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Gas Pressure P

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A set of slides created to teach Gas Pressure P to learners at Bishops Diocesan College in Cape Town.

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Transcript of "Gas Pressure P "

1. 1. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Air Pressure Keith Warne
2. 2. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Air Pressure • Gas molecules move rapidly in all directions. • Collisions exert a force on objects and the container. • The number of collisions determines the total force being exerted. • Increasing number of collisions would INCREASE Pressure. The pressure is given by the AVERAGE FORCE PER UNIT AREA.
3. 3. Standard Atmospheric Pressure • The pressure that supports 760.0 mm of mercury is known as STANDARD ATMOSPHERIC PRESSURE or 1 ATMOSPHERE. (1 atm) taken at sea level. • Since liquid pressure can be found by P = gh  = density of liquid = 13 590 kg/m3 (mercury) g = gravitational field strength = 9.807 N/kg h = height = 0.7600 m p = gh = (13590)(0.76)(9.807) = 101 300 Pa Pa = 1atm H = 760mm 1 Pa = 1 N/m2 ATMOSPHERIC pressure SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY
4. 4. Water Barometer • The pressure that supports 760.0 mm of mercury is known as STANDARD ATMOSPHERIC PRESSURE or 1 ATMOSPHERE. (........................) taken at sea level. • What would the equivalent height of water be? • Since liquid pressure can be found by P = gh  = density of water = .................kg/m3 g = gravitational field strength = 9.807 N/kg h = height = ...........?? m p = gh ATMOSPHERIC pressure WATER!WATER! H = ?? m SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY
5. 5. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Atmospheres mm Hg kPa 1 760 100 2 ??? ??? 0.5 ??? ??? X ??? X ??? X ??? X ??? atm kPa Pressure Conversions
6. 6. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Aneroid Barometer • An aneroid barometer has a vacuum chamber that expands or contracts with changes in air pressure. • The expansion/contraction causes a series of levers to pull on a chain that is connected to a spindle. • The spindle turns and moves the needle attached to it on the dial, showing the air pressure. From World Book © 2002 World Book, Inc., 233 N. Michigan Avenue, Suite 2000, Chicago, IL 60601. All rights reserved. World Book illustration by Zorica Dabich
7. 7. HIGH PRESSURE HIGH PRESSURE HIGH PRESSURE Aneroid Barometer CHANGE LOW PRESSURE SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY
8. 8. Pressure Demonstrations - Plunger High Pressure If the plunger is forced down the air is forced out of the cavity. Low Pressure If the plunger is pulled up – the pressure inside the cavity is DECREASED so the atmospheric pressure on the outside is GREATER and it holds the plunger against the surface. Air escapes! SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY
9. 9. Heated air escapes replaced by STEAM Can crushing Experiment Water boils - atmospheric pressure balanced by steam inside. Steam condenses to water – no gas inside to balance atmospheric pressure – ATMOSPHERE CRUSHES CAN! WATER
10. 10. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Ball Pressure • A ball needs pressurized air inside it to enable it to bounce. • The higher the pressure the better (HIGHER) the ball will bounce. • If the atmospheric pressure increases a higher pressure will be needed in the ball.
11. 11. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Aerodynamics & Air Pressure
12. 12. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net + + + + + + + + + + ++ + + + Pumping air out of the jar causes the balloon to inflate!
13. 13. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLY For FULL presentation click HERE >> www.warnescience.net Hi - This is a SAMPLE presentation only. My FULL presentations, which contain loads more slides (with all the gaps filled in) as well as other resources, are freely available on my resource sharing website: www.warnescience.net (paste into your browser if link above does not work) Have a look and enjoy! Keith Warne
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