What happens when water inside gets hot?

When water gets hot, it moves faster and wants to escape more than when it’s cool.

Imagine you're playing with your favorite toy car on a smooth floor, that's like water at room temperature, moving along nicely. Now picture the floor getting really bumpy and warm, almost like it's dancing. That's what happens to water inside something when it gets hot: the water molecules start to move around more quickly, just like you would if you were running on a bouncy castle.

When you heat up water, maybe by putting it near a stove or in the sun, it starts to behave like a group of kids who are all excited and can't sit still. Hot water molecules are more energetic, so they push against each other harder and try to move upward, just like how hot air rises.

If you put a lid on a pot while heating it up, you might notice the steam pushing against the lid, that's the water trying to escape because it's too hot and too active to stay still inside.