Here's why:

* Temperature and Kinetic Energy: Temperature is a measure of the average kinetic energy of the molecules in a substance. Kinetic energy is the energy of motion.

* Heat and Molecular Motion: When you add heat to a gas, you are increasing the energy of the molecules. This extra energy is primarily converted into faster motion, causing the molecules to move around more quickly.

* Increased Collisions: As the molecules move faster, they collide with each other and the walls of their container more frequently and with greater force.

Think of it like this: Imagine a bunch of bouncy balls in a box. The warmer the box, the faster the balls will bounce around.