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