Expansion and contraction of gases


•    Gases that are heated expand in their containers.

•    The energy of the gas particles increase by heating.

•    The particles of warm gases hit the walls of the container and they hit it harder.

•    If the walls of the container are flexible, the walls expand.

•    If the walls are not flexible and cannot expand, then the pressure inside the container increases.

•    A few examples of gases that expand and contract are:

     (i)    Air in balloons

     (ii)   Air in tyres

     (iii)  Air in an air mattress

     (iv)  Air in a football, volleyball, etc

•    The helium gas in a balloon expands when we move a balloon from the cold outdoors to a warm room.

•    At a low temperature, the average kinetic energy of the particles in the balloon is low.

•    The particles do not collide as often with the walls of the balloon, and hit the walls with less force. So, the balloon contracts.

•    As the temperature of the gas inside the balloon rises, the particles move faster and hit the wall of the balloon more often. So, the balloon expands.


Cars and bicycles:


•    When cars and bicycles travel, their tyres rub on the road.

•    This makes the tyres get hot. The air inside the tyres will expand.

•    If the tyres are too full, they could burst.


Sports balls:

•    Sports balls such as footballs are also filled with air.

•    If we leave a football out in the cold, the air inside the ball will contract. The ball will get soft and it will become unusable.