium, rubber, stone.

Question 3.
What are natural and artificial -magnets ?
Answer:
Natural magnets: Natural magnets are those which are found in nature e.g. load stone.
Artificial magnets: Man made magnets are called artificial magnets, e.g. electromagnet.

Question 4.
How is an artificial magnet prepared from a natural magnet ?
Answer:
Pieces of iron or other materials are made magnets by rubbing them with natural magnets (or by passing direct current through a wire wound around them). This is how artificial magnets are made.

Question 5.
State two ways of magnetising an iron piece.
Answer:
The two ways of magnetising an iron piece are:

1. Magnetic induction method.
   Take a long iron nail and test it for magnetic properties by bringing near the magnetic substances. You will see nail does not attract the magnetic substances. Now bring near a pole of a bar magnet to the head of the nail. Now bring the iron paper clips near the pointed end of the nail, you will observe that the iron paper clips now get attracted towards the nail. This is because iron nail has become magnet. Now take the bar magnet away form the iron nail, paper clips fall off. This magnetism is temporary.
   
2. Single touch method: Take a demagnetised piece of iron. Place it on a table surface. Take a magnet and select its one pole. Now mb it with the selected pole on the iron in one direction for several times. After sometime, the iron piece turns into a magnet.
   

Question 6.
How can magnetic properties of a magnet be destroyed ?
Answer:

1. By hammering the magnet repeatedly.
2. By rough handling
3. By heating.

Question 7.
Why docs a freely suspended magnet always rest in north- south direction ?
Answer:
A freely suspended magnet always rest in north-south direction because the north-pole of the magnet lies in the geographic north direction and the south pole of the magnet lies in the geographic south direction. So it aligns itself in N-S direction. As unlike poles attract and like poles repel.

Question 8.
Draw diagrams of the artificial magnets of four different shapes.
Answer:

Question 9.
Why are the artificial magnets preferred over the natural magnets ?
Answer:
Artificial magnets are preferred over natural magnets because natural magnets are weak and often irregular in shape, they can readily be magnetised and demagnetised by turning the current on or off in the coil.

Question 10.
Describe an experiment to show that the maximum attractive property is at the poles of a magnet.
Answer:
Take a bar magnet and place a steel pin at some distance. We observe that nothing happens. Now, bring the steel pin near the pole of the bar magnet. We notice that pin sticks to the magnet. This experiment shows that maximum magnetic force acts at the poles of the magnet.

Question 11.
State four important properties of a bar magnet.
Answer:

1. Attractive property: A magnet can attract small pieces of iron filing or other ferromagnetic materials.
2. Directive property: If a magnet is suspended horizontally by a thin thread (say silk thread), it rests always pointing north- south direction of earth.
3. Like poles always repel each other and unlike poles attract each other.
4. Poles always exist in pairs : Single pole can never exist.

Question 12.
Explain the attractive property of a magnet with the help of an experiment.
Answer:
Take iron filling on a piece of paper. Bring a bar magnet near it. Iron filling will cling to it. It shows the attractive property of magnet.

Question 13.
Describe the method by which an iron bar can be made a magnet.
Answer:
Single touch method : Place the iron bar (or the needle) AB on a table. Take a bar magnet NS and place it almost vertical with its north pole (N) on the end A of the bar.
Move the magnet along tire iron bar till the other end B is reached.

Lift the magnet at the end B and again place it on the first end A Again stroke the bar. Repeat the process about 20 times. Then turn the iron bar AB upside down. Again stroke it with the magnet about 20 times. The bar now becomes a magnet.

Question 14.
How are the magnets kept safely ? What is the role of keepers in storing the magnets ?
Answer:
When magnets are not in use they should be kept and stored in magnetic keepers. The magnetic keeper are the pieces of soft iron. A magnetic keeper has a card board with one or two iron soft pieces. Two magnets are placed in such a way that their opposite poles are close to each other and then a soft iron keeper is attached with it.

Question 15.
Define the term magnetic field of a magnet. How will you recognise it experimentally ?
Answer:
The space around a magnet in which if a magnetic substance such as small pieces of iron, are placed, they get attracted to-wards the magnet, is called the magnetic field.
Recognition of the magnetic field around a magnet: If a magnet is placed below a sheet of stiff paper and some iron filings are spread on it, then on tapping the sheet gently, the iron filings are found to arrange themselves in a definite pattern as shown in fig.

Question 16.
How will you make an iron bar electromagnet ? Draw a diagram showing the polarities of the electromagnet.
Answer:
Take the given iron bar AB. Wound several turns of insulated copper wire over the bar. Connect the ends of the wire to a battery through a switch. Press the switch to pass current. After some time, the bar AB becomes a magnet.

The end A of the bar at which the current enters the coil in clock¬wise direction becomes the south pole (S) and the end B of the bar at which the current leaves the coil in anti-clockwise direction becomes the north pole (N).

Question 17.
State two ways of increasing the strength of an electro Magnet
Answer:
Strength of the electromagnet: The strength of the electromagnet can be increased:

1. by increasing the current in the coil, and
2. by increasing the total number of turns of the coil.

Question 18.
Suppose you are given a long bar magnet and you are asked to break it into four small magnets. Draw diagrams showing the polarities of each broken part.
Answer:

Question 19.
State three important uses of a magnet.
Answer:
Use of magnet:

1. Magnets are used in magnetic compass, door bells, refrigerators.
2. Magnets are used in dynamos, motors, loudspeakers, microphones etc.
3. Ceramic magnets are used in computers.
4. Magnets are used in toys to give magic effect.

Question 20.
What is magnetic induction ? Explain with the help of a diagram.
Answer:
Magnetic Induction: The property by which an ordinary piece of iron acquires magnetic properties temporarily due to the pres¬ence of another magnet close to it, is known as magnetic induction
Take a long nail. Put it on the arm of a stand. Spread some iron pins on the base of stand. You will find that the pins do not get attracted towards the nail. Now touch a magnet at the end of nail. As the end is brought close to the head of nail, some pins cling to the nail. It happens because the nail turns into magnet and acquires the properties of magnetism. The moment you remove the magnet from the head of the nail. The pins will fall down. It will no more be a magnet.

Question 21.
In which direction does a suspended bar magnet come to rest? Give reason.
Answer:
A magnet always rests in North and South direction, i.e. N-end always towards North of Earth and S-end towards South of Earth.

Question 22.
State three differences between the temporary and permanent magnets.
Answer:
Temporary magnet

1. It is made up of soft iron.
2. The magnet which loses its magnetism as soon as magnetising force is removed away from it.
3. Because of its weak power, it is not used to make iron piece into magnet.

Permanent magnets

1. It is made up of steel, cobalt and nickel.
2. The magnet, which does not lose its magnetic properties easily is called permanent magnet.
3. It can convert ordinary piece of iron into a temporary magnet.

Question 23.
State three ways of demagnetising a magnet.
Answer:
A magnet can be demagnetized in the following ways 

1. rough handling
2. hammering the magnet several times.
3. passing an alternating current around the magnet.
4. dropping the magnet on the floor several times.
5. heating the magnet to a very high temperature.

Question 24.
Suggest one way to recognise the magnetic field of the earth.
Answer:
If we suspend a magnet such that it is free to swing, we see that it always rests in the north-south direction. The north pole of the magnet lies in the geographic north direction and the south pole of the magnet lies in the geographic south direction. So it aligns itself in N-S direction.

Question 25.
Name the material of core of an electromagnet for

1. temporary magnet
2. permanent magnet.

Answer:

1. They are made of soft iron.
2. They are made of iron, steel, cobalt, nickel or an alloy called ANILCO.

Question 26.
You are given an iron nail, a torch cell and a long piece of insulated copper wire. With the help of a labelled neat diagram, describe in steps how you will make the nail, an electromagnet.
Answer:
Aim : To make an electromagnet.
Materials Required : An iron nail, a battery, a switch, some insulated copper wire and some iron paper pins.
Procedure : Coil the insulated copper wire around the iron nail. Connect the ends of the wire to the battery through the switch. Close the switch so that electric current flows through the copper wire. Now bring the iron paper pins close to the iron nail.
Observation And Conclusion : The paper pins get attracted to the nail, showing that the nail has turned into an electromagnet. Now, if you switch off the current, the iron paper pins will drop off the iron nail.

Question 27.
Describe an experiment to illustrate that like poles repel while the unlike poles attract.
Answer:

1. Take two bar magnets A and B. Suspend one magnet A with a silk thread from a support so that it is free to swing. The magnet will come to rest in the north-south direction. The north pole of the magnet is in the north direction and the south pole of the magnet is in the south direction.
2. Now holding the other magnet B in your hand, bring its north pole near the north pole of the suspended magnet A (such that the two magnets do not touch each other) as shown in figure. You will observe that the suspended magnet A moves away from the magnet B. This shows that the like poles repel each other.
   

Now bring the south pole of the magnet B near the north pole of the suspended magnet A as shown in figure, without touching it. You will observe that the magnet A moves towards the magnet B. This shows that the unlike poles attract each other.

Question 28.
What are magnetic keepers ? Name its material.
Answer:
Magnetic keepers are used to store the magnets. Magnetic keepers are small pieces .of soft iron.

Question 29.
How are the north and south poles of a magnet located ? Explain.
Answer:
Suspend a bar magnet with a silk thread from a wooden stand as shown in figure. The magnet swings for some time and then eventually comes to rest in a particular direction i.e., north-south direction. If we disturb the magnet a little, the magnet again comes to rest in the north-south direction.

The end of the magnet which points towards the north is called the north seeking pole or simply the north pole and the end which points towards the south is called the south seeking pole or simply the south pole. The north and south poles are marked by the letters N and S respectively.

 

Selina Concise Chemistry Class 6 ICSE Solutions – Pure Substances and Mixtures ; Separation of Mixtures

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Chemistry for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Chemistry Chapter 5 Pure Substances and Mixtures ; Separation of Mixtures

POINTS TO REMEMBER

1. Element is made up of atoms of the same kind i.e. atoms of gold are similar in every respect i.e. have same melting point and same boiling pts. same colour, mass and odour.
2. Molecules of a compound are similar in every respect i.e. same composition taste, colour and odour i.e. compound water is made up of similar molecules.
3. Pure substances are either elements or compounds have definite set of properties.
4. Pure substances are required to maintain good health of human beings. Chemists, technologists and scientists need pure substances for manufacture of medicines, chemicals in industry and for scientific purposes.
5. Milk, air, bronze, sugar and water solution, salt and water solution, salt, iron filings and sand, petrol are all mixtures.
6. Mixtures, two or more components mixed in any ratio, undergo ho chemical change and retain their individual properties, can be separated by simple physical methods.
7. Mixture has no formula, no change in volume, no change in mass, energy is neither needed nor produced.
8. Mixture is impure substance.
9. Homogeneous mixture : in which constituents are uniformaly distributed throughout its volume, e.g. salt and water solution.
10. Heterogeneous mixture: The components are not uniformly distributed through its volume and components can be easily seen separately, e.g. water, oil solution.
11. Milk is emulsion but this mixture cannot be separated. Oh shaking a mixture of mustard oil and water vigorously mixture becomes milky and is called an emulsion after some time water and oil get separated.
12. Alloys are homogeneous mixtures of metal with metals or metal with non-metals.
13. Salt and sand can be seperated by solvent extraction method where one of the solid component (salt) is soluble in liquid.
14. Coagulation or loading : When alum (a chemical) is added to mixture dissolves in water and form clusters with clay and fine dust particles making them heavier, increases the rate of sedimentation.
15. Centrifugation method is used to separate solids from liquids where mixture is homogeneous. Cream is separated being lighter on churning floats on a liquid (milk).
16. Loading : The process of adding a chemical substance to help the suspended solid particles in liquid to form a sediment is called loading.

EXERCISE – I

Question 1.
Select homogeneous and heterogeneous mixtures from the following:
Salt solution, petrol and water, sand and charcoal, alcohol and water, air dissolved in water, air, sea water, fruit juices, mist, brass.
Answer:
Homogeneous mixture : Salt solution, alcohol and water, air dissolved in water, sea water, brass.
Heterogeneous mixture: Sand and charcoal, air, fruit juice, mist, petrol and water.

Question 2.
Define the following :

(a) Pure substance
(b) Impure substance
(c) Alloy
(d) Solution
(e) Heterogeneous mixture
(f) Homogeneous mixture

Answer:

(a) Pure substance : “Pure Substance is either element or compound. It contains the same kind of atom or molecules and has a definite set of physical and chemical properties.”
(b) Impure substance : “A substance in which some other substances are also present in smaller or larger amounts is called an impure substance. Mixtures are impure substance.
Example of impure substance is air.
(c) Alloy : “A homogeneous solid mixture of two or more metals or a metal and a non-metal is called an alloy.”
(d) Solution : “The homogeneous mixture of water (or any other solvent) and a substance soluble in it is called a solution.”
(e) Heterogeneous mixture : “A mixture in which the components are not uniformally distributed through its volume and can be easily seen separately is called heterogeneous mixture.”
(f) Homogeneous mixture : “A mixture in which its constituents are uniformly distributed throughout its volume and cannot be seen separately is called a homogenous mixture.”

Question 3.
List four characteristics of a mixture.
Answer:
Four characteristics of a mixture :

1. Mixture has no fixed composition.
2. To form a mixture energy is neither produced nor evolved.
3. Mixture has no fixed melting’point and boiling points.
4. Mixture retain the properties of its components.
5. Components of mixtures can be seperated by simple physical methods.

Question 4.
Give reasons :

(a) Why do sugar and water retain their individual properties in a sugar solution ?
(b) Why do petrol and water form a heterogeneous mixture ?
(c) Why sulphur does dissolve when carbon disulphide is added to a mixture of iron and sulphur but not when it is added to iron sulphide ?

Answer:

(a) As sugar solution is a mixture and mixtures has not any specific set of properties. They show the properties of the individual components from which they are formed.
(b) Petrol and water forms a heterogeneous mixture as its constituents can be seen separately and are not uniformly distributed throughout its volume.
(c) Sulphur has the property to dissolve in carbon disulphide whereas iron does not dissolve and retains its individual property. However, On heating Iron and Sulphur, they chemically combined forming Iron Sulphide. In this, Iron and Sulphur particles do not exists separately as such they loose their individual property.

Question 5.
Give two examples for each of the following types of mixture.

(a) solid-solid
(b) solid-liquid
(c) liquid-gas
(d) gas-gas

Answer:
Two examples of :
(a) solid – solid –

1. sand and sugar
2. sand and iron filling.

(b) solid – liquid –

1. salt and water
2. charcoal and water.

(c) liquid – gas –

1. coca cola
2. mist.

(d) gas – gas –

1. air
2. helium and hydrogen in air balloon,
3. perfumes and air.

Question 6.
Name the components present in the following mixtures:

(a) Brass
(b) Duralumin
(c) Tap water
(d) Bronze
(e) Crude petroleum oil .

Answer:

(a) Brass → Copper and Zinc.
(b) Duralumin → Aluminium + Copper with little manganese and magnesium.
(c) Tap water → air, dissolved salts.
(d) Bronze → Copper, Tin and zinc.
(e) Crude petroleum oil → petrol, kerosene, diesel, LPG, mixed with salt, water and earth particles.

Question 7.
State:

(a) Three differences between water and air.
(b) Four differences between compounds and mixtures.

Answer:
(a)
Water :

1. The components of water are hydrogen and oxygen which are chemically combined in a fixed ratio of 1 : 8 by mass.
2. The chemical composition of water remains same from whatever source it is obtained.
3. The properties of water are completely different from the properties of elements from which it is formed i.e. hydrogen and oxygen.
4. Energy change occurs in the formation of water.
5. A molecule of water is represented by a definite formula H₂O.

Air :

1. The main components of air are nitrogen, oxygen, carbon -dioxide, water vapour which are not chemically combined.
2. The composition of air varies from place to place. During rainy season the air becomes humid due to presence of more water vapour. Some impurities like sulphur dioxide, hydrogen sulphide etc. also changes its composition at some places.
3. The components of air retain their individual properties but not air.
4. No energy change occurs when components of air are mixed together.
5. Air cannot be represented by any chemical formula.

(b)
Compound :

1. A compound is a pure substance.
2. Compounds are always homogeneous.
3. A compound has a fixed composition, i.e., it is formed when two or more pure substances chemically combine in a definite ratio by mass.
4. Formation of a compound involves change in energy.
5. Compounds have specific set of properties.
6. Components of compounds can be separated only by complex chemical processes.

Mixture :

1. A mixture is an impure substance.
2. Mixtures may be homogeneous or heterogeneous.
3. A mixture has no fixed composition, i.e., it is formed by mixing two or more substances in any ratio without any chemical reaction.
4. Formation of a mixture does not involve any change in energy.
5. Mixtures do not have any specific set of properties.
6. Components of mixtures can be separated by simple physical methods.

EXERCISE – II

Question 1.
Define:

(a) Filtration
(b) Sublimation
(c) Evaporation
(d) Crystallisation
(e) Miscible liquids
(f) Immiscible liquids

Answer:

(a) Filtration : The process of separating solid particles from liquid by allowing it to pass through a filter paper is called filtration.
(b) Sublimation : The process in which a solid changes directly into its vapours on heating is called sublimation.
(c) Evaporation : Is the process of converting a liquid into its vapours state either by exposing it to air or by heating.
(d) Crystallisation : Evaporation of liquid from a homogeneous liquit-solid mixture and collecting solid in the form of crystals is called
crystallisation.
(e) Miscible liquids: Homogeneous liquid-liquid mixtures are called miscible liquids.
(f) Immiscible liquids : Heterogeneous liquid-liquid mixtures are called immiscible liquids.

Question 2.
Why do we need pure substances?
Answer:
We need pure substances because of the following reasons:

1. A pure substance has a fixed melting and fixed boiling point.
2. A pure substance has its characteristic taste, colour and odour.
3. Pure substances can not be broken further into more simple substances by any physical means.

Question 3.
Give one example for each of the following types of mixtures.

(a) Solid-solid heterogeneous mixture
(b) Solid-liquid heterogenous mixture
(c) Solid-liquid homogeneous mixture

Answer:

(a) Iron and sulphur.
(b) Sand and water, rice and water.
(c) Sugar from its solution in water.

Question 4.
Name the process by which the components of following mixtures can be separated.

(a) Powdered glass and sugar
(b) Chalk powder and iron filings
(c) Chaff and grain
(d) Salt and water
(e) Wheat and sugar
(f) Sand and camphor
(g) Sugar and water

Answer:

(a) FILTRATION : Glass and sugar on dissolving in water and filtering, glass separates out as residue on the filter paper. Filtrate of sugar solution is heated to remove water by evaporation, sugar is collected as crystals.
(b) MAGNETIC SEPERATION : With the help of a magnet, iron filings can be separated leaving behind chalk powder.
(c) WINNOWING : It separates chaff (lighter) from heavier grains in two different heaps.
(d) EVAPORATION : This method is used to separate the components of a homogeneous solid-liquid mixture, like salt from sea water. Sea water is collected in shallow beds and allowed to evaporate in the sun. When all the water is evaporated, salt is left behind.
(e) EVAPORATION : Wheat and sugar are put in water in a beaker. Sugar dissolves and mixture is passed through strainer and separated and dried. Sugar is obtained by evaporating sugar solution.
(f) SUBLIMATION : Camphor sublimes on heating leaving behind sand.
(g) CRYSTALLISATION : Pure sugar is obtained from its solution in water by the process of crystallisation. At first the sugar solution is heated to evaporate Water at a faster speed. When very less of water is left the solution is cooled. On cooling sugar dissolved in it starts separating out in the form of crystals.

Question 5.
Name:

(a) two substances which can sublime
(b) two substances soluble in water
(c) two substances insoluble in water
(d) four substances that can be used as filters.

Answer:

(a) Camphor and Naphthalene
(b) Sugar and salt (NaCl)
(c) Sand and chalk powder.
(d) (i) Filter paper, (ii) A bead of sand, (iii) Charcoal, (iv) A piece of muslin cloth.

Question 6.
Give reasons :

(a) Sand and saw dust cannot be separated by hand picking.
(b) Magnet is used to separate a mixture of iron and sulphur.
(c) Alum is used in purification of river water.

Answer:

(a) Because in hand picking method substances should be large enough in size to be recognized and picked out by hand but sand and saw dust particles are very small in size so they can’t be picked by hand. It can be separated by filtration.
(b) Mixtures of iron and sulphur can be separated by moving a magnet over them. Iron gets attached to the magnet is separated.
(c) Water from a river, pond or lake contains very fine clay particles. To make them settle at a faster rate, a chemical substance called alum in powdered form is added to such mixtures. It dissolves in water and forms clusters with clay and dust particles making them heavier and increasing the rate of sedimentation.

OBJECTIVE TYPE QUESTIONS

1. Fill in the blanks

(a) The substances that make a mixture are called its constituents or components.
(b) Evaporation or crystallisation is a process to separate solids dissolved in liquids.
(c) Mist is a heterogeneous (liquid in gas) mixture of droplets of water and air.
(d) Clay is separated from water by the method of loading and decantation.
(e) When cereals are washed before cooking, water is separated from the cereals by decantation.
(f) Crystallisation is a process to obtain a very pure form of a solid dissolved in a liquid.
(g) Ammonium chloride can be separated from common salt by the method of sublimation.
(h) The solid particles which remain on the filter paper are called residue and the liquid which passes through it is called filtrate.
(i) The process of transferring the clear liquid layer above the solid particles which settle at the bottom of the container is known as decantation.
(j) Filtration is a method used for the separation of an insoluble solid from a solid-liquid mixture.

2. Write “true” or “false” for the following statements 

(a) A pure substance consists of only one kind of atom or molecule.
Answer. True

(b) Common salt is separated from its solution in water by decantation.
Answer. False
Correct : Common salt is separated from its solution in water by evaporation.

(c) Winnowing is a process to remove small stones from grains.
Answer. False
Correct : Winnowing is a process to remove husk from grains.

(d) Jewellery gold is a homogeneous mixture of metals.
Answer. False
Correct : Jewellery gold is a heterogeneous mixture of metals.

(e) Air can be separated from water by filtration.
Answer. False
Correct : Air can be separated from water by heating.

(f) Salt and air dissolved in water add taste to water.
Answer. True

(g) Steel is an alloy of iron and aluminium.
Answer. False
Correct: Steel is an alloy of iron and carbon.

MULTIPLE CHOICE QUESTIONS

Tick (√) the correct alternative from the choice given for the following statements:

1. The process of adding a chemical substance to help the suspended solid particles to deposit as sediment fastly is called

1. loading
2. sedimentation
3. decantation
4. filtration

2. Salt is separated from sea water by

1. evaporation
2. sublimation
3. crystallisation
4. filtration

3. A mixture of mustard oil and water forms

1. a compound
2. a homogeneous mixture
3. an alloy
4. a heterogeneous mixture

4. A heterogeneous mixture is

1. made up of only one kind of atom
2. made up of only one kind of molecule
3. made up of different kinds of atoms and molecules.
4. that looks uniform

5. Example of a homogeneous mixture is

1. distilled water
2. tap water
3. sand and water
4. sawdust and water

6. A set of mixture is

1. gold, common salt, water, alloy
2. alloy, ink, honey, icecream
3. alloy, mercury, air, sea water
4. milk, duralumin, brass, silver

7. A gas dissolved in a liquid can be separated by :

1. filtration
2. boiling
3. using magnet
4. by crystallisation

8. Copper is not a part of the alloy :

1. brass
2. bronze
3. steel
4. duralumin

9. Which is not a mixture?

1. sugar solution
2. tap water
3. milk
4. distilled water

10. Give one word name for the following

(a) The solid which is left on the filter paper after filtration residue.
(b) The solid particles which separate out from the solution on slow evaporation crystals.
(c) The solid particles that settles at the bottom of the beaker in a heterogeneous mixture of a solid and a liquid decantation.
(d) The clean liquid which is poured out after sedimentation supernatant liquid.
(e) The technique used to separate the light particles from heavy particles using the flow of wind winnowing.

Selina Concise Chemistry Class 6 ICSE Solutions – Air and Atmosphere

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APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 6 Chemistry. You can download the Selina Concise Chemistry ICSE Solutions for Class 6 with Free PDF download option. Selina Publishers Concise Chemistry for Class 6 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

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Selina Concise ICSE Solutions for Class 6 Chemistry Chapter 6 Air and Atmosphere

POINTS TO REMEMBER

1. Air cannot be seen as it is transparent we only feel its presence when it blows.
2. The thick layer of air around earth upto 320 km above the surface is called atmosphere.
3. Air is a mixture of various gases, water vapours, which protects us from harmful rays of Sun. It consists of nearly 80% nitrogen, 20% oxygen.
4. The components of air can be separated by simple physical means. Has no formula.
5. N₂ is inert gas, reduces the effect of O₂ present in air, N₂ is helpful in plant growth as it provides nitrates used by plant for formation of protein which is important nutrient for animals.
6. Oxygen is supporter of combustion no burning is possible without O₂ and no life is possible without it.
7. CO₂ is must for plant life, plants prepare their food taking CO₂ from air. CO₂ maintains temp, of earth and without CO₂ our planet would be too cold.
8. Ozone in the upper layers of atmosphere protects the earth from harmful ultraviolet rays of Sun.
9. Air is useful in many ways : Acts as medium for propagation of sound, birds, insects to fly in air, air ships, aeroplanes to fly only must due to presence of air. Air helps in movement of yachts, parachutes, aircrafts etc. Air is must for animals and plants on earth and air dissolved in water for aquatic life.
10. Respiration : Is a slow chemical process when O₂ present in the inhaled air reacts with the digested food material in the body to release energy, CO₂ and water. Sugar + Oxygen -> Carbon dioxide + Water + Energy.
    Breathing : The complete process in which air is inhaled and exhaled is called breathing.
11. Combustion : Burning of substance in air completely producing CO₂, heat and light.
12. Photosynthesis : Preparation of food by green plants taking CO₂ from air, water from soil in presence of sun light.
13. Oxygen in air remains constant it is not depleted as plants during day time produce lot of O₂ in air.
14. Soil contains air trapped in between its particle and organisms living there breath this oxygen. Due to this earth worms come out of soil during heavy rains as water gets into the pores in the soil.
15. Common pollutant of air are smoke, dust, coal, emitted by industries and automobiles.
16. Gases like SO₂, NO₂ also pollute air as they form corresponding acids when they come in contact with water vapours in air and fall down in the form of acid rain with rain water.
17. These pollutants reduce the visibility which lead to accidents, cause global warming.

EXERCISE-I

Question 1.
What is atmosphere ?
Answer:
The earth is surrounded by a thick layer of air called the atmosphere that extends upto a height of about 320 kilometres above the surface of the earth.

Question 2.
Why can’t we see air ?
Answer:
We can’t see air because it is colourless, odourless and transparent gaseous matter.

Question 3.
What is wind ?
Answer:
Fast moving air is called wind.

Question 4.
What would have happened if there would have been no atmosphere around the earth ?
Answer:
Without atmosphere life would not be possible as atmosphere protects us from harmful gases. We could not live without
air present in atmosphere. In absence of the atmopshere, the earth would get so cold at night that we would not be able to survive. No CO₂ and N₂ for plants without atmosphere.
P.Q. When water is heated, we see bubbles rising up. Why ?
Answer:
Water has a lot of air dissolved on it. This is what allows breathing to fishes and other aquatic beings. The solubility of gases decreases when the temperature is raised, and that is why the dissolved air bubbles out from the water.

Question 5.
Why is air called a mixture ? Give five facts in support of your answer.
Answer:
Air is a mixture because :

1. Air has no formula, a mixture has no formula whereas compound has a formula.
2. No energy changes are involved to form air from various gases.
3. When air is formed out of its constituents no change in mass and no change in volume takes place.
4. Properties of air vary from place to place and time to time. i.e. there is more CO₂ in towns as compared to villages where more oxygen prevails as compared to towns.
5. Components of air can be separated by simple physical methods.

Question 6.
What are the main components of air ? Write down the composition of three main gases present in air by volume.
Answer:
Main components of air are :

Question 7.
What do you observe when

(a) Ice cold water is filled in a glass tumbler.
(b) A burning candle is covered with an inverted jar.
(c) Carbon dioxide gas is passed through lime water.
(d) A beam of light is allowed to enter in a closed dark room through a small hole.

Answer:

(a) We will observe that fine water droplets get deposited on the outer wall of the glass tumbler.
(b) The candle burn more brightly because candle gets oxygen support in burning.
(c) When CO₂ gas is passed through lime water it forms calcium carbonate which is white precipitate (turbidity). This gives the milky white appearance to the solution.
(d) We will observe randomly moving dust particles in the beam of light. This confirms the presence of dust particles in the air.

Question 8.
Write the chemical name of –

(a) Lime water
(b) The white insoluble solid formed on reaction of carbon dioxide with lime water.

Answer:

(a) Calcium hydroxide Ca(OH)₂
(b) Calcium carbonate – CaCO₃

These droplets were present in air as moisture which got condensed on the cooler walls of glass tumbler. This shows the presence of water vapours in air.

EXERCISE-II

Question 1.
Name two important processes supported by oxygen present in air.
Answer:
Two processes supported by oxygen present in air are :

1. Combustion
2. Respiration

Question 2.
Give two uses of the following components present in air:

(a) oxygen
(b) nitrogen
(c) carbon dioxide
(d) water vapour

Answer:

(a) Oxygen: For respiration and breathing no life is possible without oxygen.
Oxygen is the most vital component which is responsible for two most important processes,
(i) Respiration and
(ii) Combustion.
(b) Nitrogen : Present in air gets fixed up in the soil as nitrates used by plants for their growth and for the formation of protein an important nutrient for animals. It is used to make fertilizers and various nitrogenous products.
(c) Carbon dioxide : Carbon dioxide is used by plants to prepare their food by photosynthesis. Dry ice (solid carbon-dioxide) is used as a refrigerant. Carbon dioxide is used to prepare fizzy drinks like soda water.
(d) Water vapour : Water vapors present in air provide moisture for both plants and animals. It also helps in predicting climatic conditions of a particular area as its amount varies from place to place and time to time.

Question 3.
Define the following:

(a) Respiration
(b) Photosynthesis
(c) Combustion.

Answer:

(a) Respiration : Respiration is a chemical process that takes place in all living beings (slow in plants). In this process, oxygen present in inhaled air reacts with the digested food material in the body. This results in release of energy, carbon-dioxide and water.
Sugar + Oxygen → CO₂ + Water + Energy.
(b) Photosynthesis : Process of producing food by green plants taking CO₂ from air, water from soil by roots and in presence of sun light and chlorophyll is called photosynthesis.
(c) Combustion : Combustion also called burning “is burning of substance in oxygen of air completely producing heat and light is called combustion.”

Question 4.
What are fuels ? Give two examples of modern fuels.
Answer:
Fuels : The substances which burn in air to produce large amount of energy in the form of heat and light are called fuels.
Examples :

1. CNG (Compressed natural gas)
2. LPG (Liquefied natural gas)

Question 5.
Give reasons :

(a) Aquatic animals and plants are able to survive in matter.
(b) A burning candle stops burning if covered with a glass tumbler.
(c) Mountaineers and divers carry oxygen cylinders with them.
(d) When water is heated, we see bubbles rising up.

Answer:

(a) Aquatic animals and plants use oxygen dissolved in water and survive.
(b) Oxygen is necessary for combustion when covered with a glass tumbler supply of oxygen stops.
(c) For artificial respiration mountaineers carry oxygen cylinders as at high altitudes, the air is thin and breathing becomes difficult. Also divers carry oxygen cylinder for artificial respiration as there is less oxygen dissolved in water (less dense) and breathing becomes difficult.
(d) These bubbles come from the air dissolved in water. The marine life uses air dissolved in water.

Question 6.
Name the processes which maintain the balance between oxygen and carbon dioxide in the air. How is it done?
Answer:
Respiration and combustion are the processes which maintain the balance between oxygen and CO₂ in the air.

1. Respiration : Respiration is a chemical process that takes place in all living beings. In this process, oxygen present in the inhaled air reacts with the digested food material in the body. This results in the release of energy, carbon dioxide and water.
2. Combustion : Burning or combustion is a process in which a substance reacts chemically with oxygen and gets oxidised, with the release of energy in the form of heat and light. It is a fast process. During the process of burning, along with energy, carbon dioxide and water vapour are also produced.

Question 7.
State two similarities and two differences between respiration and burning.
Answer:
Similarities:
Burning

1. Oxygen is needed to combine with carbon and hydrogen in compound.
2. CO₂ and H₂O are formed with release of energy.

Respiration

1. Oxygen is needed tocombine with C and H2 of food.
2. CO₂ and H₂O are formed with release of energy.

Differences :
Burning

1. It occurs at higher temperature.
2. Is fast process.
3. A natural and continous process.

Respiration

1. It occurs at body temperature.
2. Is slow process.
3. An artificial & discont inuous process.

Question 8.
Define rusting ? What are the two necessary conditions for rusting of iron. Give the chemical name of rust.
Answer:
Rusting : Slow conversion of iron into its hydrated oxide in the presence of moisture and air is called rusting.
Conditions for rusting:

1. Presence of moisture (water).
2. Presence of oxygen (air).

Chemical name of rust is hydrated iron oxide [Fe20rxH20]

Question 9.
How is air useful to :

(a) water boats
(b) agriculture
(c) windmills
(d) scooters and cars.

Answer:

(a) Air helps movement of water boats.
(b) Air speeds up drying up of agricultural products like grains, pulses fruits etc. Air helps in pollination of flowers and dispersel of seeds.
(c) Windmills work where there is sufficient movement of air.
(d) Air filled tyres of cars move smoothly on road as there is less friction.

Question 10.
State the full form of LPG and CNG ? How are the two different in their composition ?
Answer:
LPG (Liquefied Petroleum Gas): It is obtained from crude petroleum oil. It mainly contains gaseous compounds known as isobutane and butane. Popularly it is known as cooking gas. It is the best fuel for domestic purposes and in laboratories. It is available in cylinders. It is also supplied through pipes in big cities.
CNG (Compressed Natural Gas): It is produced along with crude oil. It mainly contains methane gas. It has become a popular fuel for vehicles like three wheeler scooters, cars and buses. It is a cheap fuel as well as pollution free. It is used as a substitute of petrol.
Difference in composition
LPG is obtained from crude petroleum oil. It mainly contains gaseous compounds known as isobutane and butane. While
CNG is produced along with crude oil. It mainly contains methane gas.

Question 11.

(a) Why is nitrogen important to all living beings ?
(b) What is nitrogen fixation ?

Answer:

(a) Nitrogen constitutes 78% of air by volume. It is of vital importance to the plants, animals and human beings as it is needed to prepare vital nutrient ‘protein’ to every living being which is necessary for their growth.
(b) Nitrogen cannot be absorbed directly by plants. It is first fixed up in the soil as nitrites and nitrates and then absorbed by the plants in soluble forms. This phenomenon is called nitrogen fixation.

EXERCISE-III

Question 1.
What is air pollution ?
Answer:
Air Pollution : “Mixing of UNWANTED and HARMFUL SUBSTANCES in air is called AIR POLLUTION.”

Question 2.
Mention five causes of air pollution.
Answer:
CAUSES OF AIR POLLUTION ARE:

1. Burning of FOSSIL FUELS and FIBRES.
2. Cutting of forests.
3. Erruption of volcanoes.
4. Increase in POPULATION.
5. Agricultural activities like use of chemical fertilisers, insecticides, pesticides and burning of husks etc.

Question 3.
Name two air pollutants which

(a) affect our health
(b) cause acid rain
(c) cause global warming.

Answer:

(a) Two air pollutants that affect our health are :

1. DUST
2. SMOKE

(b) Two air pollutants that cause acid rain are :

1. SULPHUR DIOXIDE (SO₂) and
2. NITROGEN DIOXIDE (NO₂)

(c) Two air pollutants that cause global warming are :

1. CARBON DIOXIDE (CO₂)
2. METHANE (CH₄)

Question 4.
What is meant by ozone depletion?
Answer:
Ozone is present in the upper layer of atomosphere called stratosphere. It protects the earth from harmful ultraviolet rays of the sun.
Some air pollutants like chlorofluorocarbon (CFC) react with ozone present in the atmosphere. These pollutants reduce the density of the air. The ultra-violet rays from the sun reach directly on the earth which affect human health, causing skin diseases and cancer and also increase the earth’s temperature.

Question 5.
State four steps to be taken to control air pollution.
Answer:
Four steps taken to control air pollution :

1. Tall chimneys be installed in factories and power houses so that smoke and gases rise high and get diluted.
2. GROW more tall trees to absorb CO₂ Also plants help in bringing rains.
3. Use unleaded petrol and CNG in all public transport vehicles
4. Industries should be located far away from residential areas.

Question 6.
Name three greenhouse gases.
Answer:
Carbon dioxide, methane, nitrous oxide, etc.

OBJECTIVE TYPE QUESTIONS

1. Fill in the blanks

(a) The layer of air around the earth is called the atmosphere.
(b) Although we cannot see air, we can feel it.
(c) Air is a mixture of gases.
(d) Plants and animals maintain the balance of carbon- dioxide and oxygen in air.
(e) Polluted air is harmful for health.
(f) The supporter of combustion in air is oxygen.
(g) Green plants need CO₂ water and light to prepare food.
(h) Oxygen is used in burning the food to get energy.
(i) Aquatic plants and animals use dissolved oxygen in water.
(j) The reddish brown powder on the surface of iron nails exposed to air and moisture is called rust.

2. Write ‘true’ or ‘false for the following

(a) Air is a compound.
Answer. False
Correct: Air is a mixture.

(b) Carbon dioxide is given out during photosynthesis.
Answer. False
Correct : Oxygen is given out during photosynthesis.

(c) Respiration needs nitrogen.
Answer. False
Correct: Respiration needs oxygen.

(d) The composition of air was discovered by Lavoisier.
Answer. True

(e) The major component of air is oxygen.
Answer. False
Correct: The major component of air is nitrogen.

MULTIPLE CHOICE QUESTIONS

Tick (√) the correct alternative from the choice given for the following statements

1. Air consists of

1. only oxygen
2. only nitrogen
3. only carbon dioxide
4. all of these

2. Air pollution is due to the

1. cutting of green plants
2. gases like carbon monoxide, sulphur dioxide etc.
3. smoke given out by factories
4. all of the above

3. The gases which cause acid rain are

1. sulphur dioxide and oxygen
2. nitrogen and oxygen
3. carbon dioxide and water vapour
4. nitrogen dioxide and sulphur dioxide

4. Rust is

1. hydrated iron oxide
2. hydrated copper sulphate
3. anhydrous iron oxide
4. none of the above

5. Photosynthesis is a process in which plants

1. take in oxygen and give out carbon dioxide
2. take in carbondioxide and give out oxygen
3. take in nitrogen and give out oxygen .
4. none of the above.

6. Fuels which do not leave any residue on burning are

1. coal and wood
2. coal and LPG
3. wood and CNG
4. LPG and CNG

7. Respiration

1. is a slow process
2. is a natural and continuous process
3. takes place at body temperature
4. all of the above

8. Which of the following is common in combustion and respiration

1. oxygen
2. release of heat and light
3. natural process
4. nitrogen

9. Which of the following is not a green house gas ?

1. carbondioxide
2. sulphur dioxide
3. methane
4. nitrogen

10. The substance which accelerates the speed of a reaction without itself undergoing any change is called

1. catalyst
2. pollutant
3. fuel
4. none of the above.

Selina Concise Physics Class 7 ICSE Solutions – Motion

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 7 Physics. You can download the Selina Concise Physics ICSE Solutions for Class 7 with Free PDF download option. Selina Publishers Concise Physics for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

Selina Class 7 Physics ICSE SolutionsChemistryBiologyMathsGeographyHistory & Civics

Selina Concise ICSE Solutions for Class 7 Physics Chapter 2 Motion

• Points to Remember
•  Motion— Motion is the change in position with respect to a set of stationary landmarks.
•  Types of motion are translatory, rotatory and oscillatory.
•  A body is said to move in a translatory motion if the whole body moves through the same distance in the same interval of time.
•  A body is said to be in rotatory motion if it moves about a fixed point without changing the radius of its motion.
•  A body is said to be in oscillatory motion if it moves to and fro about its mean position.
•  A body is said to be in vibratory motion if the body moves to and fro in a particular style.
•  Oscillation of pendulum is one complete to and fro motion.
•  The maximum displacement on either side of a mean position is called amplitude.
•  A motion which repeats itself at regular intervals of time is called periodic motion.
•  A physical quantity which has only magnitude and no direction is called a scalar quantity.
•  A physical quantity which has magnitude as well as direction is called a vector quantity.
•  Speed is the distance travelled per unit time. It is a scalar quantity.
•  The displacement per unit time is known as the velocity of the body. It is a vector quantity.
•  The rate of change of velocity is called acceleration. It is a vector quantity.
•  Frequency is the number of complete oscillations in one second.
•  Unit of frequency is Hertz.
•  Motion is of two types (a) uniform (b) non-uniform motion.

Test yourself

A. Objective Questions

1. Write true or false for each statement

(a) Two trains going in opposite directions with the same speed are at rest relative to each other.
Answer. False.

(b) A ball is thrown vertically upwards. Its motion is uniform throughout.
Answer. False.

(c) The motion of a train starting from one station and reaching at another station is non-uniform.
Answer. True.

(d) A motion which repeats itself after a fixed interval of time is called periodic motion.
Answer. True.

(e) A ball thrown by a boy from a roof-top has oscillatory motion.
Answer. False.

(f) Mass has both magnitude and direction.
Answer. False.

(g) .Weight always acts vertically downwards.
Answer. True

(h) Mass varies from place to place but weight does not.
Answer. False

2. Fill in the blanks

(a) Two boys cycling on the road with the same speed are at rest relative to each other.
(b) The motion in a straight line is rectilinear motion.
(c) One to and fro motion of a clock pendulum takes time = 2 s
(d) 36 km h^-1 = 10 m s^-1
(e) Total distance travelled = average speed × total time taken.
(f) The weight of a girl is 36 kgf. Her mass will be 36 kg.
(g) The weight of a body is measured using a spring balance.

Activity

3. Match the following

4. Select the correct alternative

(a) A book lying on a table is an example of

1.  a body at rest
2.  a body in motion
3.  a body neither at rest nor in motion
4.  none of these

(b) The motion of a pendulum is

1.  rotatory
2. oscillatory
3.  curvilinear
4.  rectilinear

(c) A car moving on a straight road is an example of

1.  rotatory motion
2.  rectilinear motion
3.  oscillatory motion
4.  periodic motion

(d) A ball falls down vertically. Its motion is

1.  periodic
2.  linear
3.  circular
4.  vibratory

(e) If a body covers equal distance in equal interval of time, the motion is said to be

1.  uniform
2.  non-uniform
3.  oscillatory
4.   rotatory

(f) A boy goes from his house to school by bus at a speed of 20 km h^-1 and returns back through the same route at a speed of 30 km h_1. The average speed of his journey is

1.  24 km h^-1
2.  25 km h^-1
3.  30 km h^-1
4.  20 km h^-1

(g) The earth attracts a body of mass 1 kg with a force of 10 N. The mass of a boy is 50 kg. His weight will be

1.  50 kg
2.  500 N
3.  50 N
4.  5 N

B. Short/Long Answer Questions

Question 1.
Explain the meaning of the terms rest and motion.
Answer:
Rest— A body is said to be at rest if it does not change its position with respect to its immediate surroundings.
Motion— A body is said to be in motion if it changes its position with respect to its immediate surroundings.

Question 2.
Comment on the statement ‘rest and motion are relative terms’. Give an example.
Answer:
Imagine you are sitting inside a moving bus. When you look outside you will observe that you are moving. Now look to the roof of the bus. With respect to the roof of bus, you are at rest. Hence it is concluded that rest and motion are relative terms.

Question 3.
Fill in the blanks using one of the words : at rest, in motion.
(a) A person walking in a compartment of a stationary train is relative to the compartment and is relative to the platform.
(b) A person sitting in a compartment of a moving train is relative to the other person sitting by his side and is relative to the platform.
Answer:
(a) A person walking in a compartment of a stationary train is in motion relative to the compartment and is in motion relative to the platform.
(b) A person sitting in a compartment of a moving train is at rest . relative to the other person sitting by his side and is in motion relative to the platform.

Question 4.
Name five different types of motion you know.
Answer:
The different types of motion are :
1. Translatory motion
2. Rotatory motion
3. Oscillatory motion
4. Vibratory motion
5. Periodic motion
6. Multiple motion
7. Random motion.

Question 5.
What do you mean by translatory motion ? Give one example.
Answer:
If an object like a vehicle, moves in a line in such a way that every point of the object moves through the same distance in the same time, then the motion of the object is called translatory motion.
Example :
The motion of an apple falling from a tree, the motion of a man walking on a road, the motion of a box when pushed from one comer of a room to the other, are all the translatory motion.

Question 6.
Explain the meanings of (i) rectilinear motion, and (ii) curvilinear motion. Give one example of each.
Answer:
(i) Rectilinear motion — If the motion of a body is along a straight line, it is said to be the rectilinear or linear motion. The motion of bullet fired from a gun.
(ii) Curvilinear motion — If the motion of a body is along a curved path, it is said to be the curvilinear motion. For example, the motion of a cycle while taking a turn on the road, a car moving along a curved path, a ball thrown by an athlete are in curvilinear motion.

Question 7.
What is rotatory motion ? Give two examples.
Answer:
Rotatory motion— A body is said to be in a rotatory motion or a circular motion if it moves about a fixed axis without changing the radius of its motion.
Examples : The blades of a fan, a spinning wheel.

Question 8.
What is meant by circular motion ? Give one example.
Answer:
The motion of a body along a circular path is called circular motion.
Example : A girl is whirling a stone tied at the end of a string in a circular path.

Question 9.
How does a rotatory motion differ from the circular motion?
Answer:
(i) In rotatory motion, the axis of rotation passes from a point
in the body itself whereas in circular motion, the axis of revolution passes through a point outside the body. Thus the motion of earth around the sun is the circular motion whereas the motion of earth about its own axis is the rotational motion.
(ii) In the circular and rotatory motions, the distance of a point of a the body from a fixed point always remains same, whereas it is not same in curvilinear motion.

Question 10.
Explain oscillatory motion by giving one example.
Answer:
Oscillatory motion— The to and fro motion of a simple pendulum is an oscillatory motion.
Example : 1. The motion of a swing, 2. Piston of an engine.

Question 11.
What is vibratory motion ? Give one example.
Answer:
In vibratory motion, a part of the body always remains fixed and the rest part moves to and fro about its mean position. During the vibratory motion, the shape and size of the body changes. Example : When we breath, our chest expands and contracts. This motion is vibratory motion.

Question 12.
Differentiate between periodic and non-periodic motions by giving an example of each.
Answer:
Periodic motion : A motion which gets repeated after regular intervals of time is called a periodic motion.
Examples : The earth moving around the sun takes 365 days to complete one revolution and this motion gets repeated after every 365 days.
Non-periodic motion : The motion which does not repeat itself after regular interval of time is called non-periodic motion.
Examples : A footballer running on a field, application of brakes in a moving vehicle, a ball rolling down the ground gradually slows down and finally stops, motion of tides in the sea, etc.

Question 13.
What is random motion. Give one example.
Answer:
Random motion— When an object in a motion has no specific path and which suddenly changes its motion is said to have a random motion.
Example : A flying kite.

Question 14.
Name the type/types of motion being performed by each of the following:
(a) Vehicle on a straight road
(b) Blades of an electric fan in motion
(c) Pendulum of a wall clock
(d) Smoke particles from chimney
(e) Hands of a clock
(f) Earth around the sun
(g) A spinning top.
Answer:
(a) Rectilinear motion
(b) Rotatory motion
(c) Oscillatory motion, periodic motion
(d) Non-periodic motion
(e) Uniform circular and periodic motion
(f) Rotatory motion, circular motion and periodic motion
(g) Rotatory motion

Question 15.
Give two examples to illustrate that a body can have two or more types of motion simultaneously.
Answer:
Sometime a body can have more than one type of motion. Such a motion is called the mixed motion.
Example :
(i) The wheels of a moving train have both the translatory as well as the rotatory motions as it moves from position A to position B while rotating.

(ii) The earth rotates about its axis (rotatory motion) and at the same time it revolves around the sun in a curved path (curvilinear or circular motion) in a fixed time interval (periodic motion).

Question 16.
State the types of motion of the following :
(a) The needle of a sewing machine
(b) The wheel of a bicycle
(c) The drill machine
(d) The carpenter’s saw
Answer:
(a) Periodic motion
(b) Rotatory motion
(c) Mixed = Translatory and Rotatory motion
(d) Mixed = Translatory and Oscillatory motion

Question 17.
Distinguish between uniform and non-uniform motions, giving an example of each.
Answer:

Question 18.
How do you determine the average speed of a body in non-uniform motion ?
Answer:
In a non-uniform motion, the average speed of a body is calculated by dividing the total distance travelled by the body, with the total time of its journey. Thus,
Average speed = Total distance travelled by the body / Total time of joumey

Question 19.
Define the term weight and state its S.I. unit.
Answer:
The weight of a body is the force with which earth attracts the body i.e. the weight of a body is the force of gravity on it. The weight of a body is not constant, but it changes from place to place. It is represented by the symbol W. The S.I. unit of weight is newton (N).

Question 20.
How are the units of weight, kgf and newton related ?
Answer:
1 kg F = 10 N

Question 21.
State three differences between mass and weight.
Answer:
Mass

It is the quantity of matter contained in a body.
Its S.J. unit is kilogram (kg)
It is constant for a body and it does not change by changing the place of the body.
It is measured by a beam balance.

Weight

It is the force with which the earth attracts the body.
Its S.I. unit is newton (N) and other unit is kilogram-force (kgf) where 1 kgf= 10N(nearly).
It is not constant for a body, but it changes from place to place.
It is measured by a spring balance.

Question 22.
Which quantity : mass or weight, does not change by change of place ?
Answer:
The mass of a body is constant and it does not change by changing the position of the body.

Question 23.
State which of the quantities, mass or weight is always directed vertically downwards.
Answer:
Mass is the quantity of matter contained in a body. Weight is the force with which the earth attracts the body. Weight is always directed vertically downwards.

 

C. Numericals

Question 1.
A car covers a distance of 160 km between two cities in 4 h. What is the average speed of the car ?
Answer:
Distance =160 km
Time taken = 4h
Speed = ?
Speed = Distance covered / Time taken
= 160km / 4h = 40 km h^-1

Question 2.
A train travels a distance of 300 km with an average speed of 60 km h_1. How much time does it take to cover the distance?
Answer:
Speed = 60 km h^-1
Distance covered = 300 km

Question 3.
A boy travels with an average speed of 10 m s^-1 for 20 min. How much distance does he travel ?
Answer:
Average speed of boy = 10 m s^-1
Time taken = 20 min
Distance travelled = Speed × Time taken
Convert minutes into seconds
1 minute = 60 sec.
20 minutes = 20 × 60 = 1200 sec.
Distance travelled = 10 m s^-1 × 1200 sec.
= 12000 m Or 12 km

Question 4.
A boy walks a distance 30 m in 1 minute and another 30 m in 1.5 minute. Describe the type of motion of the boy and find his average speed in m s-1.
Answer:
As the speed does not remain constant throughout the journey the motion is non-uniform
Total distance travelled in going and coming back
d = 30 m + 30 m = 60 m
Total time taken in going and coming back

Question 5.
A cyclist travels a distance of 1 km in the first hour, 0.5 km in the second hour and 0.3 km in the third hour. Find the average speed of the cyclist in
(i) km h^-1, (ii) m s^-1.
Answer:
(a) Distance travelled in first hour = 1 km
Distance travelled in second hour = 0.5 km
Distance travelled in third hour = 0.3 km
Total time taken = 3 hr
Total distance travelled = 1 + 0.5 + 0.3 = 1.8 km
(i) Average speed in km h^-1

Average speed in m s^-1
1 km = 1000 m
1.8 km = 1.8 × 1000 m
= 1800 m
1 hour = 3600 seconds
3 hour = 3600 × 3 = 10800 sec.

Question 6.
A car travels with speed 30 km h^-1 for 30 minute and then with speed 40 km h^-1 for one hour. Find :
(a) the total distance travelled by the car
(b) the total time of travel, and
(c) the average speed of car
Answer:
Speed of car for first 30 minutes = 30 km h^-1
Speed of car for next 1 hour = 40 km h^-1
(a) Total distance travelled by the car

Question 7.
On earth the weight of a body of mass 1.0 kg is 10 N. What will be the weight of a boy of mass 37 kg in (a) kgf (b) N ?
Answer:
Weight of a body of mass 1.0 kg body = 10 N
(a) Weight of a boy of mass = 37 kg
(b) Weight of a boy of 37 kg in newton will be 1 kgf = 10N
∴ 37 kgf = 37 × 10 N
= 370 N

Question 8.
The weight of a body of mass 6.0 kg on moon is 10 N. If a boy of mass 30 kg goes from earth to the moon surface, what will be his (a) mass, (b) weight ?
Answer:
(a) Mass remains same it does not change
So mass of boy 30 kg on earth = 30 kg on moon surface
(b) Weight of boy on moon becomes 1 / 6
∴ 30 kg boy will weight 30 x 1/6 = 5kg
1 kg = 10 N ⇒ 5 × 10 N = 50 N
∴ Weight of boy on moon surface = 50 N

 

 

 

Selina Concise Mathematics Class 7 ICSE Solutions Chapter 3 Fractions (Including Problems)

Selina Publishers Concise Mathematics Class 7 ICSE Solutions Chapter 3 Fractions (Including Problems)

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

APlusTopper.com provides step by step solutions for Selina Concise ICSE Solutions for Class 7 Mathematics. You can download the Selina Concise Mathematics ICSE Solutions for Class 7 with Free PDF download option. Selina Publishers Concise Mathematics for Class 7 ICSE Solutions all questions are solved and explained by expert mathematic teachers as per ICSE board guidelines.

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POINTS TO REMEMBER

1. Fraction. A rational number in form of — where a and b are integers is called a fraction.
   ‘a’ is called the numerator and Lb’ is called the denominator of the fraction.
2. Classification of Fractions :
   Decimal fraction : A fraction whose denominator is 10 or multiple of 10.
   Vulgur fraction : A fraction whose denominator is oilier than 10 or multiple of 10.
   Proper fraction : A fraction whose denominator is greater than its numerator.
   Improper fraction : A fraction whose denominator less than its numerator.
   Mixed fraction : A fraction which consists of an integer and a proper fraction.
   Note. If the numerator of a fraction is equal to its denominator, then the fraction is equal to unity i.e. 1.
3. Equivalent Fractions
   Fractions having the same value are called the equivalent fractions.
4. Simple and Complex Fractions
   A fraction whose numerator and denominator both are integers, is called a simple fraction.
   A fraction whose numerator or denominator or both are not integers, is called a complex fraction.
5. Like and Unlike Fractions
   Fractions having the same denominators are called like fractions.
   The fractions with different denominators are called unlike fractions.
6. Converting unlike fractions into like fractions
   Find the LCM of the denominators of all the give- fractions.
   For each given fraction, multiply its denominator by a suitable numbers so that the product obtained is equal to the LCM in (i).
   Multiply the numerator also by the same number.
7. To insert a fraction between two given fractions .
   Add the numerators as well as denominators of the given fractions. Then simplify if required.
8. Addition and Subtraction of fractions
9. For like fractions, add or subtract (as required) their numerators, keeping the denominator same.
   For unlike fractions, first change all the fractions into like fractions and then add or subtract as above given in (i).
10. Multiplication
    To multiply two or more fractions, multiply their numerators as well as their denominators.
11. Division
    To divide on fraction or integer by some other fractions or integer, multiply the first by the reciprocal of the second as given above in multiplication.
12. Using ‘BODMAS’
    The word ‘BODMAS’ is the abbreviation formed by taking the initial letters of six operations i.e. ‘Bracket’, ;OF, ‘Division’, ‘Multiplication’, ‘Addition’ and ‘Subtraction’. So, according to the rule of ‘BODMAS’, working must be done in the order corresponding to the letters in the word ‘BODMAS’.
13. Brackets and their removal
    Brackets are four kinds i.e., bar bracket , circular brackets ( ), curly brackets { } and square brackets [ ] and these can be removed in this order i.e. firstly bar, then circular, then curly and lastly square brackets keeping in considerations of the sign given before them.

Fractions Exercise 3A – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.
Classify, each fraction given below, as decimal or vulgar fraction, proper or improper fraction and mixed fraction :

Solution:
(i) Vulgar and Proper
(ii)Decimal and Improper
(iii) Decimal and Proper
(iv) Vulgar and Improper
(v) Mixed
(vi) Decimal
(vii) Mixed and Decimal
(viii) Vulgar and Proper Ans.

Question 2.
Express the following improper fractions as mixed fractions :

Solution:

Question 3.
Express the following mixed fractions as improper fractions :

Solution:

Question 4.
Reduce the given fractions to lowest terms

Solution:

Question 5.
State : true or false

Solution:

Question 6.
Distinguish each of the following fractions, given below, as a simple fraction or a complex fraction :

Solution:

Fractions Exercise 3B – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.
For each pair, given below, state whether it forms like fractions or unlike fractions :

Solution:

Question 2.
Convert given fractions into fractions with equal denominators :

Solution:

Question 3.
Convert given fractions into fractions with equal numerators :

Solution:

Question 4.
Put the given fractions in ascending order by making denominators equal :

Solution:

Question 5.
Arrange the given fractions in descending order by making numerators equal :

Solution:

Question 6.
Find the greater fraction :

Solution:

Question 7.
Insert one fraction between :

Solution:

Question 8.
Insert three fractions between

Solution:

Question 9.
Insert two fractions between

Solution:

Fractions Exercise 3C – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.
Reduce to a single fraction :

Solution:

Question 2.
Simplify :

Solution:

Question 3.
Subtract :

Solution:

Question 4.
Find the value of

Solution:

Question 5.
Simplify and reduce to a simple fraction :


Solution:

Question 6.
A bought 3 \(\frac { 3 }{ 4 }\) kg of wheat and 2 \(\frac { 1 }{ 2 }\) kg of rice. Find the total weight of wheat and rice bought.

Solution:

Question 7.
Which is greater,\(\frac { 3 }{ 5 }\) or \(\frac { 7 }{ 10 }\) and by how much?

Solution:

Question 8.
What number should be added to 8 \(\frac { 2 }{ 3 }\) to 12 \(\frac { 5 }{ 6 }\)

Solution:

Question 9.
What should be subtracted from 8\(\frac { 3 }{ 4 }\) to get 2 \(\frac { 2 }{ 3 }\)

Solution:

Question 10.
A field is 16 \(\frac { 1 }{ 2 }\) m long and 12 \(\frac { 2 }{ 5 }\) m wide. Find the perimeter of the field.
Solution:

Question 11.
Sugar costs ₹37 \(\frac { 1 }{ 2 }\)per kg. Find the cost of 8\(\frac { 3 }{ 4 }\) kg sugar.

Solution:

Question 12.
A motor cycle runs 31\(\frac { 1 }{ 4 }\) km consuming 1 litre of petrol. How much distance will it run consuming 1\(\frac { 3 }{ 5 }\) liter of petrol?

Solution:

Question 13.
A rectangular park has length = 23 \(\frac { 2 }{ 3 }\) m and breadth = 16 \(\frac { 2 }{ 3 }\) m. Find the area of the park.

Solution:

Question 14.
Each of 40 identical boxes weighs 4 \(\frac { 4 }{ 5 }\) kg Find the total weight of all the boxes.

Solution:

Question 15.
Out of 24 kg of wheat, \(\frac { 5 }{ 6 }\) th of wheat is consumed. Find, how much wheat is still left?

Solution:

Question 16.
A rod of length 2 \(\frac { 2 }{ 5 }\) metre is divided into five equal parts. Find the length of each part so obtained.

Solution:

Question 17.
IfA = 3\(\frac { 3 }{ 8 }\) and B = 6\(\frac { 5 }{ 8 }\) find :
(i) A+B
(ii) B A
Solution:

Question 18.
Cost of 3 \(\frac { 5 }{ 7 }\) litres of oil is ₹83 \(\frac { 1 }{ 2 }\). Find the
cost of one litre oil.

Solution:

Question 19.
The product of two numbers is 20 \(\frac { 5 }{ 7 }\). If one of these numbers is 6 \(\frac { 2 }{ 3 }\), find the other.
Solution:

Question 20.
By what number should 5 \(\frac { 5 }{ 6 }\) be multiplied 1 to get 3\(\frac { 1 }{ 3 }\) ?

Solution:

Fractions Exercise 3D – Selina Concise Mathematics Class 7 ICSE Solutions

Question 1.
Simplify
Solution:

Question 2.

Solution:

Question 3.

Solution:

Question 4.

Solution:

Question 5.

Solution:

Question 6.

Solution:

Question 7.

Solution:

Question 8.

Solution:

Question 9.

Solution:

Question 10.

Solution:

Question 11.

Solution:

EXERCISE 3 (E)

Question 1.
A line AB is of length 6 cm. Another line CD is of length 15 cm. What fraction is :
(i) The length of AB to that of CD ?
(ii) \(\frac { 1 }{ 2 }\) the length of AB to that of \(\frac { 1 }{ 3 }\) of CD ?
(iii) \(\frac { 1 }{ 5 }\) of CD to that of AB ?

Solution:

Question 2.
Subtract \(\frac { 2 }{ 7 }\) – \(\frac { 5 }{ 21 }\) from the sum of \(\frac { 3 }{ 4 }\) , \(\frac { 5 }{ 7 }\) and \(\frac { 7 }{ 12 }\)

Solution:

Question 3.
From a sack of potatoes weighing 120 kg, a merchant sells portions weighing 6 kg, 5\(\frac { 1 }{ 4 }\) kg, 9\(\frac { 1 }{ 2 }\) kg and 9\(\frac { 3 }{ 4 }\) kg respectively.
(i) How many kg did he sell ?
(ii) How many kg are still left in the sack ?

Solution:

Question 4.
If a boy works for six consecutive days for 8 hours, 7\(\frac { 1 }{ 2 }\) hours, 8\(\frac { 1 }{ 4 }\) hours, 6 \(\frac { 1 }{ 4 }\)4 3hours, 6\(\frac { 3 }{ 4 }\) hours and 7 hours respectively. How much money will he earn at the rate of Rs. 36 per hour ?

Solution:

Question 5.
A student bought 4 \(\frac { 1 }{ 3 }\) m of yellow ribbon, 6 \(\frac { 1 }{ 6 }\) m of red ribbon and 3\(\frac { 2 }{ 9 }\) m of blue ribbon for decorating a room. How many metres of ribbon did he buy ?

Solution:

Question 6.
In a business, Ram and Deepak invest \(\frac { 3 }{ 5 }\) and \(\frac { 2 }{ 5 }\) of the total investment. IfRs. 40,000 is the total investment, calculate the amount invested by each ?

Solution:

Question 7.
Geeta had 30 problems for home work. She worked out \(\frac { 2 }{ 5 }\) of them. How many problems were still left to be worked out by her ?

Solution:

Question 8.
A picture was marked at Rs. 90. It was sold at \(\frac { 3 }{ 4 }\) of its marked price. What was the sale price ?

Solution:

Question 9.
Mani had sent fifteen parcels of oranges. What was the total weight of the parcels, if each weighed 10\(\frac { 1 }{ 2 }\) kg ?

Solution:

Question 10.
A rope is 25\(\frac { 1 }{ 2 }\) m long. How many pieces , 1 \(\frac { 1 }{ 2 }\) each of length can be cut out from it?

Solution:

Question 11.
The heights of two vertical poles, above the earth’s surface, are 14 \(\frac { 1 }{ 4 }\) m and 22 \(\frac { 1 }{ 3 }\) respectively. How much higher is the second pole as compared with the height of the first pole ?

Solution:

Question 12.
Vijay weighed 65\(\frac { 1 }{ 2 }\) kg. He gained 1\(\frac { 2 }{ 5 }\) kg during the first week, 1 \(\frac { 1 }{ 4 }\) kg during the second week, but lost \(\frac { 5 }{ 16 }\) kg during the 16 third week. What was his weight after the third week ?

Solution:

Question 13.
A man spends \(\frac { 2 }{ 5 }\) of his salary on food and \(\frac { 3 }{ 10 }\) on house rent, electricity, etc. What fraction of his salary is still left with him ?
Solution:

Question 14.
A man spends \(\frac { 2 }{ 5 }\) of his salary on food and \(\frac { 3 }{ 10 }\) of the remaining on house rent, electricity, etc. What fraction of his salary is still left with him ?

Solution:

Question 15.
Shyam bought a refrigerator for Rs. 5000. He paid \(\frac { 1 }{ 10 }\) of the price in cash and the rest in 12 equal monthly instalments. How much had he to pay each month ?

Solution:

Question 16.
A lamp post has half of its length in mud, and \(\frac { 1 }{ 3 }\) of its length in water.
(i) What fraction of its length is above the water ?
(ii) If 3\(\frac { 1 }{ 3 }\) m of the lamp post is above the water, find the whole length of the lamp post.
Solution:

Question 17.
I spent \(\frac { 3 }{ 5 }\) of my savings and still have Rs. 2,000 left. What were my savings ?

Solution:

Question 18.
In a school, \(\frac { 4 }{ 5 }\) of the children are boys. If the number of girls is 200, find the number of boys.

Solution:

Question 19.
If \(\frac { 4 }{ 5 }\) of an estate is worth Rs. 42,000, find the worth of whole estate. Also, find the value of \(\frac { 3 }{ 7 }\) of it.
Solution:

Question 20.
After going \(\frac { 3 }{ 4 }\) of my journey, I find that I have covered 16 km. How much Journey is still left ?

Solution:

Question 21.
When Krishna travelled 25 km, he found that \(\frac { 3 }{ 5 }\) of his journey was still left. What was the length of the whole journey.

Solution:

Question 22.
From a piece of land, one-third is bought by Rajesh and one-third of remaining is bought by Manoj. If 600 m² land is still left unsold, find the total area of the piece of land.
Solution:

Question 23.
A boy spent \(\frac { 3 }{ 5 }\) of his money on buying 1 cloth and \(\frac { 1 }{ 4 }\) of the remaining on buying shoes. If initially he has ?2,400; how much did he spend on shoes?

Solution:

Question 24.
A boy spent \(\frac { 3 }{ 5 }\) of his money on buying cloth and \(\frac { 1 }{ 4 }\) of his money on buying shoes. If initially he has ?2,400; how much did he spend on shoes?

Solution: