Scientists use temperature to measure when a liquid turns into a solid. This process is called freezing, and the temperature at which it occurs is known as the freezing point.

Here's why:

* Temperature is a measure of the average kinetic energy of molecules. When a liquid cools, its molecules slow down, and their kinetic energy decreases.

* At the freezing point, the molecules have just enough energy to overcome their intermolecular forces and transition from a liquid to a solid state. The specific freezing point depends on the substance in question.

Of course, pressure also plays a role in the freezing process, but for most everyday situations, the change in pressure is negligible.