Gas Pressure:

Unlike most of the liquids, gases can be compressed. This is why it is probable to fill up hundreds of balloons with a single, small tank of helium gas and why it is probable for a scuba diver to breathe for a long time from a single small tank of air.

Visualize a container whose volume (in meters cubed) is equivalent to V. Assume that there are N moles of atoms of a specific gas inside this container that is surrounded by a perfect vacuum. We can say assured things about the pressure P, in newtons per meter squared, which the gas applies outward on the walls of the container. At first, P is proportional to N, given that V is held constant. Secondly, if V increases whereas N stays constant, P will decrease. These things are obvious intuitively.

There is another significant factor-temperature-included when it comes to gases under pressure whenever they expand and contract. The involvement of temperature T, usually measured in degrees over absolute zero, is significant and expected in gases. Whenever a parcel of gas is compressed, it heats up; whenever it is decompressed, it cool off. Heating up a parcel of gas will raise the pressure, when all other factors are held constant, and cooling it off will decrease the pressure. The behavior of matter, particularly liquids and gases, under conditions of changeable temperature and pressure is a little complex.