Q1.  Name the following:

1)  The brownish film on the iron gate.
Ans: 
Rust

2)  The process of depositing a layer of zinc on iron
Ans: 
Galvanisation

3)  The layer in our atmosphere that protects us from ultraviolet rays of the sun.
Ans:
  Ozone

4)  A change in which one or more new substances are formed.
Ans:  Chemical change.

Q2.  Answer the following questions :

1.  What is crystallisation?
Ans:
  The process by which large crystals of pure substances are formed from their solutions is called crystallization.

2.  Which are the two types of changes?
Ans: 
The two types of changes are physical and chemical change.

3.  Distinguish between Physical change and Chemical Change.
Ans: 
    Physical change                                Chemical change

a) No new substances are formed            a) New substances are formed.

b) Changes are reversible.                         b) Changes are irreversible.

c) E.g : melting of wax                                c) E.g : Digestion of food .


4.  What is the requirement for rusting?
Ans:  For rusting presence of oxygen, water and iron is essential.

5.  How does ozone protect us from the ultraviolet rays of the sun?
Ans: 
Ozone absorbs the ultraviolet radiation and breaks it down to oxygen which is used by all living beings. Hence ozone protects us from the radiation.

6.  List some characteristics of chemical change .
Ans:

a) A new substance is formed.
b) Heat, light or any other radiation may be given off or absorbed.
c) Sound may be produced.
d) A colour change may take place.