What happens to the energy of molecules when temperature increases?

When the temperature of a substance increases, the energy of the molecules generally increases. This is primarily due to an increase in their kinetic energy. Kinetic energy is the energy possessed by an object due to its motion, and in the context of molecules, it refers to how quickly they are moving.

As the temperature rises, the average speed of the molecules increases, leading to a greater kinetic energy. This relationship is described by the kinetic molecular theory, which states that temperature is a measure of the average kinetic energy of the particles in a substance. When molecules move faster, they collide more often and with greater force, which can result in changes to the state of matter, such as from solid to liquid or liquid to gas, but fundamentally, their kinetic energy is what increases with temperature.

The other options do not align with this scientific principle. For example, a decrease in kinetic energy or remaining constant would contradict the established understanding of how temperature relates to molecular motion. The statement about freezing also does not apply as freezing generally occurs at lower temperatures, not as temperature increases.