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Air Pressure Activities A.Inverted Glass In your notebook: B.Stop the Leak C.Collapsing Can D.Fastest Drinker 1. Diagram of set-up 2. Description of results 3. Explanation/principle involved Air Pressure Air Pressure • Air Pressure is a measure of the force of the air pressing down on the earth’s surface Air Pressure can vary at any particular point on the Earth depending on the density of the air Density = mass / volume Title: Activity 1. Inverted Cup Challenge: Date: Feb. 2010 1. Fill a cup with water. 2. 3. Cover the cup with an index card. Invert the cup. What happened? Does the water spill out of the cup? Explain (using concepts on pressure) Results and Explanation: Summary: Inverted Cup cardboard Air Pressure 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. There is higher air pressure outside pushing upward than the inside of cup pushing downward. Title: Activity 2. Stop the Leak Challenge: Solution: Results and Explanation: Summary: Date: Feb. 2010 How can you stop the leak in this soda can? Stop the Leak By plugging one of the holes, the air inside stays the same because outside air is prevented from coming into the hole. The higher water volume inside causes a decrease in pressure. Thus, outside air pressure (which is greater) pushes against the water and prevents it from flowing out. Air cannot go in Liquid cannot flow out Air pressure outside of can is greater than air pressure inside. Title: Activity 3. Collapsing Can Challenge: Date: Feb. 2010 How can cause a can to collapse? Solution: Results and Explanation: Summary: Explain the principle behind the collapsing can. Collapsing Can Before heating, the can was filled with water and air. By boiling the water, the liquid changed into water vapor The water vapor or steam pushed the air that was inside, out of the can. In closing off the can, air is prevented from going back to the can. Cooling (water in basin) condenses water vapor back to water. All the vapor which took up space inside the can turned into a few drops of water, which take up less space. Pressure inside can drops allowing outside air pressure to push on the can and crush it. Title: Activity 3. Straw drinking race Challenge: Who can drink the fastest? Regular straw Results and Explanation: Summary: Date: Feb. 2010 Modified straw Explain the principle behind straw drinking. When you drink liquid through a straw, is it accurate to say the liquid is sucked up the straw or pushed up the straw? Straw Drinking Race The higher pressure in outside air pushes the liquid up the straw in our mouth Sucking creates a partial vacuum or a lower pressure in straw above the liquid that we drink The student with the leaky straw cannot create a vacuum above the liquid, so the liquid is not pushed up. 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. Factors that affect Pressure Air Temperature Water Vapor Elevation TEMPERATURE AND AIR PRESSURE HEAT LESS AIR PRESSURE Molecules move faster Move apart, become fewer and weigh less HIGH TEMPERATURE, LOW AIR PRESSURE LOW TEMPERATURE, HIGH AIR PRESSURE AMOUNT OF WATER VAPOR consists of air and water molecules More water vapor means less air molecules LOW AIR PRESSURE DRY AIR = HIGH AIR PRESSURE Factors Affecting Air Pressure FACTOR Density Density Temperature Temperature Water Vapor Water Vapor Altitude Altitude Increase/Decrease Air Pressure Measuring Air Pressure Types of Barometer Air Pressure is Mercury Barometer measured by an instrument called Aneroid Barometer Air pressure increases, column of mercury rises Air pressure decreases, column of mercury drops Air Pressure & Weather High pressure generally means fair weather Air mass in upper atmosphere No clouds Layer of Air Warm, moist air cannot rise Low pressure generally means cloudy, rainy weather Air masses move apart Warm air rises, clouds form QUESTIONS – use your knowledge of air pressure to explain the following situations A falling barometer is followed by several days of rainy weather. Some people find it hard to breathe at high altitudes. A rising barometer indicates a spell of cool dry weather.