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The Pressure is On!


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Investigation 4-3

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The Pressure is On!

  1. 1. Heating Earth The Pressure is On! 4-3
  2. 2. Atmosphere <ul><li>What have we discovered about air so far? </li></ul><ul><ul><li>Is matter - has mass & occupies space </li></ul></ul><ul><ul><li>Is mixture of gases - mostly nitrogen & oxygen </li></ul></ul><ul><ul><li>Made of individual nitrogen & oxygen molecules flying through space </li></ul></ul><ul><ul><li>Can heat up & cool down </li></ul></ul><ul><ul><li>Gets denser as it cools, less dense as it warms </li></ul></ul>
  3. 3. Atmosphere <ul><li>Planet Earth is completely surrounded by a thin layer of air. </li></ul><ul><ul><li>Called the atmosphere </li></ul></ul><ul><ul><li>Extends up about 300 miles above Earth’s surface </li></ul></ul><ul><ul><li>Most of the air is in first 9 miles </li></ul></ul>
  4. 4. Investigating Air <ul><li>Use syringe and plastic tube to find out more about air. </li></ul><ul><li>Answer the following questions: </li></ul><ul><ul><li>What happens to air in the syringe when you push and pull on the plunger? </li></ul></ul><ul><ul><li>What can air do? </li></ul></ul>
  5. 5. Air & Syringes <ul><li>Record your observations on notebook sheet </li></ul><ul><li>Try investigations on sheet - record observations and any questions </li></ul><ul><li>What observations did you make? </li></ul><ul><li>What questions do you have? </li></ul>
  6. 6. Air Observations <ul><li>When you clamp the tube closed and push the plunger down, what happens to the air? </li></ul><ul><li>Is there more air, less air, or the same amount of air in the syringe when the air is pushed into a smaller space? </li></ul><ul><ul><li>How do you know? </li></ul></ul><ul><li>What happens when you let go of the plunger after pushing it down?* </li></ul><ul><li>What do you think happens to the air when it is pushed into a smaller space? </li></ul><ul><li>What happens to push the plunger back out when you release the plunger? </li></ul>
  7. 7. Compression and Pressure <ul><li>When you push on the plunger, the air is forced into a smaller space. </li></ul><ul><ul><li>The air is compressed </li></ul></ul><ul><ul><li>Same amount of air is still in the syringe when compressed </li></ul></ul><ul><li>Compressed air pushes back with a force equal to the force compressing it. </li></ul><ul><ul><li>Pushing force is called pressure </li></ul></ul><ul><ul><li>If force on plunger is released, the pressure in the compressed air will push the plunger out </li></ul></ul>
  8. 8. Molecular Model of Air <ul><li>Air is made of tiny particles </li></ul><ul><ul><li>Called molecules </li></ul></ul><ul><ul><li>Made mostly of Nitrogen & Oxygen molecules </li></ul></ul><ul><ul><li>So tiny you can’t see them </li></ul></ul><ul><ul><li>Free to move around - not attached </li></ul></ul><ul><ul><li>Lots of space between molecules in gases </li></ul></ul>
  9. 9. Bottle Demonstration <ul><li>What do you think will happen to the bottle when I suck on the tube? </li></ul><ul><li>Why did the bottle get crumpled? What caused the bottle to collapse?* </li></ul><ul><li>Bottle collapsed and crumpled for the same reason a syringe plunger moves in and out “by itself” when connected to a second syringe. </li></ul><ul><li>What causes plunger in syringe #2 to slide in and out when you push and pull the plunger in the syringe #1? </li></ul>
  10. 10. Atmospheric Pressure <ul><li>Syringe has a little bit of air trapped between rubber tip of plunger and clamp. </li></ul><ul><ul><li>Air molecules are flying around & banging into each other, sides of syringe, & plunger tip </li></ul></ul><ul><ul><li>Air molecules outside the syringe also flying around; banging into each other, outside of syringe, & back side of syringe plunger. </li></ul></ul><ul><ul><li>Banging produces pressure </li></ul></ul><ul><ul><li>Air inside syring pushes on inside of syringe; air outside syringe pushes on outside of syringe </li></ul></ul>
  11. 11. Atmospheric Pressure <ul><li>Applying force to plunger to pull it out. </li></ul><ul><ul><li>Release plunger, it slides back into barrel by itself </li></ul></ul><ul><ul><li>What makes the plunger go back into the barrel where it started? </li></ul></ul><ul><li>Atmospheric Pressure! </li></ul><ul><ul><li>Pull plunger = larger space but same number of molecules </li></ul></ul><ul><ul><li>Pressure is less inside syringe </li></ul></ul><ul><ul><li>Pressure is greater outside syringe </li></ul></ul><ul><ul><li>Plunger is pulled back until pressure is equal both inside and outside </li></ul></ul>
  12. 12. Atmospheric Pressure <ul><li>Atmospheric pressure is pressure due to the mass of air pulled to Earth by gravity. </li></ul><ul><ul><li>Same in all directions - upward, downward, & to the sides </li></ul></ul><ul><ul><li>Air is pushing on every side of you & everything else on Earth’s surface with equal force </li></ul></ul><ul><li>Complete Atmospheric Pressure at Work sheet </li></ul>
  13. 13. Vocabulary <ul><li>Compress </li></ul><ul><ul><li>squeeze (air) molecules into a smaller volume (space) </li></ul></ul><ul><li>Pressure </li></ul><ul><ul><li>force or push casued by moving molecules </li></ul></ul><ul><li>Atmosphere </li></ul><ul><ul><li>layer of air around Earth </li></ul></ul><ul><li>Atmospheric pressure </li></ul><ul><ul><li>Force applied in all directions by the air in Earth’s atmosphere </li></ul></ul>
  14. 14. Content <ul><li>What happens when air is pushed into a smaller space? </li></ul><ul><ul><li>Air molecules move closer together, resulting in compressed air </li></ul></ul><ul><li>What causes atmospheric pressure? </li></ul><ul><ul><li>The weight of air </li></ul></ul><ul><li>Homework: Read The Pressure is On! & Summary: Heating Earth and answer questions; I-check 4 on February 28th (14 & 12) or March 1st (15) </li></ul>
  15. 15. The Pressure is On! <ul><li>What is atmospheric pressure and what causes it? </li></ul><ul><li>Is atmospheric pressure higher on a mountaintop or at sea level? </li></ul><ul><li>Why did the bag of chips puff up over Tioga Pass? </li></ul><ul><li>Why was the empty water bottle crushed when they returned to San Francisco? </li></ul>
  16. 16. Summary: Heating Earth <ul><li>What causes uneven heating of Earth’s surface? </li></ul><ul><li>How does uneven heating of Earth’s surface results in convection currents? </li></ul><ul><li>What is atmospheric pressure and what causes it? </li></ul><ul><li>In what direction does atmospheric pressure push? </li></ul>