Here's why:

* States of Matter: Matter exists in three primary states: solid, liquid, and gas. These states are determined by the arrangement and movement of the molecules within the substance.

* Freezing Point: Every liquid has a specific temperature at which it transitions from a liquid to a solid. This is called the freezing point.

* Molecular Arrangement: As a liquid cools, the molecules slow down and lose energy. When the temperature reaches the freezing point, the molecules lose enough energy to become tightly packed in a fixed, ordered arrangement, forming a solid.

Example: When water cools below 0°C (32°F), it freezes and becomes ice.