Air Pressure (David Choi)
Title: Living at the Bottom of an Ocean of Air
Principle(s) Investigated:
• Dispel misconceptions about air
• Air has weight
• Air takes up space
• Universal Gravitation causes increased air pressure the close you are to earth.
• Atmospheric Pressure at sea level- 1kg per square cm - 14.7 pounds per square inch
• Atmospheric Pressure can be used to predict weather
Investigation and Experimentation
7. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations.
Materials:
10 inch Baloons.
Empty soda bottles
Empty orange juice container with a small hole in it.
Procedure:
1. Divide Class into 5 groups.
2. Pass out 2 liter bottle and a balloon.
3. Insert a deflated balloon into a plastic soda bottle.
4. Stretch the mouth piece to fit over the mouth of the bottle.
5. Ask Again – Is it possible to blow this balloon inside this bottle?
Use Socratic method & have Students figure it out by themselves.
Don’t Tell them the answer just ask the right questions.
A. Yes in two different ways.
6. First team to figure it out and succeed raise your hands.
Use competition to further engage everyone in collaborative learning.
7. Balloon will not be able to inflate because there is air trapped in the bottle around the balloon. You must either squeeze out some of the air in the bottle before placing the balloon over the mouth of the bottle. Or you can puncture a hole in the bottle to let the air out as you blow into the balloon that is in the bottle.
8. Teacher demonstrates that that you can indeed blow up a balloon in the 2 liter bottle using a bottle with a hole in it.
9. If you plug the hole with your finger the balloon will not deflate.
10. Ask the Class to write in the quickwrite why the air does not escape from the balloon.
11. Pass out Clear Orange Juice bottles that have holes in them.
Orange juice bottles are more rigid and work better than 2 liter bottles for this part of the experiment.
Place the balloon over the mouth of the container.
Ask them to Write in the quickwrite.
Can you blow up this balloon inside the bottle without blowing on the balloon?
12. Why does the balloon inflate when you suck air out of the hole?
Student prior knowledge: What prior concepts do students need to understand this activity?
1. Air has weight.
2. Air takes up space
3. The Earth's atmosphere exerts a pressure that decreases with distance above Earth's surface and that ant any point it exerts this pressure equally in all directions.
Evangelista Torricelli- Renaissance Mathematician, who’s experiments discovered Atmospheric Pressure.
“We live submerged at the bottom of an ocean of Air”
Explanation:
Because air has mass, the universal law of gravitation affects it. We literally "live under an ocean of air" where air pressure increases the closer we are to the earths surface. The earth's gravity pulls air molecules toward the center of the earth. The closer we are to the earth's surface the greater the air pressure. Air is denser at the surface of the earth and the higher we go in the atmosphere, there is less air. Air pressure is a powerful force as we will explain below.
Questions & Answers: Give three thought-provoking questions and provide detailed answers.
1. Why am I not crushed by the atmospheric pressure?
Atmospheric Pressure at sea level- 1 ATM = 1kg per square cm or 14.7 pounds per square inch
Humans adults have 14 to 18 sq feet of skin.
16 feet as the average
2304 square inches (16x12x12)
2304 x 14.7 pounds = 33,868 pounds of pressure on you body.
Metric ton= 2205 lb
33,868/2205lb = 15.36 Metric tons
Now you know why you are so tired after a long day?
If you are under so much pressure, Why are we not crushed?
Counter intuitive – We don’t feel the pressure.
We don’t feel the pressure because the Air pressure is balanced by the air inside our body.
The air pressure inside our body keeps us from being crushed by the air pressure outside our body.
2. Why doesn't the air escape from the balloon when there is nothing to stop the air from escaping?
(Balloon is not tied & nothing is covering the hole you blew on to inflate the balloon)
The Air pressure from the outside of the bottle pushes on the balloon keeping it inflated because there is not enough air inside the bottle.
3. Why does the balloon inflate when you suck air out of the hole of the bottle?
You are creating vacuums when you suck air out of the hole. The air pressure becomes unbalanced and the air pressure outside the bottle becomes stronger than the air pressure inside the bottle. Therefore the outside air wants to come inside the bottle. As the air comes inside the bottle, it blows up the ballon inside the bottle.
Applications to Everyday Life:
1. Straw
When you use a straw you create a vacuums with your mouth and the air pressure pushing on the surface of the water pushes the liquid up the straw.
2. Pilots use altitude readings that are converted from atmospheric pressure readings.
3. Barometer & Weather
a Barometer measures air pressure. The open end of the barometer pushes the Mercury up the tube as the air pressure increases.
Air pressure readings are used to predict weather patterns.
Low pressure Warmer weather, storms & rain.
High pressure Cooler temperatures but clear good weather.
High Pressure – Air Slowly descending over a large area (few hundred miles)
As air descends – it warms which inhibits formation of clouds.
Generally associated with good weather.
Low Pressure system – Air rises and cools.
As air air cools the humidity in it begins to condense into tiny drops of water.
Or if it is cold enough into tiny ice crystals.
If there is enough water or ice, rain or snow begin to fall.
Low pressure is associated with bad weather.
Northern Hemisphere.
High Pressure -Air descending flows out in a clockwise spiral
Low Pressure Air rises in a counterclockwise spiral.
Photographs: