Living Science Chemistry Class 6 ICSE Solutions Chapter 3 Element and Compounds

ICSE Living Science Chemistry for Class 6 Solutions Chapter 3 Element and Compounds

Check Your Progress Fill In The Blanks

Question 1.
…………….. are good conductors of heat and electricity. (Metals/Non-metals)
Answer:
Metals are good conductors of heat and electricity.

Question 2.
The elements that do not react chemically are called …………….
Answer:
The elements that do not react chemically are called noble or inert gases.

Question 3.
Element are represented by …………..
Answer:
Element are represented by symbols.

Question 4.
The symbol of sodium is …………
Answer:
The symbol of sodium is Na.

Question 5.
The elements present in common salt are …………. and
Answer:
The elements present in common salt are sodium and chlorine.

A. Tick the most appropriate answer

Question 1.
Which of the following is a metal ?
a. Sulphur
b. Chlorine
c. Gold
d. Bromine
Answer:
c. Gold

Question 2.
Which of the following is a non-metal ?
a. Silver
b. Iodine
c. Copper
d. Iron
Answer:
b. Iodine

Question 3.
Which of the following is a metalloid ?
a. Copper
b. Silver
c. Oxygen
d. Silicon
Answer:
d. Silicon

Question 4.
The symbol of iron is –
a. I
b. Fe
c. In
d. Na
Answer:
b. Fe

Question 5.
Atoms of different elements combine to form a molecule of –
a. an element
b. a compound
c. either an element or a compound
d. cannot say
Answer:
b. a compound

B. Fill in the blanks.

Question 1.
Pure substances are classified into ……………… and ………………
Answer:
Pure substances are classified into elements and compounds.

Question 2.
The ………………… of an element is the abbreviation of its full name.
Answer:
The symbol of an element is the abbreviation of its full name.

Question 3.
Natrium is the Latin name of ………………..
Answer:
Natrium is the Latin name of sodium.

Question 4.
The symbol of cobalt is ………………
Answer:
The symbol of cobalt is Co.

Question 5.
The molecular formula of water is ………………
Answer:
The molecular formula of water is HzO.

C. State if the following statements are true or false. Correct the statement if it is false

Question 1.
A pure substance consists of a single type of particle.
Answer:
True

Question 2.
Some metals exist as gases.
Answer:
False. No metals exist as gases.

Question 3.
Sulphur is a metalloid
Answer:
False. Sulphur is a non-metal.

Question 4.
Compounds are substances made up of two or more elements.
Answer:
True

Question 5.
A molecule of hydrogen is made up of three atoms of hydrogen.
Answer:
False. A molecule of hydrogen is made up of two atoms of hydrogen.

D. Match the following

1. Smallest unit of a compound	a. molecule
2. Sulphur	b. noble gas
3. Helium	c. non-metal
4. A diatomic molecule	d. sodium
5. An element having valency one	e. hydrogen
	f. metalloid

Answer:

1. Smallest unit of a compound	a. molecule
2. Sulphur	c. non-metal
3. Helium	b. noble gas
4. A diatomic molecule	e. hydrogen
5. An element having valency one	d. sodium

E. Name the following

Question 1.
Elements that do not react chemically
Answer:
Inert or noble gases

Question 2.
Elements showing properties of both metals and non-metals
Answer:
Metalloids

Question 3.
The smallest particle of an element or a compound which has independent existence
Answer:
Molecule

Question 4.
The number of atoms present in one molecule of an element.
Answer:
Atomicity

F. Write the chemical formulae of the following compounds.
1. Water
2. Carbon dioxide
3. Zinc sulphide
4. Calcium oxide
Answer:
1. Chemical formula of water

Formula H₂O₁ = H₂O

2. Chemical formula of carbon dioxide Carbon Oxygen

Formula C₂O₄ = CO₂

3. Chemical formula of zinc sulphide

Formula Zn₂S₂ = ZnS

4. Chemical formula of calcium oxide

Formula Ca₂O₂ = CaO

G. Answer the following in short.

Question 1.
What are the two types of pure substances ?
Answer:
Two types of pure substances are elements and compounds.

Question 2.
What is a compound ?
Answer:
A compound is a substance made up of two or more elements chemically combined together in a fixed ratio.

Question 3.
What is a molecule ?
Answer:
A molecule is the smallest particle of an element or a compound that has independent existence and shows all the properties of that substance.

Question 4.
Which can exist independently-atoms or molecules ?
Answer:
Atoms of very’ elements like noble gases can exist indepedently.
Molecules can exist independently.

Question 5.
What is a molecular formula ?
Answer:
The molecular formula represents the composition of a molecule of an element or compound. The molecular formula of a substance is also known as its chemical formula.

H. Answer the following in detail.

Question 1.
What are the four groups into which all the elements are classified ? Name two of each group.
Answer:
The four groups into which all the elements are classified are :

1. Metals – Examples : Iron, gold, copper, silver, sodium, etc.
2. Non-metals – Examples : Carbon, hydrogen, oxygen, sulphur, iodine, etc.
3. Metalloids – Examples : Silicon, germanium, arsenic and antimony.
4. Noble or inert gases – Examples : Helium, neon, argon, krypton, xenon and radon.

Question 2.
What is meant by the symbol of an element ? State the symbols for sodium, iron, copper and silver.
Answer:
The symbol of an element is a single-letter or two-letter abbreviation (short name) of its full name.
Sodium – Na
Iron – Fe
Copper – Cu
Silver – Ag

Question 3.
State three characteristics of a compound.
Answer:
Characteristics of a compound :
1. Compounds are made up of two or more elements. For example, the compound water is made up of the elements hydrogen and oxygen.
2. A compound is always made up of the same elements combined together in a fixed ratio. For example, in water, two elements hydrogen and oxygen are chemically combined together in a fixed ratio of two atoms of hydrogen to one atom of oxygen.
3. The properties of a compound are different from those of its constituent elements. For example, the element hydrogen can bum and the element oxygen helps in burning. However, the compound water, formed from hydrogen and oxygen, neither bums nor helps in burning. Hydrogen and oxygen are gases but their compound water is a liquid.
4. A compound is always homogenous, that is, all samples of a compound are identical in composition and have the same properties throughout.
5. It is not possible to separate the constituents of a compound by physical means.
6. Energy is usually given off or absorbed when a compound is formed.

Question 4.
State two differences between an element and a compound.
Answer:

I. Give reasons for the following

Question 1.
The atoms of gold are different from the atoms of silver.
Answer:
The atoms of gold are different from the atoms of silver as gold and silver are different elements. The atoms of one element are different from those of other elements and they have different properties.

Question 2.
Noble gases are monoatomic.
Answer:
Noble or inert gases are stable and do not react chemically. Noble gases exist as single atoms and these single atoms are also the molecules of the respective elements and hence, are called monoatomic molecules.

Living Science Chemistry Class 6 ICSE Solutions