States of Matter: Gas Pressure

Understanding gas pressure starts from understanding the behaviour of gas particles. Gas particles move quickly in all directions, have fast, random motion and collide with each other and their container’s walls.
The pressure exerted by a gas is a result of the force it applies on a unit area due to these collisions. The harder and more frequently the particles hit the walls of their container, the greater the gas pressure.
When a gas is heated, the particles gain more kinetic energy and therefore move faster, causing more collisions with the container’s walls and increasing the pressure.
If the volume of the container is increased at constant temperature (like inflating a balloon), the particles have a larger space to move in. This results in fewer collisions with the container’s walls, and hence, the pressure decreases. This is explained by Boyle’s Law, which states that the pressure and volume of a gas have an inverse relationship when the temperature is kept constant.
Similarly, by decreasing the volume in which gas particles move (like deflating a balloon), the frequency of their collisions with container walls increases and so does the pressure.
When additional gas is added to a container with a fixed volume, this increases the number of particles inside and thus boosts the frequency of collisions with the container walls, increasing the overall pressure.
Conversely, if gas escapes from a container, the number of particles and their collisions with container wall decrease, resulting in a drop in pressure.
It’s also important to note that atmospheric pressure is caused by the weight of air molecules in the atmosphere above us. Hence, the higher the altitude, the fewer air molecules above, resulting in lower atmospheric pressure.
Finally, remember that all gases exert pressure, regardless of their weight or size. This is because gas pressure is not dependent on the type of gas but rather on its temperature, volume, and the number of particles.

Remember to think through these principles and visualise the behaviour of gas particles to understand how changes in their environment affect gas pressure.