Physical and chemical change

Question 1  What is a physical change.Give example?

Question 2 What is a chemical change.Give example ?

Question 3 Give the main differences between physical and chemical change?

Physical and Chemical changes

Physical changes
The changes in which no new substance are formed,are called physical changes.

In a physical change,the substances involved do not change their identity.They can be easily returned to their original form by some physical changes.

For Ex:Freezing of water,Boiling of water,Condensation of steam,Making a solution,Glowing of electric bulb,stretching of rubber band,cutting or tearing a piece of paper etc.

Chemical Changes
The changes in which new substance are formed,are called chemical changes.

In a chemical change,the substances involved change their identity ie they get converted into entirely new substance.

For Ex:Burning of magnesium ribbon,Rusting of iron,Formation of curd from milk,Cooking of food etc.

   Physical change  Chemical Change
1)No new substance is formed in the physical change. A new substance is formed in a chemical change.
2)Physical change is temporary change. A chemical change is a permanent change.
3)Physical change is reversible. Chemical change is irreversible.
4)Very little heat or light energy is usually absorbed or given out in a physical change A lot of heat or light energy is absorbed or given out in a chemical change.
5)The mass of a substance does not alter in a physical change The mass of a substance does alter in a chemical change.
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