Pressure Exerted by Gases

It is easier to crush an open bottle.

But crushing the same bottle which is closed and filled with air becomes a bit difficult.

If a balloon is filled with air, it acquires some shape.

The reason behind the difficulty in crushing the closed bottle. And also the balloon getting the shape is that the air molecules exert force.

Also, there is pressure generated from inside the bottle or the balloon.

Let's study the pressure exerted by gases.

Pressure is defined as the force acting on a body per unit area.

The SI unit of pressure is Pascal or .

The direction of pressure is perpendicular to the surface.

Consider when the water bottle is open. It can be easily compressed by our hand.

But when the air is filled inside the bottle and the cap is closed then it is very hard to press it.

Because in the open bottle, all the air molecules move outside on applying the force.

And in a closed bottle, air molecules are unable to escape and on applying force from outside, it also opposes the compression of the bottle.

Now, consider another example. We have seen that when there is no air inside the ballon, its shape is small and elastic.

And when there is air filled inside the ballon, it expands and acquires a particular shape.

The reason is that when we fill the air inside the balloon, the air molecules apply forces on the wall of balloon.

When we fill the air inside the balloon, the air molecules come closer.

And when they come closer, they apply pressure on wall of the balloon.

So, we have understood that the gas also exerts pressure.

Revision

Gases exert pressure on the body.

Pressure is defined as the force acting on the body per unit area.

The SI unit of pressure is Pascal or .

The End