An empty glass bottle is fitted with a narrow tube at its mouth. The open end of the tube is kept in a beaker containing water. When the bottle is heated, bubbles of air are seen escaping into water. Explain the reason.

State which expands more, when heated to the same temperature: solid, liquid or gas?

Name the mode of transfer of heat in the following:

(a) solid

(b) liquid

(c) gas

(d) vacuum.

What are good and bad conductors of heat? Give two examples of each.