Kashish was doing some activity in laboratory. Her teacher asked her to dissolved a chemical in water and touch the outer surface of the beaker. She felt the surface hot. What does it depict?

Give reasons for the following:

Expansion and contraction are maximum in gases.

Give reasons for the following:

Silver pieces of jewellery tarnish when exposed to air.

Give reasons for the following:

Apples and some other fruits turn brown when cut surface is exposed to air.

Name the type of changes that occur in the burning of a candle. Explain with reason.