c1 air quality
TRANSCRIPT
12/27/14
Air QualityAir Quality
W Richards
The Weald School
(OCR 21st Century)
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:
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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 Atmospheres AtmosphereCarbondioxide
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 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
12/27/14FuelsFuelsFuels 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:
12/27/14Removing 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