Page: 513, 1. Nitrogen is removed from the air mainly by the action of nitrogen-fixing. Bacteria

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1 Warm-up Page: 513, 1. Nitrogen is removed from the air mainly by the action of nitrogen-fixing. Bacteria Page: 514, 2. and plants produce large quantities of oxygen in a process called. Land & ocean, photosythisis Page: 514, 3. Moist air can contain as much as water Vapor. 4%

2 Warm-up quiz 1. Earth s most important external energy source is the F is the point of on the Fahrenheit scale. 3. The atmosphere helps regulate the of the Earth s surface 4. The atmosphere carries various kinds of particles such as and. 5. Moist air can contain as much as water Vapor Name 5 gases that are found in our atmosphere

3 Warm-up Page: 515, 1. How long can tiny particles of materials remain suspended in the atmosphere? months or years Page: 516, 2. Earth gravity keeps of the total atmosphere within of its surface. 99%, 32 km Page: 517, 3. Meteorologist use main types of to measure air pressure. Two, barometers

4 Objectives: SWBAT From demonstration understand air has pressure Explain how air pressure occurs Average air pressure at sea level = approximately 15 lbs./inch² Name a factor that increases and decreases air pressure Understand it is a vital when predicting weather

5 Activities Warm-ups Demo vacuum pup Notes/discussion Worksheet review atmosphere 1-4

6 Today s class is all about AIR PRESSURE. It s all around us all the time, It s important in weather prediction, But we rarely feel it or even think about it.

7 AIR PRESSURE The weight of earth s atmosphere

8 19-2 Air Pressure Air pressure is a force that is the result of the weight of air pushing down on an area.

9 This is the atmosphere; thinner higher up, thicker lower down

10 Air is thinner here. There are more air molecules lower down. Air is thicker here

11 The amount of air pressure depends on the density of the air, which is affected by three factors: elevation, temperature the amount of water vapor

12 Think of the atmosphere as an ocean of gases: At sea level, we are at the bottom

13 The more water is over you, the Greater the water pressure

14 Less Pressure More Pressure

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16 Imagine a stack of books. Which book has more weight on it, the second book from the top or the book on the bottom?

17 If the atmosphere is an ocean of air, think of ourselves as lobsters that are walking around on the bottom of this ocean.

18 Are there any creatures that swim in this ocean of air (like fish)?

19 How about these?

20 Our Atmosphere is like this, the more air is above you, the greater the Air Pressure

21 Continued The lower you are in the atmosphere, the more air is above you, and so the greater the Air Pressure is.

22 Air at the top of the atmosphere has less air pressing on it, and thus has lower air pressure.

23 Where is air pressure greatest? Where is it least? Station A, Station B, Station C;

24 Air Pressure at sea level is almost 15 pounds per square inch p.s.i It pushes in all directions!

25 Because the pull of gravity is not as strong at higher altitudes, the air molecules are farther apart (less dense) and exert less pressure on each other.

26 When objects are closer together, they create heat by friction. When air is dense, the molecules bump into each other more, which causes an increase in temperature. Warmer molecules move faster, which causes the air molecules spread apart and become less dense

27 After all, if you are hanging out with friends and it s hot out, do you want to be right next to them, or farther away?

28 Air that contains a lot of water vapor is less dense than drier air because water vapor molecules have less mass than nitrogen or oxygen molecules do.

29 Meteorologists measure atmospheric pressure by using an instrument called a barometer.

30 There are two kinds of barometers, a mercury barometer and an aneroid barometer. Mercury Barometer Aneroid Barometer

31 On weather maps, meteorologists connect places that have the same barometric reading with lines. These lines are called isobars

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33 Fill in the missing spaces Factor Increase or Decrease Causes Air Pressure to Density Temperature decrease increase Water vapor decrease Elevation increase

34 Air Pressure Demonstrations: Write down: 1. What happens, 2. Why it happens.

35 Demonstrations: A. The Magdeburg Hemispheres

36 A. The SPHERE. What force holds it together? How strong is this force?

37 The famous Magdeburg experiment reenacted. Air pressure holds the two sides of the sphere together

38 This week saw the 350th anniversary of the vacuum pump. Otto von Guericke (born 1602, died 1686) is a famous physicist and in 1646 was one of the 4 mayors of Magdeburg (Germany, only about 120 miles ENE of here). He invented a primitive vacuum pump in Then 350 years ago this week he performed the famous experiment-cum-demonstration of the force of air pressure. He had constructed two copper hemispheres and ground their flanges plane. The two hemispheres were then held together whilst he pumped the air out (to about a 90% vacuum). Atmospheric pressure then holds the evacuated hemispheres together. He then had two teams each of 8 heavy carthorses pull in opposite directions with all their might. Still they failed to separate the two copper hemispheres (for safety's sake, so as not to injure any successful horses, the two halves were loosely chained together too, with about 6 inches of play). When he opened the air valve, the halves fell apart with ease. This famous experiment is being reenacted in period costume to celebrate the 350th anniversary, so it was neat to see an historic experiment being done. See photo above. After the show, scientific curiosity having got the better of me, I got a chance to measure the diameter of the sphere, and so (assuming only a 90% vacuum) was able to calculate the force needed for the horses to pull the halves apart. A whopping 2.4 ton pull is needed!

39 B. The SUCTION cup. Why is it not really suction that holds it to a flat surface?

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43 What happens? Why? C. The BALLOON

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45 D. WATER What did it do? Why? Did it get hot?

46 E. MARSHMALLOW What happened? Why?

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50 F. SHAVING CREAM What happened? Why?

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53 If air pressure is so strong Why can t we feel it?

54 We have air pressure inside us pushing out.

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56 What would happen if a person were suddenly put somewhere where there is no air pressure like outer space? - Internal organs would rupture, - Bodily fluids would vaporize,

57 Your body would dry up and shrivel like a piece of beef jerky.

58 I had a person sized vacuum chamber a few years ago..

59 This is a former student who volunteered to go into the vacuum chamber.

60 Remember the Movie, TOTAL RECALL? What happened to the man who was put into the Martian atmosphere where air pressure is so Low?

61 Air Pressure is too Low!

62 The first Barometer

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65 Fewer air molecules = lower pressure More air molecules = higher pressure

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69 Cool down 1. If you drop a hammer and a feather on the moon which one hits the ground 1 st? They both fall at the same rate. -There is no air resistance to slow the feather 2. Why do your ears pop when you go up a mountain, or fly in an airplane? To equalize the pressure, less pressure outside you head the inside making your ears pop

70 Cool down 1. What is the instrument used to measure air pressure? barometer 2. What kind of air pressure brings bad weather? low pressure