ICSE Class 7 Chemistry Important Questions Chapter 2 Physical and Chemical Changes 

Chemistry ICSE Class 7 Important Questions Chapter 2 Physical and Chemical Changes

Question 1.
Why is dissolution of common salt in water a physical change ?
Answer:
When we heat the salt solution until all the water evoporates, a white residue is left behind. It is salt. It proves that no new substance is formed by dissolving salt in water and the process can be reversed. Thus, dissolving common salt in water is a physical change!

Question 2.
List few conditions necessary for chemical reactions.
Answer:
A chemical reaction takes place when one or more of the following conditions are fulfilled or satisfied :

1. Close contact
2. Solution form
3. Heat
4. Light
5. Electricity
6. Pressure
7. Catalyst

Question 3.
What is the need to balance a chemical equation ?
Answer:
Balancing a chemical equation is done to show that matter is conserved and the mass of reactants is equal to mass of the products (law of conservation of mass).

Question 4.
Name four types of chemical reactions.
Answer:

1. Combination reaction
2. Decomposition reaction
3. Simple displacement reaction
4. Double displacement reaction.

Question 5.
Fill in the blanks.
1. Magnetization of iron is a ………….. change while burning of a candle is a……….. change.
Answer:
Magnetization of iron is a physical change while burning of a candle is a chemical change.

2. During a chemical reaction, the atoms just get …………….
Answer:
During a chemical reaction, the atoms just get rearranged.

3. Equations are balanced by …………… method.
Answer:
Equations are balanced by trial and error method.

4. A type of chemical reaction in which one element displaces another element from its compound is called ……………. reaction.
Answer:
A type of chemical reaction in which one element displaces another element from its compound is called single displacement reaction.

5. A type of chemical reaction in which two compounds in solution react by an exchange of ions to form two new compounds is called …………………. reaction.
Answer:
A type of chemical reaction in which two compounds in solution react by an exchange of ions to form two new compounds is called double displacement  reaction.

ICSE Class 7 Chemistry Important Questions