Behaviour of matter - Pressure in gases
If you ride your bike over a bump in the road, you will be pleased that gases exert pressure on the walls of their container. A pumped-up tyre cushions the rider against bumps, but a flat tyre does not. The pressure of the air inside a flat tyre is just too low to do this.
Bumping particles
The particles in a gas move quickly in all directions, but they don't get far before they bump into each other or the walls of their container. When gas particles hit the walls of their container they cause pressure. The more particles that hit the walls, the higher the pressure.
This is why the pressure in a tyre or balloon goes up when more air is pumped in.
Heating increases pressure
If a gas is heated up, its particles move around more quickly. They hit the walls of their container harder and more often. This increases the pressure. Sometimes the pressure gets so great that the container bursts.
This is why balloons and tyyres burst if you blow them up too much. It's also why deodorant spray cans carry warning signs to tell you not to leave them in the sunshine. If they get too hot they explode.
© MMIX