Air Pressure

1. Air Pressure Mrs. Wharton’s Science Class

2. Air • Air consists of atoms and molecules therefore it has mass. • Because air has mass it also have other properties such as density and pressure. • Air has weight • Air molecules are in constant motion and are affected by gravity. • The force of this motion causes air pressure.

3. Density and Air Pressure • Density- the amount of mass in a given volume of air. • Pressure- the force pushing on an area or surface. • Air Pressure- is the result of weight of a column of air pushing down on an area. • The molecules in air push in all directions so it does not crush objects.

4. Air Pressure • Air pressure varies slightly over the earth’s surface, and variations are responsible for the weather. • Low pressure is associated with storms, tornadoes and hurricanes • High pressure is associated with clear and dry conditions.

5. Air Pressure • Air pressure changes with elevation • As you move up into the atmosphere, the air molecules are further apart • As you move down into the atmosphere, the air molecules move closer together.

6. Barometers • Barometer- an instrument that is used to measure air pressure • Mercury Barometer- glass tube partially filled with mercury. • Aneroid Barometer- most used in homes.

7. Altitude and Properties of Air • As altitude increases air pressure decreases • As altitude decreases air pressure increases • As pressure decreases, density decreases • As pressure increases, density increases