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12/27/14 Air Quality Air Quality W Richards The Weald School (OCR 21 st Century)

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12/27/14

Air QualityAir Quality

W Richards

The Weald School

(OCR 21st Century)

12/27/14Section C1.1 – Our airSection C1.1 – Our air

12/27/14The 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

12/27/14AirAirAir is a mixture of different gases consisting of small molecules with large spaces between them:

12/27/1412/27/14

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

Evolution of the EarthEvolution of the Earth’’s Atmospheres AtmosphereCarbondioxide

Methane Ammonia Oxygen Nitrogen Others

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

12/27/1412/27/14

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

Evolution of the EarthEvolution of the Earth’’s Atmospheres AtmosphereVolcanic 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.

12/27/1412/27/14Carbon dioxide in the atmosphereCarbon dioxide in the atmosphereThe 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

12/27/14PollutionPollutionWhat 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.

12/27/14PollutionPollutionHumans 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 worse

Causes acid rain

Makes buildings dirty and makes asthma worse

Displaces oxygen in red blood cells that can result in death

12/27/14Section C1.2 – PollutionSection C1.2 – Pollution

12/27/14FuelsFuelsFuels 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.

12/27/14Burning HydrocarbonsBurning Hydrocarbons

Burning hydrocarbons will produce water, carbon dioxide and energy:

CH

H

H

HOO

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.

12/27/14More 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:

12/27/14Other products of burning fuelsOther products of burning fuelsSulphur 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

SOO

Sulphur Oxygen+

Nitrogen monoxide

NO

NO

Oxygen+

OO

Nitrogen

NN

OO

Oxygen+Nitrogen monoxide

NO

NO

Nitrogen dioxide

N OO

N OO

12/27/1412/27/14Conservation of mass in reactionsConservation of mass in reactionsIn 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 ClClH

H 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

CH

H

H

HOO

OO

OH H

OH H

CO

O

Example 2 – Burning methane

12/27/14Incomplete CombustionIncomplete CombustionAs well as producing carbon monoxide, incomplete combustion can also produce soot:

Little oxygen:

CCH

H

H

H

Methane

OO

Oxygen+

OH H

OH H

Water+Carbon

“Soot”

12/27/1412/27/14Burning Fossil FuelsBurning Fossil FuelsBurning fossil fuels like oil and coal causes pollution.

Oil contains carbon:

CH

H

H

HOO

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.

12/27/14Summary of pollutantsSummary of pollutants

C

Carbon

CO

O

Carbon dioxide

Nitrogen monoxide

NO

Nitrogen dioxide

O NO

SO

O

Sulfur dioxide

OH H

Water

C

Carbon monoxide

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:

12/27/14C1.3 Improving Air QualityC1.3 Improving Air Quality

12/27/14Removing 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

12/27/1412/27/14Removing SulfurRemoving Sulfur 12/27/14

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.

12/27/14Wet 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.

12/27/14Reducing Pollution from vehiclesReducing Pollution from vehiclesA number of suggestions:

1) Buy a new, smaller, more efficient car

2) Use legal limits (e.g. An MOT) to enforce lower emissions

3) 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

12/27/14Alternative 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:

12/27/14Making choices about pollutionMaking choices about pollutionChoices 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