Water and Air Pressure

1. Water and Air Pressure

2. Pressure • The amount of force applied to a given area. • Why do ears ‘pop’? • Answer: When the air pressure outside changes, the air pressure inside your middle ear has to adjust, resulting in the popping sound..

4. Air Pressure • Air Pressure is a measure of the force of the air pressing down on the earth’s surface

5. Air Pressurecan vary at any particular point on the Earth depending on the density of the air • Density = mass / volume

6. Changes in Pressure • Layers of air in the Earth’s atmosphere are higher than 160 km above the Earth’s surface. • Being closer to the surface, we experience air pressure as a result of all the air particles being pulled toward the Earth by gravity.

7. Changes in Air Pressure • You experience less air pressure as you travel to higher altitudes because of the fewer layers above us and air is less dense.

8. Density = Mass / Volume  Warm air is less dense than cool air. Warm air rises. Cool air sinks.  Air at high altitudes is less dense than air at lower altitudes.

9. Pressure in Depth-Water Pressure • The weight of the water at the upper part of the pool presses down on the deeper levels of the pool, resulting in greater pressure at that point. • (Hence, your ears feel a lot of pressure deeper in the waters) • Pressure does not include the total amount of fluid present only the depth of the fluid.

10. Density • Water is about 1000 times more dense than air. • If you measure the same volume of water and air, water has more mass and weighs more than air. • Water exerts a greater pressure than air pressure.

11. Pressure and Fluid Flow • Fluid will always want to move from an area of high pressure to an area of low pressure • When drinking a juice box, the straw pulls from an area of high pressure (juice box) to an area of lower pressure (mouth)

12. Pressure and Temperature • When temperature increases, particles more faster and strike the walls of their container more often and with more force • When enough force is exerted and the volume of the container cannot increase anymore an explosion can occur

13. Compression • Compression is a decrease in volume caused by a force • Gasses can experience compressibility because the particles in a gas are so far apart that they have room to move closer to one another • Materials in a liquid state are incompressible • Video

14. Compressed Bottle • Compressibility is the ability to be compressed, or forced to have less volume • Gas can be compressed • We pushed the particles closer together through force and reducing the volume of the bottle • When enough force is exerted and the volume of the container cannot increase anymore an explosion can occur • Water vapour (gas) is in air • Water was inside the bottle and when the bottle opened pressure was released and returned to its gaseous form (i.e. what looked like smoke coming out of the bottle)

15. Title: Activity 1. Inverted Cup Date: Feb. 2010 Summary:

16. Inverted Cup When cup is completely filled with water, no air is left in cup, thus no air pressure. The inverted cup can therefore hold water up because the air pressure is working against the underside of the cup. cardboard Air Pressure There is higher air pressure outside pushing upward than the inside of cup pushing downward.