Question

Why are liquids and gases normally insulators of heat?

Answer 1

Solids have high intermolecular attractive forces. So, the atoms and molecules of solids are close to each other. When heat is supplied, the atoms or molecules vibrate, and as atoms are close, the vibrations are easily passed from one atom to another, thus conducting heat easily.

Liquids and gases have lower intermolecular attractive forces. So, the molecules are far apart. When heat is supplied, the vibrations cannot be transferred(supplied) easily to other molecules, as they are far apart. So, they are bad conductors of heat or, insulators of heat.