Chemistry of-the-atmosphere-3-v2.0

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What goes into our atmosphere?
How do human activities affect the air we breathe?

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Why is the atmosphere important?
80% of atmospheric gases
are in the 15km closest to
Earth. This is a very thin
layer compared to the
Earth’s diameter, which is
12,756 kilometres.
The Earth is different to the
other planets in our solar
system because it has an
atmosphere that can
support life.
The atmosphere is an
envelope of different gases
(air) surrounding Earth.

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What is the atmosphere made of?
The gases that make up the atmosphere are present in the
following amounts:
about 78%
is nitrogen
about 21%
is oxygen
the remaining 1% is
mostly argon (0.93%)
with some carbon
dioxide (0.035%),
varying amounts of
water vapour and
trace amounts
of other gases

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Does Earth’s atmosphere change?
About 3,500 million years ago,
the atmosphere on Earth
would have been similar to the
atmosphere on Mars today.
What theories are used to
explain how the Earth’s
atmosphere changed?
It would have contained large
quantities of carbon dioxide, but
not much oxygen or nitrogen.
The current composition of the air has been roughly the
same for nearly 200 million years but the amounts of different
gases have changed over time.

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The history of the atmosphere

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Evolving atmosphere

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What is air pollution?
Air pollution is the
presence of substances in
the air that are harmful to
health or the environment.
It can be easy to spot air
pollution in cities, but its
effects are not limited to
urban areas because air
circulates freely all over
the world.
Air pollution can cause the destruction of forests, death of
fish in lakes and premature death in humans.
How does air pollution cause so many problems?

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What causes air pollution?
The most common pollutants found in air are:
nitrogen monoxide (NO)
How are these molecules produced and how do they
carbon dioxide (CO2)
sulfur dioxide (SO2)
nitrogen dioxide (NO2)
carbon monoxide (CO)
carbon particulates
affect the environment?

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Causes and effects of air pollutants

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How is carbon dioxide produced?
The element carbon is found in all living things
and moves through the environment in a chain
of reactions known as the carbon cycle.
In this cycle, the chemical reactions that take
place during respiration and burning fossil
fuels produce carbon dioxide.
Carbon dioxide is an important atmospheric
gas as it prevents heat radiation produced
by the Earth from escaping into space.
This is the greenhouse effect, which
makes the Earth warm enough for life.
However, increased levels of carbon
dioxide in the atmosphere could cause
dramatic changes to the Earth’s climate.

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How do fossil fuels cause air pollution?
When fossil fuels are burnt fully in oxygen, the chemical
reaction that occurs is called complete combustion.
carbon dioxidefossil fuels oxygen water++ 
 Fossil fuels often contain sulfur and
so the pollutant sulfur dioxide can
be produced during combustion.
 Increased carbon dioxide levels
due to human activities are thought
to be connected to global warming.
 Combustion also produces carbon
particulate matter.
The problems with burning fossil fuels include:

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What is incomplete combustion?
If there is not enough oxygen present when fossil fuels are
burned, incomplete combustion occurs. This reaction
produces carbon and carbon monoxide gas.
Carbon monoxide gas is extremely harmful to human health
because it stops blood from carrying oxygen.
 Faulty gas appliances, such as heating boilers,
can produce carbon monoxide. This gas is
colourless and odourless, so boilers need to
be checked for safety at least once a year.
 Burning wood can also produce carbon
monoxide. In areas where forests have
been cleared and burned, carbon monoxide
levels can reach dangerously high levels.

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What is acid rain?
Acid rain is rain, or precipitation, with a pH of 5.6 or lower. It
is caused by the pollutants sulfur dioxide and nitric oxides.
The term ‘acid rain’ was first used
by the Scottish scientist, Robert
Angus Smith, in the 19th century.
He conducted air quality research
in Manchester, one of the first
industrialized cities in the world.
Acid rain causes millions of pounds
worth of damage to buildings in the
UK each year.
It is also harmful to the environment
and can destroy forest habitats.

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Causes and effects of acid rain

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Summary of air pollutants
What are the causes and effects of these air pollutants?
pollutant cause
carbon dioxide
nitric oxides
carbon
monoxide
sulfur dioxide
particulates
high temperature
combustion
combustion and
respiration
incomplete
combustion
burning wood
and fossil fuels
burning coal
effect
lowers blood’s ability
to carry oxygen
acid rain and smog
adds to the
greenhouse effect
acid rain
deposits as soot
and lung damage

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Air pollution activity

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How does air pollution affect health?
Normally, pollution levels in the UK are
not high enough to cause problems to
people’s health.
People who know they are sensitive to
pollutants are advised to take precautions
when air pollution levels are high,
Weather reports often include warnings
about high air pollution levels. Why is this?
high
However, high pollution levels have
been shown to irritate existing heart and
respiratory problems. Air pollution can
even cause premature death in the
vulnerable or elderly.
low
moderate
such as not to exercise outside.

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Ozone is formed when nitrogen oxides and volatile organic
What is smog?
Smog is a mixture of air
pollutants and particulates
that is sometimes found in
the lower levels of the
atmosphere.
Smog is more common in summer because hot weather
acts as a catalyst in the formation of smog components.
It can reach dangerous
levels in built-up areas.
compounds combine with oxygen.
A large part of smog is ground level ozone (O3). This is a
highly toxic gas that can damage the lungs.

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Does air pollution cause asthma?
Asthma is a chronic respiratory condition
that affects the airways and can cause
shortness of breath and wheezing.
The UK has one of the highest rates of
asthma in the world: more than one million
people aged under 16 have asthma and, in
2004, 1,389 people died of asthma.
Air pollutants can make asthma worse in
people who already have the condition,
by triggering asthma attacks.
However, currently there is not enough evidence to support
the theory that air pollution causes people to have asthma.
Often, asthma is an hereditary condition.

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Why should we control pollution?
For example, severe smog in
London caused the premature
death of 12,000 people in 1952.
Human actions can cause or
reduce air pollution, which is
not just a current problem.
Most of the smog was formed
by high levels of particulates
in the air, caused by burning
wood and coal for heating.
The Clean Air Act of 1956 created smoke-free zones in cities.
Power plants were moved to rural areas, reducing city smog.
How else have human actions improved the atmosphere?

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Is there a hole in the ozone layer?
In the 1980s, scientists discovered that ozone was being
destroyed by the chlorofluorocarbons (CFCs) widely used in
aerosols and refrigerators. CFCs can stay in the environment
for 50 years, destroying ozone long after they are produced.
The ozone layer in the upper atmosphere filters UV radiation.
However, international regulations
to reduce CFC emissions may be
helping to repair the ozone layer.
Studies in 2006 showed that the
hole in the ozone layer is not
getting bigger. It is possible that if
CFCs remain banned the ozone
layer could return to normal levels.

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How can air pollution be reduced?
Today, the combustion of fossil fuels is a major source of air
pollution and so controlling their use is important in reducing
pollution. This can be done in three key ways:
 Reduce the amount of fossil fuels used
by taking simple steps such as changing to
energy efficient light bulbs or cycling
instead of using a car.
 Increase the efficiency of motor
vehicle engines and power plants so
that less fossil fuels are required.
 Use chemical reactions to remove
the most harmful pollutants from motor
vehicle and power plant emissions.

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How can coal be made cleaner?
Sulfur dioxide emissions from coal can be reduced in two
ways: by removing sulfur from the coal before combustion
or by filtering the emissions produced by combustion.
A process called flue
gas desulfurization is
used to filter emissions.
processed
flue gas
flue gas
gypsum
limestone
and water
Sulfur dioxide in the
flue gas is removed
by reacting it with
limestone and water.
This forms calcium
sulfate, also known
as gypsum, which can
be used in construction.

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How can vehicle pollution be reduced?
A catalytic converter is a device
that is fitted to the exhaust pipe of
a car to clean up exhaust fumes.
This structure maximizes contact between the exhaust
fumes and the metal catalyst to change the pollutants
from combustion into less harmful substances.
The inside of the converter has a
honeycomb structure, covered in
a metal catalyst, such as
platinum or palladium.
+ oxygen carbon dioxide
carbon
monoxide
nitric oxides nitrogen oxygen+


+

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Potent pollutants

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Glossary (1/2)
 acid rain – Rain (or precipitation) with a pH of 5.6 or less.
 air pollution – The presence of substances in the air that
are harmful to health or the environment.
 asthma – A respiratory condition affecting the airways.
 atmosphere – The envelope of gases surrounding the
Earth.
 carbon monoxide – A gas produced during incomplete
combustion that reduces the ability of blood to carry oxygen.
 catalytic converter – A device fitted to a car exhaust to
change polluting exhaust gases into less harmful substances.

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Glossary (2/2)
 incomplete combustion – The burning of fossil fuels
with insufficient oxygen. This produces carbon monoxide.
 nitric oxides – Compounds of nitrogen and oxygen
that can cause acid rain and smog.
 particulate – A fine dust or particle found in the air.
 sulfur dioxide – A gas produced by the combustion of
fossil fuels that can cause acid rain.
 smog – A mixture of particulates and air pollutants that
can form in the lower levels of the atmosphere.

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Anagrams

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Multiple-choice quiz