Temperature increases when particles are moving faster on average.

Here's why:

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

* Faster-moving particles have more kinetic energy. The more they move, the more energy they possess.

* Therefore, if particles are moving faster on average, the average kinetic energy increases, and so does the temperature.

Think of it like this: imagine a pot of water on a stove. As the water heats up, the water molecules move faster and faster. This increased movement translates to a higher temperature.