What are the properties of gases?

Gases have three characteristic properties:

1. They are easy to compress.

2. They expand to fill their containers.

3. They take up much more space than the liquids or solids from which they are formed.

There is an important difference between gas pressure and other pressure examples. The pressure exerted by a woman in high heels or a 70,000 pound truck is directional. A truck, for example, exerts all its pressure on the surface under its wheels. On the contrary, the gas pressure is the same in all directions. To demonstrate this, we can fill a glass cylinder with water and cover the glass plate on top of the cylinder. When we turn the cylinder over, the plate does not fall to the floor because the air pressure outside the cylinder being pressed against the bottom of the plate is greater than the pressure exerted by the water in the cylinder pushing the plate.