Name one common substance which can be easily changed from one state to another by heating or cooling.

What is meant by saying that the latent heat of vaporization of water is 22.5 × 10⁵J/kg?

Name the temperature at which:

(a) A liquid changes into a gas

(b) A solid changes into a liquid.

What is the mane of the process in which:

(a) A solid turns directly into a gas?

(b) A gas turns directly into a solid?

Name one property which is shown by ammonium chloride but not by sodium chloride.