1. The Atmosphere Notes
7th Grade Science

2. Chapter 1
Section 1
The Air Around You

3. Weather is the condition of Earth’s atmosphere at a particular time and place.

4. Atmosphere is the envelope of gases that surrounds the planet.

5. Earth’s atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids.

6. Nitrogen is the most abundant gas in the atmosphere, making up about three fourths of the air.
Oxygen is the second most abundant gas, it makes up less than one fourth of the volume.

7. Other gases in the atmosphere:
Ozone is a form of oxygen that has three oxygen atoms in each molecule.

9. Carbon Dioxide is important because plants need it to survive.
When fuels such as coal and gasoline are burned, they release carbon dioxide.

10. Water vapor is water in the form of gas.
Trace gases are the remaining gases, only small amounts of them are present.

11. Other Gases
Percentage by Volume
Argon
.93
Carbon Dioxide
.038
Neon
.0018
Helium
.00052
Methane
.00015
Krypton
.00011
Hydrogen
.00005

12. In addition to gases, the atmosphere contains other particles.
*dust
*smoke
*salt
*pollen
*other chemicals

13. Video Clip on The Atmosphere

14. Earth’s atmosphere makes conditions on Earth suitable for living things.
1. contains oxygen and other gases
2. traps energy from the sun
3. protects living things from dangerous radiation
4. prevents Earth’s surface from being hit by most meteoroids

15. Chapter 1
Section 2
Air Pressure

16. Air has mass, it also has other properties, including density and pressure.
Density = Mass
Volume
Pressure = force pushing on an area

17. Who is feeling the most pressure here and why?

18. Which layer of the atmosphere do you think has the greatest amount of pressure?

19. Click on the balloon to find out!
What happens to the pressure as your travel up through the layers of the atmosphere?
Click on the balloon to find out!

20. Earth’s gravity pulls gases toward the surface
Earth’s gravity pulls gases toward the surface. The weight of the gases press down. Molecules nearest to Earth’s surface are closer together.
This makes air pressure higher in the lowest level.

21. If this is true, how are we not being squished?

22. Air pressure is the result of the weight of a column of air pushing down on an area.

23. Bill Nye Video Clip

24. A barometer is an instrument that is used to measure air pressure.

25. Mercury Barometer - measures changes in air pressure, consisting of a glass tube partially filled with mercury, with its open end resting in a dish of mercury

26. Aneroid Barometer - measures changes in air pressure without using a liquid

27. Units of Air Pressure
Inches of Mercury (30 in)
Millibars (1,016 mb)

28. Altitude, or elevation, is the distance above sea level, the average level of the surface of the oceans.

29. Air pressure decreases as altitude increases
Air pressure decreases as altitude increases. As air pressure decreases, so does density.

30. Air Pressure Video Clip