Freezing

When a liquid is exposed to cold air, the particles of that liquid again start to slow down, come closer together, and form a solid.

We use water as an example to explain freezing. The particles that make up water start to slow down, giving them time to come together and form a solid.
The solid in this case is once again, an ice cube. So, to turn a liquid back into a solid, you use the freezing method.

Water freezing onto a tree, forming icicles