Question

why does the volume of a substance contract when it loses heat/energy? because its molecules move further apart because its molecules move closer together

Explanation:

When a substance loses heat/energy, its temperature decreases. According to the kinetic - molecular theory of matter, the kinetic energy of molecules is related to temperature. As temperature drops, the kinetic energy of molecules decreases. Molecules have less energy to move around vigorously. So, they move closer together. This reduction in the average distance between molecules leads to a contraction in the volume of the substance.

Answer:

because its molecules move closer together