OCR 21st Century Science - CHEMISTRY C1

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C1- Air Quality
Pollutants in the Air
Pollutants are chemicals. They can harm the environment and our health.
Human actions such as burning fossil fuels release pollutants into the atmosphere, e.g. from power
stations or cars.
Pollutants can harm us indirectly. For example, acid rain makes rivers too acidic for organisms to
survive. This affects our food chain and natural resources, e.g. trees.
Pollutant Harmful to... Why?
Carbon dioxide Environment Traps heat in the Earth's
atmosphere (it is a
greenhouse gas).
Nitrogen oxides Environment Causes acid rain
Humans Causes breathing problems
and can make asthma worse.
Sulfur dioxide Environment Causes acid rain
Particulates (small Environment Makes buildings dirty
particles of solids, e.g. Humans Can make asthma and lung
carbon) infections worse if inhaled.
Carbon monoxide Humans Prevents the blood from
carrying oxygen, which can
be fatal
The Atmosphere
The Earth is surrounded by a thin layer of gases called the atmosphere.
The atmosphere contains...
About 78% nitrogen, 21% oxygen, 1%argon and other noble gases and small amounts of water
vapour, carbon dioxide and other gases.
Measuring Pollutants
It's possible to measure concentrations of pollutants in the air in ppb (parts per billion) or ppm (parts
per million). For example, a sulfur dioxide concentration of 16ppb means that in every one billion
molecules of air, 16 molecules will be sulfur dioxide.

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Pollution Data
Data can test a theory or an explanation,
Carbon monoxide (CO) is an example of a pollutant caused by humans. Concentrations are likely to
be higher in populated areas, e.g. cities.
The following data was collected in two places on the same day with a CO metre:
Time City Centre Concentration Country Park
9.00am 5.2 0.2
10.00am 4.9 0.1
11.00am 5.0 0.1
12.00pm 2.6 0.0
1.00pm 4.8 0.1
Measurements like this vary because variables like the volumes of traffic, affect concentrations.…read more

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The mean CO concentration in the city is significantly higher than in the country park. This supports
the theory that CO is a pollutant caused by human activity.
There's a real difference between the mean CO concentrations in the city and the park. This is
because the difference between the mean values is greater than the range of each set of data.
If the difference between the values had been smaller than the range then there would have
been no real difference.…read more

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Incomplete combustion
Incomplete combustion occurs when fuel is burned and there's not enough oxygen. Depending on
the amount of oxygen present, carbon particulates or carbon monoxide may be produced.
Incomplete combustion occurs in car engines. Exhaust emissions contain carbon particulates and
carbon monoxide as well as carbon dioxide. Coal can contain sulfur, so sulfur dioxide is released when
it's burned.
During the combustion of fuels, high temperatures, e.g. in a car engine, can cause nitrogen to
react with oxygen. This produces nitrogen monoxide (NO).…read more

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In some volunteers the skin became red and inflamed, indicating allergic reaction. The study showed
that people with pollen allergy also had hay fever and those who didn't have pollen allergy didn't get
hay fever.
This provided stronger evidence of a link between pollen and hay fever.
Repeated skin tests always produced the same results, which proved the tests were reliable.
Asthma is another condition linked to air quality. However, this example is more complicated.…read more

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In 1997 an international meeting about climate change in Kyoto, Japan, set targets to lower emissions
for individual countries. Each country's government must take appropriate measures to meet its
National choices
Government rules and regulations include:
Legal limits for exhausts emissions, enforced by MOT tests. Compulsory catalytic converters.
Subsidies or reduced taxes for companies who use `cleaner' fuels. Introducing a tax system that
encourages you to buy smaller cars. Encouraging investment in non-polluting renewable energy.
These laws impact on science and industry.…read more



really good thanks

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