What is Charles' Law?

Charles' Law is about how gases behave when they get warmer or cooler.

Imagine you have a balloon full of air, and it's on a sunny day, the air inside gets warm, and poof, the balloon grows bigger! Now, if that same balloon goes into the freezer, the air cools down, and squeak, the balloon shrinks. That’s Charles' Law in action: when a gas is heated, it expands; when it's cooled, it contracts, as long as the pressure stays the same.

Think of popcorn kernels in a microwave. When you heat them up, they pop and expand, just like the air in your balloon! The more heat you add to a gas, the more it wants to take up space. If you have a container that can stretch or shrink (like a balloon), the gas will make it bigger when warm and smaller when cool.

You’ve probably seen this with a bicycle pump. When you push down on the pump, you're making the air inside hotter, that’s why sometimes your tire feels warmer after you inflate it! If you let the air cool down again, it will take up less space. That’s Charles’ Law working in real life, no magic needed, just warm, expanding air.