According to the kinetic theory of matter, the particles in a substance are in constant motion. The temperature of a substance is a measure of the average kinetic energy of the particles. As the temperature increases, the average kinetic energy of the particles increases, and therefore the particles move faster.
Here's a simple analogy to help you understand the relationship between temperature and particle speed:
Imagine a pot of water boiling on a stove. When the water is cold, the water molecules are moving slowly and there is not a lot of activity in the pot. As the water starts to heat up, the water molecules begin to move faster and the water starts to bubble. When the water is boiling, the water molecules are moving very quickly and the water is vigorously bubbling. The faster movement of the water molecules in the boiling water is analogous to the increased speed of particles in a substance as temperature increases.
