The Atmosphere Notes 7th Grade Science
Chapter 1 Section 1 The Air Around You
Weather is the condition of Earth’s atmosphere at a particular time and place.
Atmosphere is the envelope of gases that surrounds the planet.
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.
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.
Other gases in the atmosphere: Ozone is a form of oxygen that has three oxygen atoms in each molecule.
Carbon Dioxide is important because plants need it to survive. When fuels such as coal and gasoline are burned, they release carbon dioxide.
Water vapor is water in the form of gas. Trace gases are the remaining gases, only small amounts of them are present.
Other Gases Percentage by Volume Argon .93 Carbon Dioxide .038 Neon .0018 Helium .00052 Methane .00015 Krypton .00011 Hydrogen .00005
In addition to gases, the atmosphere contains other particles. *dust *smoke *salt *pollen *other chemicals
Video Clip on The Atmosphere
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
Chapter 1 Section 2 Air Pressure
Air has mass, it also has other properties, including density and pressure. Density = Mass Volume Pressure = force pushing on an area
Who is feeling the most pressure here and why?
Which layer of the atmosphere do you think has the greatest amount of pressure?
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!
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.
If this is true, how are we not being squished?
Air pressure is the result of the weight of a column of air pushing down on an area.
Bill Nye Video Clip
A barometer is an instrument that is used to measure air pressure.
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
Aneroid Barometer - measures changes in air pressure without using a liquid
Units of Air Pressure Inches of Mercury (30 in) Millibars (1,016 mb)
Altitude, or elevation, is the distance above sea level, the average level of the surface of the oceans.
Air pressure decreases as altitude increases Air pressure decreases as altitude increases. As air pressure decreases, so does density.
Air Pressure Video Clip