Everything around you is made of tiny pieces too small to see. When something is a solid, like an ice cube or a crayon, those tiny pieces are packed close together and hold their shape. That is why a solid stays the same shape until something changes it.

When you add heat to a solid, the tiny pieces start to move faster and slide apart. This is called melting. Melting turns a solid into a liquid, like when an ice cube warms up and becomes a puddle of water.

Freezing is the opposite of melting. When you take heat away from a liquid and let it get cold, the tiny pieces slow down and lock together again. Freezing turns a liquid back into a solid, like water becoming ice in the freezer.

Here is the coolest part: it is the same material the whole time. Water and ice are both made of the same stuff, just warmer or colder. Melting and freezing only change how the material looks and feels, not what it is made of.

Every material has its own temperature where it melts. Ice melts when it gets warmer than 32 degrees Fahrenheit, but a metal spoon needs to get very, very hot before it will melt. Butter and chocolate melt easily in your warm hand.

You see melting and freezing all around you. Popsicles melt on a hot day, cheese melts on a pizza, and water freezes into ice cubes for your drink. Cooks and factory workers use melting and freezing to make food and shape many things we use.