Here's why:

* Heat is a form of energy: It's the energy that comes from the movement of atoms and molecules within a substance.

* Higher temperature means faster movement: The higher the temperature of a substance, the faster its particles move.

* Heat transfer: Heat can be transferred from one object to another, causing the particles in the receiving object to move faster and its temperature to increase.

Let me know if you'd like to learn more about heat transfer or the different ways heat affects matter!