Behavior of Gases

Behavior of Gases

How are Pressure & Volume Related

Gases, Pressure, and the Atmosphere

What’s in Earth’s atmosphere (nitrogen)

●Nitrogen (N₂) gas makes up 78% of Earth’s atmosphere

●Released by volcanoes and decaying organisms

●Protein contains nitrogen

●Nitrogen is converted into nitrates (NO₃) by nitrogen-fixing bacteria in
the soil

●Plants absorb nitrates from the soil and use them to make proteins

●We eat plants or meat to obtain these proteins

Gases, Pressure, and the Atmosphere

What’s in Earth’s atmosphere (oxygen)

●The second most abundant gas is oxygen (O₂), which makes up 21% of Earth’s
atmosphere

●Carried by the Blood Hemoglobin on the RED BLOOD CELLS & used to produce
ENERGY

●0.93% is made up of Argon

●0.04% is made up of carbon dioxide

●The rest is tiny amounts of neon, helium, methane, krypton, and hydrogen, which we
call trace gases

Multiple Choice

Earth's current atmosphere is

• 78% nitrogen, 21% oxygen, 0.93% argon and 0.04% carbon dioxide

• 78% oxygen, 21%nitrogen, 0.9% argon, 0.037% carbon dioxide
• 78% nitrogen, 21% argon, 1% oxygen
• 78% oxygen, 21% nitrogen, 1% carbon dioxide

Multiple Choice

What gas makes up 21% of Earth's Atmosphere?

• Nitrogen

• Oxygen

• Ozone

• None of the Above

Why our Atmosphere Exists

Earth’s Gravity Holds all these gases down

Mercury is too small to hold atmospheric gases

Gases, Pressure, and the Atmosphere

Atmospheres of Earth, Venus, and Mars
●An atmosphere is a layer of gases surrounding a
planet

●The atmospheres of Venus, Earth, and Mars were
formed in similar ways

●Life uses photosynthesis to obtain energy from the
Sun

●This process breaks down carbon dioxide, uses
carbon to build the organism, and releases oxygen
into the air

Gases, Pressure, and the Atmosphere

Atmospheres of Earth, Venus, and Mars (cont.)
●

Organisms DIE and DECOMPOSE, some of the
carbon from their bodies gets released as
carbon dioxide back into the air

●

Some CARBON from these organisms stay on
the ground and is stored inside the ground

Gases, Pressure, and the Atmosphere

Atmospheres of Earth, Venus, and Mars (cont.)
●

Earth stores Carbon

●

Some marine organisms use the carbon dioxide
dissolved in the ocean to form shells of calcium
carbonate

●

When these organisms die they settle at the bottom
of the ocean floor and this carbon is stored

●

Fossil fuels also store this carbon as oil, coal, and
natural gas

Multiple Choice

Earth's atmosphere is important to living things because it

• contains dust and other particles
• is very thin compared to the size of Earth
• provides all the gases that living things need to survive
• maintains a constant relative humidity

Multiple Choice

When you breathe in, you breathe in mostly which gas?

• oxygen
• carbon dioxide
• nitrogen
• argon

Multiple Choice

TRUE or FALSE?
All of the carbon in existence is continually recycled in the carbon cycle.

• True
• False

Multiple Choice

When humans burn fossil fuels, most of the carbon quickly enters the                       as carbon dioxide.

• Water
• Atmosphere
• Sun
• Air

Multiple Choice

Which one of these does not add CO2 to the atmosphere?

• cooking with gas
• planting trees
• burning wood
• riding in a bus

Multiple Choice

Where did the nitrogen in Earth’s atmosphere come from?

• Plants

• Volcanoes and decaying organisms

• Burning fossil fuel

• Helicopters

Multiple Choice

What was the Earth's early atmosphere like ?

• Similar to Mars and Venus. A large amount of carbon dioxide,little or no oxygen small amounts of other gases, such as ammonia and methane

• Similar to Mercury. A large amount of oxygen, sodium and hydrogen.

• Similar to Jupiter. A large amount of hydrogen and helium.

• Similar to Pluto. A large amount of nitrogen.

Gases, Pressure, and the Atmosphere

What is atmospheric pressure?

●The pressure of air molecules in the atmosphere is a result of the weight of a column of
air pressing down on an area (air pressing down on you)

●Atmospheric pressure is a measurement of the force of air molecules per unit of area
in the atmosphere at a given altitude.

The more air above you, the MORE AIR PRESSURE

Gases, Pressure, and the Atmosphere

What is atmospheric pressure?

●At sea level, the weight of the column of air above a person is
about 9,800 newtons (N), which is 2,200 pounds

●This is equal to the weight of a small car

●Why aren’t we crushed by this pressure?

●There is air inside our bodies that is pushing out with the same
pressure, so the forces are balanced

●Our skeletons are designed to withstand the pressure of our
environment as well

Multiple Choice

The pressure exerted by the weight of air is called

• atmospheric pressure

• atmospheric temperature

• altitude

• density

Gases, Pressure, and the Atmosphere

Barometers and units of pressure

●Atmospheric pressure is measured with an instrument
called a barometer

●old barometer used mercury

●It consists of a tube that is sealed at one end and
partially filled with mercury

●The open end of the tube faces down into a dish of
mercury

●As air presses down on the mercury in the dish, it forces
the liquid in the tube to rise

Gases, Pressure, and the Atmosphere

Aneroid Barometers

●Mercury barometers have a downside: Mercury is a poisonous
liquid, and it creates unhealthy vapors

●Most barometers we use today have an airtight cylinder made of
thin metal

●The walls of the cylinder are squeezed inward when the
atmospheric pressure is high

●At lower pressures, the walls bulge out

●A dial attached to the cylinder moves as the cylinder changes
shape, this measures the pressure

Gases, Pressure, and the Atmosphere

Atmospheric pressure and altitude
●

Atmospheric pressure decreases with
more altitude

●

This is because you have less air
molecules above you forcing their
weight on you as you go higher

●

At Sea Level is where you would the
most of air molecules above you

Multiple Choice

Which of the following measures air pressure?

• Thermometer
• Barometer
• Wind Vane
• Hygrometer

Gases, Pressure, and the Atmosphere

Atmospheric pressure and altitude

●The graph shows that as altitude increases the atmospheric
pressure decreases rapidly (exponentially)

Multiple Choice

Atmospheric pressure increases (gets bigger) as altitude increases (the higher up you go)

• true

• false

Multiple Choice

Which of the following is the correct composition of Earth’s modern atmosphere?

• 78% oxygen, 21% nitrogen, 1% other

• 78% nitrogen, 21% oxygen, 1% other

• 50% oxygen, 50% nitrogen

• 75% oxygen, 25% nitrogen

Multiple Choice

Which two gases make up 99% of gases in the atmosphere?

• Nitrogen and Oxygen

• Nitrogen and Carbon Dioxide

• Oxygen and Methane

• Ozone and Argon

Multiple Choice

which layer of the atmosphere has the most pressure?

• thermosphere

• mesosphere

• stratosphere

• troposphere

Multiple Choice

Which layer of the atmosphere has the most mass? (80% of the mass actually!)

• stratosphere

• troposphere

• mesosphere

• thermosphere