Temperature is a measure of the average kinetic energy of the tiny particles that make up a substance. Think of the particles as dancers at a party: the hotter the party, the faster they move around. The cooler the party, the slower they shuffle. The speed of the dancers (particles) tells us how hot or cold the party (material) is.
The kinetic energy of a single particle is given by
\$E_k = \frac{1}{2}mv^2\$.
When many particles are moving, the average of all their kinetic energies is what we call temperature. A higher average speed (more kinetic energy) → higher temperature. A lower average speed → lower temperature.
If you imagine a crowd of people at a concert, the louder the crowd (more energy), the warmer the room feels. Similarly, in a gas, the faster the molecules move, the hotter the gas feels.
Absolute zero is the theoretical temperature at which particles would have *no* kinetic energy left. It is defined as
\$0\,\text{K} = -273.15\,^\circ\text{C}\$.
At this point, the particles would be completely still, like a frozen dance floor where no one moves. In reality, quantum mechanics tells us that particles still have a tiny amount of motion called zero‑point energy, but for everyday physics we treat absolute zero as the lowest possible temperature.
| Temperature (°C) | Average Kinetic Energy per Particle (J) |
|---|---|
| 0 | ≈ 0.025 |
| 100 | ≈ 0.026 |
| -273.15 (Absolute Zero) | ≈ 0 |