Gas in a box

Imagine you have a box, and inside that box there are little tiny things zooming around. Those little tiny things are called molecules. These molecules can be different kinds of gas, like oxygen or helium.

When you heat up the box, the molecules start moving faster and faster. This makes them bump into each other and into the sides of the box more often, which creates pressure.

If you add more gas molecules to the box, the pressure will increase because there are more little things crashing into each other and into the sides of the box at the same time.

When you open the box, the gas molecules will spread out and go everywhere. They do this because they want to be evenly spaced out, and when they're all bunched up in a small space, they don't have as much room to move around.

So, that's gas in a box! Lots of little molecules bouncing around and creating pressure when heated up, and spreading out when given more space.