Here's why:

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

* Increased Vibrations and Movement: As temperature rises, particles absorb more energy. This energy causes them to vibrate faster and move around more rapidly.

* Gas vs. Liquid vs. Solid: The effect of temperature on particle speed is most pronounced in gases, where particles are relatively far apart and can move freely. In liquids, particles are closer together, so their movement is more restricted. In solids, particles are tightly packed and their movement is primarily vibrational.

Think of it this way: Imagine a group of people standing still (low temperature). Now, imagine them getting excited and moving around more (higher temperature). The overall speed of the people in the group has increased.

Important Note: While increased temperature generally means increased particle speed, it's not a simple one-to-one relationship. Factors like the type of substance and its phase (solid, liquid, gas) influence how particle speed changes with temperature.