Earth Science
Chapter 15
Section 1
A. The Air Around You:
Weather is a condition of Earth’s atmosphere at a particular
time and place.
Earth’s atmosphere is the layer of gases that surrounds the
planet.
Earth’s atmosphere makes conditions on Earth suitable for
living things.
Living things constantly change the atmosphere.
The Earth’s atmosphere captures the sun’s energy, and holds
water in the vapor, liquid and solid states.
The atmosphere protects Earth from radiation and some
meteorites from space.
B. Composition of the Atmosphere:
Earth’s atmosphere is made up of nitrogen, oxygen, Argon,
carbon dioxide, water vapor and trace gases. Also solid
particles called
Aerosols.
Gases in Dry Air:
Nitrogen
78.08%
Oxygen
20.95%
Argon
0.93%
Carbon Dioxide
0.036%
Trace gases
less than 0.01%
Nitrogen is essential to living things.
Most living things cannot obtain nitrogen directly from the
air.
Bacteria convert nitrogen to nitrates.
Plants absorb the nitrates to make proteins.
Animals eat plants or other animals to obtain proteins.
This is known as the Nitrogen Cycle.
Oxygen is a diatomic molecule, it has two oxygen atoms
bonded together to make one oxygen molecule as it exists in
the atmosphere.
Oxygen is used in chemical processes such as burning and
oxidation (rust) and is a by-product of photosynthesis.
Ozone is a form of oxygen that has three oxygen atoms in
each molecule. Ozone can absorb ultraviolet radiation.
Carbon dioxide consists of one carbon atom and two oxygen
atoms.
Plants need carbon dioxide to produce food
Living things give off carbon dioxide as a waste product.
Burning fossil fuels give off carbon dioxide.
Carbon dioxide contributes to global warming because it
holds heat energy. This is known as an absorbing gas.
Other gases- less than .01% of trace gases
Water Vapor is water in the gaseous state or form.
Water also exists in the atmosphere as water droplets and ice
crystals that form clouds.
Droplets or ice crystals that fall from a cloud is known as
precipitation.
Particles (not gases)- The atmosphere contains aerosols or
liquid or solid particles such as dust, smoke, salt and other
chemicals.