States of Matter (Book)

Pressure is defined as the amount of force pushing against a given area. How much pressure a gas exerts depends on the amount of gas. The more gas particles there are, the greater the pressure.

You usually cannot feel it, but air has pressure. The gases in Earth’s atmosphere exert pressure against everything they contact. The atmosphere rises high above Earth’s surface. It contains a huge number of individual gas particles. As a result, the pressure of the tower of air above a given spot on Earth’s surface is substantial. If you were standing at sea level, the amount of force would be equal to 10.14 Newtons per square centimeter (14.7 pounds per square inch). This is illustrated in Figure below.