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Air Pressure Powerpoint

8th Grade Science

leenior
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Air Pressure Powerpoint

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  1. Air Pressure Winds & Isobars

  2. 01 Air Pressure & Winds

  3. Outcome Essential Question I Can: Explain how air pressure and wind result in changes to weather conditions. What causes weather to change from day to day or even from hour to hour? Changes in weather are primarily the result of a change in temperature, air pressure, and humidity in the atmosphere. When any of these three variables experience a substantial change, it can lead to a complete change in weather conditions. Weather is ultimately caused by temperature differences due to variations in solar energy input.  These temperature differences cause pressure variations in the atmosphere.  The wind blows to try and correct these imbalances in pressure.  Regions of low and high pressure moving through an area cause changes in weather as different air masses pass by.

  4. The answer is simple. Your ear popping is a sign that the AIR PRESSURE has changed. The air near the surface of the Earth is very dense, or more compact, due to all the air molecules above pushing down. When you travel on a plane or to an area higher in elevation the air is less dense (less compact). This change in air pressure causes the air trapped in your ear to put pressure on your ear drum causing the Why do your ears pop on an airplane, in an elevator, or on a drive through the mountains? POP!

  5. Air pressureis the weight of the air pressing on an object. High Pressure = Greater Force Low Pressure = Less Force What is air pressure? In the image to the right, where would the air pressure be the greatest? Why? Answer: Air pressure is greatest at the surface of the earth because there is more air above to push down on you.

  6. The Air Out There How can we prove that the air in the room is exerting a force? Air Pressure Stations The Spill Test Volcano Bottle Hole in One Balloon Trick DEMO #1 DEMO #2 DEMO #3 DEMO #4 DATA TABLE

  7. The Air Out There Air Pressure Stations Stations

  8. Demonstration #1: The Spill Test DIRECTIONS https://www.youtube.com/watch?v=65T4ReLkjCg • Fill a small plastic cup one-third with water. • Cover the entire mouth of the cup with an index card. • Holding the card in place, take the cup to the sink and turn it upside down. Remove your hand from underneath. • What happens? Record our observations in your data table. DATA TABLE Stations

  9. Spill Test Explanation • When you first turn the cup upside down, the pressure of the air inside the cup and the air pressure outside the cup are equal. If you look closely, however, you’ll notice that just a little water leaks out between the card and the cup. This happens because the force of gravity naturally pulls down on the water. When some of the water escapes, this causes the volume of air (the space above the water inside the cup) to increase slightly. Even though the amount of air above the water stays the same, the volume occupied by the air is now greater and the air pressure inside the cup decreases. The pressure of the air outside the cup is now greater than the pressure inside the cup and the card stays in place. All of this is possible because the water creates an airtight seal between the rim of the cup and the card. • When the seal is broken (even a tiny bit), air enters into the cup, equalizes the pressure, and gravity pushes the water out. Poking a thumbtack-size hole in the cup allows air to seep into the cup from the outside. The pressure of the air molecules both inside and outside the cup stays the same, gravity takes over, the card falls, and the water spills. • https://www.youtube.com/watch?v=M3ep-Bx_3yY

  10. Demonstration #2: Volcano Bottle DIRECTIONS • Fill an empty soda bottle half full of water. • Take a long straw and insert it into the opening of the bottle. • Wrap a lump of modeling clay around the straw to form a seal between straw and the mouth of the bottle. • Blow hard into the straw and stand back. Record your observations in your data table. • https://www.youtube.com/watch?v=9bYku0t-RMc&list=PLCA9B7D3D7031D919&index=10 DATA TABLE Stations

  11. Demonstration #3: Hole in One DIRECTIONS • Take an empty water or soda bottle and lay it down horizontally on a table. • Roll a piece of paper towel into a small ball about half the size of the opening. • Try to blow the ball into the opening of the bottle. **DO NOT cheat! You are not allowed to place the ball on the outer edge of the opening of the bottle ** • What happens? Record your observations in your data table. • https://www.youtube.com/watch?time_continue=46&v=OPu0_ADO6FQ&feature=emb_logo DATA TABLE Stations

  12. Hole in One Explained • Air has a lower pressure when it's moving more quickly. As you blow into the mouth of the bottle the air is moving fastest - so is at the lowest pressure. Inside the bottle, the air is moving more slowly - so a higher pressure. As the pressure is higher inside the bottle than in the mouth this pushes the paper out! • More simply, air pressure near the mouth of the bottle drops and greater air pressure inside the bottle pushes the paper ball out.

  13. Demonstration #4: Balloon Trick DIRECTIONS • Blow up two balloons and attach a piece of string to each. • Hold one balloon by the string in each hand and position the two balloons so that they are at your nose level and 6 inches apart from each other. • Blow hard into the space between the balloons. • What happens? Record your observations in your data table. • https://www.youtube.com/watch?v=3fWSTXDQ8eE DATA TABLE Stations

  14. Balloon Trick Explained • Bernoulli’s Principle – Fast moving air exerts lower pressure on any object than static air. • Air is flown between the balloons. Air on the farther sides is static. Pressure between the balloons is lower than the pressure on the farther sides of the balloons. • This pushes the balloons inside making the stick to each other. • Another example: When strong winds blow, air moves at a high speed, which reduces the pressure on rooftops. The air inside the hut remains at high pressure and then starts pushing the roof. If the roof is not fixed properly, it will be blown up and fly away in the strong wind.

  15. STEMScopes PREDICTING WEATHER Engage - Hook Forecasting Weather https://app.acceleratelearning.com/scopes/13725/elements/659454

  16. How Powerful Is the Air? • What is air made of? Matter • Does air have mass and volume? Yes • What force keeps the atmosphere around Earth? Gravity • How far does the atmosphere extend from Earth’s surface? 600 km or 375 miles • Does the mass of the atmosphere affect us? Yes, it pushes down on us. • What is this called? Air pressure • How does our body handle air pressure? Human bodies are able to handle air pressure, although the only time you might notice it is when your ears pop as they adjust to a change in atmospheric pressure. Your body self-regulates to the different weights of the air above you. • What happens when air is heated? The molecules contained in it expand, causing the air to become less dense and rise. • What happens when air is cooled? The molecules contained in it contract, causing the air to become more dense and sink. • What happens to the air pressure when air is cooled? The air pressure decreases.

  17. Air Pressure Can Crush Experiment • Fill an empty 12-oz soda can with approximately 30 mL of water. • Place the soda can directly on a hot plate or electric burner, and wait for the water inside the can to begin to boil and evaporate. You will see steam coming out of the opening. • Use the beaker tongs and quickly but safely lift the soda can off the burner. • Immediately immerse the soda can upside down into a large bowl of ice water. https://www.youtube.com/watch?v=xg5NiOwf_Zw

  18. What Happened? Remember that even though air is invisible, it still takes up space and has weight. When the air in the can was heated, the air inside the can rose and some escaped. As the water in the can was heated, it evaporated, became water vapor, and escaped as steam. It fills much of the newly created space left by the escaping air. When the can was placed in the tub of ice water, the water vapor instantly condensed back into liquid water. For just a second or two, the can was filled with only a little water and air, and a lot of empty space! The air pressure at sea level is 14.7 pounds per square inch, and that force was pressing on the outside of the can, but very little air is pushing back in all directions from the inside. This greater air pressure on the outside caused the can to be crushed by pushing on it from the outside.

  19. Warm Air Rises - The Spinning Paper Plate Experiment • Predict what will happen when you hang the spiral over the hot plate after it has been turned on. • Turn on the hot plate and allow it to warm for about 1 minute. • Holding the spiral by the long end of the pin, place it over the hot plate. • Do not allow the paper to touch the burner. 1. What is a convection current? A circular movement of fluids caused by the rising of hotter, less dense fluid and the falling of cooler, more dense fluid. 2. Do you think we might have convection currents in the classroom? Yes, think about how it is warmer near the ceiling. 3. What type of energy transfer is going on? Thermal energy transfer https://www.youtube.com/watch?v=4cOMushj7w8

  20. What Happened? Explanation: • The burner heated the surrounding air. Heating air causes the air molecules to travel farther apart, thereby making the air less dense. Less dense air will always rise above dense air. • As the warm, lighter, air rises upwards the paper spiral begins to spin. The process keeps working because the cooler surrounding air keeps coming towards the light and warming up. This is a simple demonstration of convection currents that exist in thunderstorms and ocean currents.

  21. Condensation, Ice and Plastic Bag Experiment How Is Condensation Related to Humidity? • What happens to the outside of a cold soda can that is placed on a table for a few minutes? It gets wet. • Where does this liquid come from? The water vapor in the air. • Fill two clear plastic cups with room temperature water and ice cubes. • Quickly place one of the cups in a gallon-size plastic bag, squeeze as much air out of the bag as possible, and then close the bag securely. • Allow the cups to sit undisturbed for 5–10 minutes. • After the 5–10 minutes, have the students observe the cups https://www.youtube.com/watch?v=bOoMCiv5FYE&feature=emb_title

  22. Air Pressure and Temperature Have you ever wondered what makes a hot air balloon go up? How do they make it come down? When air is heated, the molecules of gas spread away from each other. This means that the air pressuredecreases. The heated, less dense air RISES creating a LOW pressure area. When air is cooled, the molecules of gas move closer together and push down more. This means that the air pressureincreases. The cooled, more dense air sinks creating a HIGH pressure area.

  23. High vs. Low Comparison

  24. Air Pressure & Wind • When warm air risesin a LOW pressure area, cool sinking air in a HIGH pressure area comes in to replace it. • This movement of air is called WIND. • The larger the temperature difference between the LOW and HIGH, the stronger the wind. WIND

  25. Air Pressure & Wind Land Breeze vs. Sea Breeze Winds are named after where they come from… Sea breezes come from the sea Land breezes come from the land Cooler air sinks Cooler air sinks Clouds form Clouds form Cooler sea breeze Cooler land breeze Warmer air rises Warmer air rises warm land cool sea cool land warm sea

  26. Global Winds • Global winds are named after the direction they COME FROM (ex. Prevailing Westerlies come from the west) • Due to the temperature differences at different latitudes and the rotation of the Earth (Coriolis Effect), global winds blow in a regular, constant pattern • Remember, air moves from a HIGH to LOW pressure area • Warm air rises at the equator and moves toward the poles. At the poles, the cooler air sinks and moves back toward the equator.

  27. Summary

  28. 02 Air Pressure & Isobars

  29. Phenomena Outcome Essential Question What do spaghetti models show us? I Can: Predict weather from data collected for air pressure changes. How can you use air pressure readings to predict the weather?

  30. I Spy Weather Maps You have one minute to identify as many weather map symbols as you can!

  31. Isobars are lines connecting points of equal atmospheric pressure that can be used to identify high pressure areas and low pressure areas. Typically isobars look like circles. Atmospheric pressure is often measured in millibars,a unit of air pressure in the metric systemequal to or slightly less than 1/1000th of a standard atmosphere. When an isobar of lower pressure is located inside an isobar of higher pressure it forms a low pressure system. When an isobar of higher pressure is located inside an isobar of lower pressure it forms a high pressure system. Low pressuresystems usually bring precipitation with wind blowing counterclockwise around the low. High pressure systems usually bring dry weather and clear skies with wind blowing clockwise around the high. High Pressure, Low Pressure & Isobars • Use the atmospheric pressure map of the United States to create Isobars and label them as High pressure or Low pressure systems.

  32. Isobars are usually drawn for every 4 millibars (or increments of pressure) using 1000 millibars as your starting point. These lines should have values of 1000, 1004, 1008, 1012, 996, 992, 988, 984, etc.. • The high numbers on the map are the high pressure systems and the low numbers are the low pressure systems. • In a high pressure system, winds revolve around it in a clockwise direction. Wind direction is created by the sinking of cooler, drier air. • In a low pressure system, winds revolve around it in a counter- clockwise direction. Wind direction is created by the rising of warm, moist air. • In most cases, these air pressure systems move in a west to east direction.

  33. The pressure is 1008 millibars all along this line Lines close together show a big difference in air pressure. Expect strong winds here. Lines are far apart where the air pressure is almost even. Expect calm air or light breezes near this high.

  34. Map Activity First, watch this video https://www.youtube.com/watch?v=N5rJ1yWk4IU Using SCRIBBLE begin drawing from the 1024 millibars pressure over Salt Lake City (see on map) and connect to all the other 1024 millibars in the area to create a circle. Repeat this process with the 1020 millibars creating two circles around Salt Lake City. 01 02 Now move to the Eastern side of the country. Find similar millibars and create three isobars (hint: it will look like three concentric circles). Check your isobars with your teacher 03 04

  35. High Pressure, Low Pressure & Isobars • Label the center of the high pressure area with a large BLUE “H”. • Label the center of the low pressure area with a large RED “L”. • Draw arrows around the “H” on your map to indicate the correct wind direction. • Draw arrows around the “L” on your map to indicate the correct wind direction. • Shade, in green, the state(s) you would expect to see rain or snow. • Shade, in yellow, the state(s) you would expect to see clear skies.

  36. High Pressure, Low Pressure & Isobars https://www.youtube.com/watch?v=cXVybr7L9II Help with drawing:

  37. Other Educational Videos & Resources • Determining Direction of Wind on Weather Map https://www.youtube.com/watch?v=_MBIFofeFKw • What Causes Weather To Change, Change So Quickly, And Can It Be Predicted? https://ownyourweather.com/what-causes-weather-to-change-so-quickly/ Please keep this slide for attribution

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