Here's why:

* Temperature is a measure of the average kinetic energy of particles. Kinetic energy is the energy of motion.

* As temperature increases, the average kinetic energy of the particles increases. This means they are moving faster on average.

* At lower temperatures, particles have less kinetic energy and move slower.

Think of it like this: Imagine a group of people huddled together in a cold room. They're not moving much. Now imagine that same group of people in a hot room. They're more likely to be moving around, talking, and maybe even dancing! The same principle applies to the particles within matter.