Question

Answer in Brief. (5-7 lines).

Q1) No new substance are formed at the end of a physical change. Give Reason.

Q2) How can we show that the vapours form boiling water contain water?

Answer 1

Ans..1...

A physical change is change in the physical properties of a "substance" but it doesn't change the substance.

The substance can be changed into another only by change in its chemical composition.
Because two substance are different because of their different chemical composition.

Chemical composition is the parameter which separates one substance from other.

physical changes doesn't affect chemical composition.
substance changes when two or more substance combined or break up.

ans 2....

vapours are created by raising the temperature of water.
If we collect some water vapour and cool it , we will get dense water vapour as form of drops.