What is Pressure?

Pressure is force per unit area. But in a gas what is creating this force? Every gas contains thousands of molecules and if the gas is in contact with any surface, those molecules are constantly hitting that surface. Each molecule has a mass and an acceleration to create a force.

                                        

What are the units of pressure?

1 Pa= 1 N/m^2 = 10^-5 bar

1 millibar = 100 Pa