If a substance is not at its melting or boiling point, as the heat content of a sample of matter increases,

Explanation:

If a substance is not at its melting or boiling point, as the heat content of a sample of matter increases, then there will be increase in temperature of substance. This leads to breakage of bonds between the particles.

As a result, particles will start to move which leads to increase in their kinetic energy. Hence, there will be increase in space between the particles.

Number of collisions will also increase between the particles. Therefore, they will move rapidly here and there.