A substance has a melting point of -7 degrees Celsius and a boiling point of 63 degrees Celsius. At which temperature is the substance a liquid.

Explanation:

Basically, Kinetic Molecular Theory says that gas particles are in constant motion and that they show perfectly elastic collisions.

An elastic collision is a collision in which there is no net loss in kinetic energy in the system as a result of the collision.

So the kinetic molecular theory says that gas particles stay moving constantly and don't lose energy when they run into each other.

Hope this helps!