13/01/2014 Air Quality W Richards The Weald School (OCR 21 st Century)

10/04/23

Air QualityAir Quality

W Richards

The Weald School

(OCR 21st Century)

10/04/23

Section C1.1 – Our airSection C1.1 – Our air

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The Earth’s AtmosphereThe Earth’s Atmosphere

Carbon dioxide, water vapour

Oxygen Nitrogen Noble gases

Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2

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AirAirAir is a mixture of different gases consisting of small molecules with large spaces between them:

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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day

Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere

Carbondioxide

Methane Ammonia Oxygen Nitrogen Others

Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2

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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day

Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere

Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans.

Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.

Green plants evolve which take in CO2 and give out oxygen. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. Methane and ammonia react with the oxygen and nitrogen is released.

10/04/2310/04/23Carbon dioxide in the Carbon dioxide in the atmosphereatmosphereThe amount of CO2 in the atmosphere is affected by 3

things: 1) Geological activity moves carbonate rocks deep into the Earth and they release ______ _______ into the atmosphere during volcanic activity.

2) When fossil fuels are burned the carbon contained in them reacts with _____ to form CO2.

3) Increased CO2 in the atmosphere causes a reaction between it and _______. These reactions do not remove ALL of the new CO2 so the greenhouse effect is still getting _______!

Words – oxygen, seawater, carbon dioxide, worse

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PollutionPollutionWhat happens to pollution?

Carbon dioxide causes global warming but some of it can be removed by plants (photosynthesis) or reactions with seawater.

Sulfur dioxide and nitrogen dioxide cause acid rain which damages trees and buildings.

Particulates (like in smog) can make buildings dirty and worsen breathing difficulties.

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PollutionPollutionHumans pollute the Earth in a number of ways:

Pollutant Harmful to...

Why?

Carbon dioxide Environment

Nitrogen oxides Environment + humans

Sulfur dioxide Environment

Particulates (e.g. Smoke)

Environment + humans

Carbon monoxide Humans

A greenhouse gas that causes global warming

Causes acid rain and makes asthma/breathing problems worseCauses acid rain

Makes buildings dirty and makes asthma worse

Displaces oxygen in red blood cells that can result in death

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Section C1.2 – PollutionSection C1.2 – Pollution

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FuelsFuelsFuels are substances that can be used to release useful amounts of energy when they burn, e.g.

Oil GasWood Coal

These fuels are called “fossil fuels” and are described as being “non-

renewable”. The main element in these fuels is Carbon.

10/04/23Burning HydrocarbonsBurning Hydrocarbons

Burning hydrocarbons will produce water, carbon dioxide and energy:

C

H

H

H

HO

O

OO

OH H

OH H

CO

O

Methane Oxygen+ Water+Carbon dioxide

In this reaction the hydrocarbon is “oxidised” (“oxidised” means that oxygen has been added and it’s the opposite of reduced).

Oil, petrol and diesel are all examples of HYDROCARBONS. A hydrocarbon is a compound made up of carbon and hydrogen.

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More information on oxygenMore information on oxygen

Fuels need oxygen to burn. The more oxygen they have, the quicker they will burn. This is the principle behind oxy-acetylene torches:

10/04/23Other products of burning Other products of burning fuelsfuels

Sulphur dioxide:

Nitrogen monoxide:

Nitrogen monoxide can be further oxidised to make nitrogen dioxide (Nitrogen monoxide and dioxide are jointly referred to as NOx):

SO

O

Sulphur dioxide

SO

O

Sulphur Oxygen+

Nitrogen monoxid

e

NO

NO

Oxygen+

OO

Nitrogen

NN

OO

Oxygen+Nitrogen monoxid

e

NO

NO

Nitrogen dioxide

N OO

N OO

10/04/2310/04/23Conservation of mass in Conservation of mass in reactionsreactions

In any reaction the total mass of products is the same as the total mass of the reactants

Example 1 – Magnesium oxide and hydrochloric acid

Mg OH Cl

Mg ClCl

HH OH Cl

1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms

Also 1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms

C

H

H

H

HO

O

OO

OH H

OH H

CO

O

Example 2 – Burning methane

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Incomplete CombustionIncomplete CombustionAs well as producing carbon monoxide, incomplete combustion can also produce soot:

Little oxygen:

CC

H

H

H

H

Methane

OO

Oxygen+

OH H

OH H

Water+Carbon

“Soot”

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Burning Fossil FuelsBurning Fossil FuelsBurning fossil fuels like oil and coal causes pollution.

Oil contains carbon:

C

H

H

H

HO

O

OO

OH H

OH H

CO

O

Carbon dioxide is a “greenhouse gas” – it helps cause global warming

Coal contains carbon, sulfur and other particles:

sulfur + oxygen sulfur dioxide

Sulfur dioxide causes acid rain. Other particles can cause “global dimming” – sunlight is absorbed by the particles in the atmosphere.

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Summary of pollutantsSummary of pollutants

C

Carbon

CO

O

Carbon dioxide

Nitrogen monoxid

e

NO

Nitrogen dioxide

O NO

SO

O

Sulfur dioxide

OH H

Water

C

Carbon monoxid

e

O

Each of the following chemicals is a product of burning fossil fuels. For each one summarise how it is made and what harm it causes:

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C1.3 Improving Air QualityC1.3 Improving Air Quality

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Removing PollutionRemoving PollutionThere are many ways pollution can be reduced:

• Use less electricity/central heating

• Remove toxic chemicals before or after they are burnt

• Use alternative energy sources, e.g. wind power

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Removing SulfurRemoving Sulfur10/04/23

Sulfur dioxide is clearly bad for the environment so it’s a good idea to remove as much sulfur as possible:

Vehicles can remove sulfur from fuels before they are burned.

Power stations can remove sulfur dioxide from waste gases after combustion.

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Wet ScrubbingWet Scrubbing“Wet scrubbing” is a term used to describe the removal of sulfur dioxide and other particles using seawater or an alkaline spray:Step 1 – the dirty gas is fed in through the top.

Step 2 – the “scrubbing liquid” (seawater or alkaline spray) is fed in through the side.

Step 3 – the mixture is fed into a cyclone area where the slurry is collected at the bottom of the device.

10/04/23Reducing Pollution from Reducing Pollution from vehiclesvehiclesA number of suggestions:

1) Buy a new, smaller, more efficient car

2) Use legal limits (e.g. An MOT) to enforce lower emissions3) Use low sulfur fuels or convert your car to run on biodiesel

4) Make sure your car has a catalytic converter:

5) Use the train or a bus!

Carbon monoxide + oxygen carbon dioxide

Nitrogen monoxide + carbon monoxide nitrogen + carbon monoxide

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Alternative FuelsAlternative FuelsCar makers are currently researching two alternatives for petrol and diesel-powered cars. What are the advantages and disadvantages of each?

1) Electric cars

Advantages:

Disadvantages:

2) Biofuel cars

Advantages:

Disadvantages:

10/04/23Making choices about Making choices about pollutionpollution

Choices concerning fighting pollution can be made on many levels:

1) International

e.g. The Kyoto protocol in 1997

2) National

e.g. Car tax system, subsidies for greener technology

3) Local

e.g. Recycling schemes, transport, congestion charges

4) Personal

e.g. Recycling, individual travel, reducing energy usage in the home etc