The Air Around You

1
The Air Around You
2
Earths Atmosphere

• Earths atmosphere is the envelope of gasses that
  surround the planet.
• Nitrogen makes up 78 of our air
• Oxygen makes up 21 of our air
• The remaining 1 are called trace gasses.
• How many more times Nitrogen than Oxygen in our
  air?
• Read about nitrogen and oxygen on page 7-8 in
  your book and answer questions 4-8 in your notes.

3
Water Vapor

• Water in the form of a gas is called water vapor
• Water vapor is not the same as steam because
  steam is warm air with tiny droplets of water in
  it.

• What role does water vapor play in Earths
  weather?

4
How does Earths atmosphere make conditions on
Earth suitable for living things?

• Oxygen and other gases needed for life
• Constantly moving in and out of living things
• Warmth
• Liquid water
• Protects from radiation and meteoroid

5
Do the next page in your notes (pg. 50) on your
own as review. What you dont get done is
homework.

• When you are finished, brainstorm about air
  pressure in the graphic organizer on the next
  page of your notes (pg. 54). Then begin to read
  section two (Air Pressure).

6
Properties of Air

• Weight of the atmosphere is constantly pushing on
  your body
• Air has mass because it is composed of atoms and
  molecules.
• Because air has mass, it has density and pressure
• The more molecules in a given volume of air, the
  greater its density.

7
Cause and Effect

• If mass increases and volume stays the same then
  density increases
• If mass decreases and volume stays the same then
  density decreases
• If mass stays the same and volume decreases then
  density increases
• If mass stays the same and volume increases then
  density decreases

8
Measuring Air Pressure

• An instrument used to measure air pressure is a
  barometer.
• Mercury barometers have liquid mercury forced up
  a column when air pressure increases
• Aneroid barometer has no liquid and has thin
  walls and air tight metal chamber that bulges
  when air pressure increases.

9
Aneroid Barometer 1843- Lucien Vidie
Mercury Barometer 1644- Evangelista Torricelli
Read pp. 12-13
Aneroid without fluid
10
Units of Air Pressure

• Most weather reports for the general public use
  inches of mercury. For example, if the column of
  mercury in a mercury barometer is 30 inches high,
  the air pressure is 30 in.
• National Weather Service maps indicate air
  pressure in millibars. One inch of mercury is
  approximately 33.87 millibars.

11
Isobars are lines on maps that join places that
have the same air pressure.
12
Altitude

• Another word for elevation, or distance above sea
  level
• At the top of a mountain the air pressure is less
  than the air pressure at sea level.
• Air pressure decreases as altitude increases.
• As air pressure decreases, so does density.
• Read Altitude Affects Air Pressure on pg. 13 to
  answer why air pressure is greater at sea level
  than at the top of a mountain.

13
Altitude also affects density

• As you go up through the atmosphere the density
  of air decreases.
• The gas molecules that make up the atmosphere are
  farther apart at higher altitudes.
• If you were near the top of a tall mountain and
  began to run, you would run out of breath more
  quickly than at sea level. Why?
• The air contains 21 Oxygen at any level, but
  since the air is less dense at higher altitudes
  there are fewer oxygen molecules to breath in
  each cubic meter if air than at sea level.
• Explain why mountain climbers sometimes bring
  tanks of oxygen along with them on their climbs.

14
Do page 57 and 58 for homework
Do not give up on page 58! Be sure to read the
directions first. They will help you find the
right answers!