Here's why:
* Temperature is a measure of the average kinetic energy of the particles in a substance. Kinetic energy is the energy of motion. The faster the atoms are moving, the higher their kinetic energy, and the higher the temperature.
* Atoms are constantly in motion. Even in solids, where atoms are tightly bound, they vibrate. In liquids, they move more freely, and in gases, they move very rapidly.
* Temperature scales (Celsius, Fahrenheit, Kelvin) are designed to quantify this atomic motion.
Important Note: While temperature is a measure of the average kinetic energy, individual atoms can move at different speeds. The average speed is what determines the overall temperature.
