The Atmosphere

The Atmosphere

Why is the atmosphere important?

•Earth’s atmosphere, or the layer of gases that surrounds the planet, is important for many reasons…

• The atmosphere contains oxygen and other gases that living things need.

• The atmosphere traps energy from the sun, which keeps Earth’s surface warm and Earth’s water in liquid form.

• The atmosphere protects Earth from dangerous radiation from the sun and meteoroids.

Atmosphere & Weather

• Atmosphere: the layer of gases that surrounds the Earth

• Weather: the condition of Earth’s atmosphere at any given time or place

What gases are in our atmosphere?

• •Nitrogen (N2) = 78%

  • Oxygen (O2) = 21%

  • Trace gases = 1%

    Argon

    Carbon dioxide

    Neon

    Methane

    Krypton

    Hydrogen

What else is in our atmosphere?

• Water vapor: gaseous water from evaporation and transpiration (1 tree gives off 40,000 gallons of water vapor in a year!)

• Solid particles: dust, smoke, pollen, salt, particles from car exhaust, burning and volcanic eruptions

What is carbon dioxide (CO₂)?

•Carbon dioxide: a molecule composed of two atoms of oxygen and one atom of carbon; a gas at room temperature

What are some sources of carbon dioxide (CO₂) in our atmosphere?

• All living things produce CO₂ through the process of respiration

• Burning fossil fuels releases extra CO₂ into the atmosphere

Greenhouse Effect

• The greenhouse effect is the process by which gases in the atmosphere absorb thermal energy and then radiate it back to Earth.

• Carbon dioxide and methane are two of the most abundant greenhouse gases. Both gases are produced by burning fossil fuels.

• Earth is able to maintain an ideal temperature to support life because of our atmosphere.

CFCs

• Chlorofluorocarbons (CFCs) are another type of greenhouse gas produced by refrigerants and industry. CFCs also deplete the ozone layer in the stratosphere.

• Water vapor is actually considered a greenhouse gas as it can hold in large amounts of heat.

The Ozone Layer

• Ozone: a form of oxygen with 3 atoms of oxygen (O₃)

• The ozone layer in the atmosphere absorbs harmful ultraviolet radiation from the sun

Properties of Air

• Some important properties of air include:

  –Air Pressure

  –Humidity

  –Altitude

  –Temperature

  –Density

Under Pressure

• Air Pressure: the weight of a column of air pushing down on an area

  –More dense air has higher air pressure than less dense air.

  –The weight of the column of air that pushes down on an area the size of a student desk is about the same as the weight of a school bus!

Measuring Air Pressure

• Barometer : An instrument used to measure air pressure

• Units of Air Pressure:

  –Inches of Mercury

  –Millibars

Mercury Barometer

• A mercury barometer consists of a glass tube open at the bottom end and partially filled with mercury.

• In weather reports, air pressure is usually given in inches of mercury.

Altitude

• Altitude: the distance above sea level, also known as elevation or height

  –Air pressure decreases as altitude increases.

  –As air pressure decreases, so does density.

  –Sea-level air has the weight of the whole atmosphere pressing on it, so air pressure is highest at sea level and much lower at the tops of mountains.

So, why doesn't air pressure crush everything?

• The reason is that the molecules in air push in all directions- down, up, and sideways. 

• So, the air pushing down on top of an object is balanced by the air pushing up on the bottom of the object.

Quiz time!

Do you have your notes?

Multiple Choice

What is the most abundant gas in our atmosphere?

• Oxygen

• Methane

• Nitrogen

• Helium

Multiple Select

What are some TRACE gases in our atmosphere (choose 3)

• Nitrogen

• Oxygen

• Carbon Dioxide

• Methane

• Hydrogen

Multiple Choice

What is ozone?

• liquid oxygen

• oxygen molecule with 3 atoms of oxygen instead of 2

• a form of rust

• a type of oil

Multiple Select

What are some of the solid particles in air? (choose 4)

• dust

• smoke

• pollen

• sand

• volcanic eruptions

Multiple Choice

Why would there be more water vapor in a tropical rain forest than in a desert?

• a) the climate is wet in a rain forest and a lot of water would evaporate

• b) there would be a lot of transpiration from the trees

• both a and b