What is the relationship between energy and temperature?
Temperature is the average kinetic energy of a substance, and a measure of how hot or cold something is.
As a substance gains kinetic energy, its particles begin to move faster. While solids vibrate in place, the particles in a liquid slip and slide past each other, and in gasses the particles move even faster and further apart.
As the kinetic energy of a substance increases, the particles collide with one another with greater force and frequency. Every time particles collide, there is friction between them. Just as your hands get warm when you rub them together, the particles begin to warm as they collide. This is why there is a direct relationship between the temperature and the kinetic energy of a substance.