Chemistry of the atmosphere

Question 1

How old is the earth

Answer 1

4.6 billion years

Question 2

Describe the composition of the earth’s atmosphere

Answer 2

78% nitrogen
21% oxygen
0.9% argon
0.1% other gases

Question 3

It was thought that when the earth was young it had an atmosphere more like those on Venus and Mars, high in carbon dioxide with some nitrogen. Explain how the atmosphere on earth may have changed.

Answer 3

Oxygen levels increased due to photosynthesis from algae and then more complex life forms as they developed
Carbon dioxide was reduced as it was used in photosynthesis and dissolved into the oceans

Question 4

Describe what happens to carbon dioxide when it dissolves into the oceans

Answer 4

1. It forms insoluble carbonate compounds such as calcium carbonate which sinks as sediment and eventually forms sedimentary rock.
2. It forms soluble compounds which are taken in by animals to form their shells or skeletons. These then eventually become sediment and turn into rock as well.
3. A lot of carbon dioxide was absorbed by algae and plants for photosynthesis. When they died their remains were buried in mud and compressed over millions of years forming crude oil and natural gas.

Question 5

How is coal formed?

Answer 5

In swamps plants died and were buried and compressed over millions of years they formed coal, which is a type of sedimentary rock.

Question 6

Describe a greenhouse gas

Answer 6

It is a gas which absorbs long wavelength infrared radiation given off by the Earth but does not absorb the sun’s radiation.

Question 7

Explain the difference between the radiation given off by the Sun and the Earth

Answer 7

The radiation from the Sun contains electromagnetic radiation in the ultraviolet, visible and infra red regions. The earth being much cooler than the sun only gives off radiation in the infrared region, which has the longer wavelength.

Question 8

Identify the most common greenhouse gases in the atmosphere

Answer 8

carbon dioxide
methane
water vapour

Question 9

How have the amount of greenhouse gases changed on the last 100 years?

Answer 9

1. The amount of water vapour is much the same

2. The amount of carbon dioxide and methane in the atmosphere has increased significantly.

Question 10

What are the effects of increased amounts of carbon dioxide and methane in the atmosphere.

Answer 10

Greenhouse gases reflect the radiation from the Earth keeping the Earth warm.
Scientists believe that the increase in greenhouse gases are causing the Earth to warm up, this is known as climate change.

Question 11

Identify some of the effects of climate change on the Earth

Answer 11

1. Rising sea levels
2. Changing amounts of rainfall
3. Temperature and Water stress
4. Wildlife changes
5. Food production
   6 Storms

Question 12

Explain how climate change could affect wildlife

Answer 12

Some populations could be reduced if their habitat is destroyed eg polar bears in the polar regions as the ice caps melt
Some species may migrate further north as temperatures rise. Eg. some dragonflies have been found in the UK that are only usually found in warmer climates.
Plants may flower earlier, this can cause loss of crops such as apples if the temperature then drops and frosts kill the flowers.

Question 13

Explain how climate change could affect food production

Answer 13

Changes in climate and rainfall would affect the crops grown in different regions due to drought, flooding, higher temperatures and differences in numbers of pests and pollinators.

Question 14

Explain how climate change could affect sea levels

Answer 14

Rising temperatures would melt polar ice caps and glaciers causing the volume of the water in the oceans to increase.
In addition the higher temperature of the water itself increases volume still further.
Increases in volume would lead to a rise in sea levels which would cause catastrophic flooding in low lying countries like the Netherlands, Vietnam, Bangladesh and the Pacific islands.
Rising sea levels would also increase coastal erosion and tidal surges in port cities such as London and New York.

Question 15

Explain how climate change could affect the number and intensity of storms

Answer 15

It is thought that climate change may increase the frequency and severity of storms. There is however mixed evidence, it appears that there is more rain falling in the severe storms but not that there are more hurricanes.

Question 16

Explain how climate change could affect temperature and water stress

Answer 16

As temperatures rise it is likely that there will be a shortage of fresh water especially around the equator. This does not only affect humans but all creatures in the food chains.

Question 17

What is meant by the term carbon footprint?

Answer 17

The amount of carbon dioxide and other greenhouse gasesgiven out over the full lifecycle of a product, service or event.

Question 18

Describe how a carbon footprint is calculated.

Answer 18

It is the carbon dioxide released from the production, transportation use and disposal of an item
Eg a plastic bag 
Energy to drill for the crude oil
Energy in fractional distillation
Energy in cracking alkanes
Energy to polymerise the ethene
Energy to transport the bag to the shop
Energy to transport the bag to waste disposal
More CO2 released if it is incinerated

Question 19

Identify different methods for reducing your carbon footprint

Answer 19

Increase use of alternative energy
Conserve energy
Carbon capture and storage
Carbon off setting
Carbon taxes and licenses
Carbon neutral fuels

Question 20

Explain how Increasing the use of alternative energy can help reduce your carbon footprint

Answer 20

Using renewable energy sources such as solar, wind and nuclear reduces the need for burning fossil fuels thus reducing the carbon footprint as theirs is considerably lower than the fossil fuels.

Question 21

Explain how energy conservation can help reduce your carbon footprint

Answer 21

Using less energy means that we burn fewer fossil fuels, we can do this by

• using more energy efficient engines in vehicles
• improving insulation in homes so that less heat escapes
• using more energy efficient boilers in heating systems
• using LED bulbs as they require less energy than halogen or filament bulbs
• using better detergents so that we can wash clothes at lower temperatures
• switching off electrical devices instad of leaving them on standby.

Question 22

Explain how carbon capture and storage can help reduce your carbon footprint

Answer 22

A new technology which could reduce carbon emissions by up to 90%. The carbon dioxide produced by burning fossil fuels in a power station can be captured to prevent it being released into the atmosphere. It is then stored deep underground in rocks.

Question 23

Explain how carbon offsetting can help reduce your carbon footprint

Answer 23

This is where something is put in place to compensate for the emmisions from elsewhere. Examples can include

• planting more trees
• setting up renewable energy projects such as wind farms

Question 24

Explain how carbon taxes and licenses can help reduce your carbon footprint

Answer 24

By taxing fossil fuels governments can make fuel expensive, petrol and diesal are expensive in the UK because of tax. Car manufacturers compete to produce more fuel efficient cars to meet the demand for cars which are less expensive to run.
Governments can also issue licenses to limit the amount of greenhouse gases which can be released by businesses.

Question 25

Explain how carbon neutral fuels can help reduce your carbon footprint

Answer 25

Some fuels and processes are carbon neutral, they do not release carbon dioxide into the environment because when they burn the release the same amount of carbon dioxide as they took in during photosynthesis. This is called zero net release.
Ethanol can be made from the fermentation of crops and is carbon neutral.

Question 26

Identify issues and problems with reducing carbon footprint

Answer 26

S- Scientific disagreement
I- International agreement
L- Lack of public information and education
L- Lifestyle changes
E- Economic considerations

Question 27

Explain how scientific disagreement could be a problem in reducing carbon footprint

Answer 27

All scientists do not agree with the causes and consequences of climate change. Some think that extra greenhouse gases are not responsible for climate change, that it is part of the natural warming and cooling cycle of the earth. It makes it more difficult to encourage all countries to reduce emissions as they have arguments for not doing so.

Question 28

Explain how economic considerations could be a problem in reducing carbon footprint

Answer 28

Many of the methods for reducing carbon footprint, such as carbon capture and storage are expensive, making it more difficult for developing countries to take them up.
Many of the underdeveloped countries have stores of fossil fuels which they use to create their electricity, it being much cheaper than nuclear or solar methods.

Question 29

International cooperation

Answer 29

The Kyoto Protocol is a major international treaty signed by many nations to work together to reduce the emission of greenhouse gases.
In the UK they have been reduced by 20% since 1990.
Some countries like the USA refused to sign it- their emissions are the largest in the world!
India and China (together 1/3rd of the worlds population) are exempt
Some countries like Canada signed and then withdrew.
Kyoto expired in 2012 but the Paris agreement was negotiated by many countries in 2015 and will have some impact

Question 30

Explain how lack of public information and education could be a problem in reducing carbon footprint

Answer 30

There is a lack of understanding about the issues of greenhouse gases and climate change in many countries especially in developing countries. The more educated people are about the problems the more effective the solutions.

Question 31

Explain how lifestyle changes could be a problem in reducing carbon footprint

Answer 31

Changes in lifestyle are increasing the demand for energy around the world and as the planet’s population increases this will only get worse.
We use more electrical devices, phones, computers, dishwashers etc
We expect to be warmer in our houses and heat our homes throughout instead of just the living areas.
We travel more, longer commutes to work, more holidays and more long haul destinations as well as more business travel.

Question 32

Explain the term incomplete combustion

Answer 32

Incomplete combustion occurs when a fuel is burnt in a limited supply of oxygen. When burning hydrocarbons this can result in carbon (soot) and/or carbon monoxide being produced instead of carbon dioxide.

Question 33

What is formed when fuels burn?

Answer 33

Burning requires oxygen and the fuels are oxidised during this process
Carbon becomes carbon dioxide
Hydrogen becomes water
Sulphur (present in some fuels) becomes sulphur dioxide

Question 34

Give the equation for burning hydrogen as a fuel

Answer 34

2H2 + O2 —> 2H20

remember to make the numbers for the elements smaller and the first number for the molecule full size!

Question 35

Give the equations for complete and incomplete burning of methane

Answer 35

CH4 + 2O2 —> CO2 + 2H2O complete burning

2CH4 + 3O2 —> 2CO + 4H2O incomplete burning insufficient oxygen

CH4 + O2 —> C + 2H20 incomplete burning even less oxygen

Question 36

Give equations for the complete and incomplete burning of ethanol as a fuel

Answer 36

C2H6O +3O2 —> 2CO2 + 3H2O complete combustion

C2H6O +2O2 —> 2CO + 3H2O incomplete combustion less oxygen

C2H6O +O2 —> 2C + 3H2O incomplete combustion even less oxygen

Question 37

Give equations for the complete and incomplete burning of carbon disulphide

Answer 37

Carbon disulphide CS2 is found in small amounts in oil and burns when the oil burns

CS2 + 3O2 —> CO2 + 2SO2 complete combustion

2CS2 + 5O2 —> 2CO + 4SO2 incomplete combustion less oxygen

CS2 + 2O2 —> C + 2SO2 incomplete combustion even less oxygen

Question 38

Identify some of the common pollutants and products formed when burning fuels

Answer 38

Carbon dioxide CO2
Carbon Monoxide CO
Soot C
Water vapour H2O
Sulfur dioxide SO2
Nitrogen oxides NO and NO2
Unburnt hydrocarbons

Question 39

Explain how carbon dioxide may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 39

CO2 is released when most fuels undergo complete combustion
It is a problem as it is a greenhouse gas and thought to contribute to global warming
The problem could be reduced by using alternative energy sources such as solar and wind as well as improving energy efficiency so less fuel is needed

Question 40

Explain how carbon monoxide may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 40

When fuels containing carbon and burned without sufficient oxygen incomplete combustion produces carbon monoxide
It is a problem because it is very toxic and combines with the haemoglobin in blood reducing its ability to carry oxygen, which can cause death. Also it is colourless and odourless so difficult to detect.
Reduce the problem by ensuring a good supply of oxygen when burning fuels, regular servicing of boilers and other gas appliances.

Question 41

Explain how carbon may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 41

When fuels containing carbon and burned without sufficient oxygen incomplete combustion produces carbon as soot.
It is a problem because it pollutes the air, it can blacken buildings, cause global dimming, reducing the amount of sunlight reaching the earth surface as well as damaging lungs causing breathing diseases.
Reduce the problem by ensuring a good supply of oxygen when burning fuels

Question 42

Explain how water vapour may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 42

Water vapour is produced when many fuels are burned as they contain hydrogen.
It is not a problem despite being a greenhouse gas because human activity does not appear to affect the amount of water vapour in the air as weather patterns control the amount of it in the air.

Question 43

Explain how sulfur dioxide may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 43

Many fuels contain sulfur and sulfur dioxide is produced when it is burned/
It is a problem because sulfur dioxide reacts with water vapour to produce acid rain. The acid rain causes damage to plants, buildings and can also cause respiratory problems for people.
Removing sulphur dioxide from waste gases before they are released into the environment reduces the problem.

Question 44

Explain how nitrogen oxides may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 44

The nitrogen in the air reacts with the oxygen in the air when very high temperatures are reached when fuels are burned.
This is a problem because they can combine with water vapour to cause acid rain which can cause respiratory problems for people.
Removing nitrogen oxides from waste gases before they are released into the environment reduces the problem. This is done in cars using catalytic converters. The way fuel is burnt can be adjusted to reduce the amount produced.

Question 45

Explain how unburnt hydrocarbons may be produced during fuel combustion, whether it is a problem and how that problem may be reduced

Answer 45

If some of the molecules do not burn the unburnt hydrocarbons may be released into the atmosphere.
It is a problem because they are greenhouse gases. It also wastes the fuel.
Ensuring efficient burning so that all of the fuel is used.

Question 46

4.1 kg of a plastic, used to make plastic bottles, has a carbon footprint of 6.0 kg of carbon dioxide.
Calculate the carbon footprint of one plastic bottle of mass 23.5 g

Answer 46

6.0/4.1 × 0.0235
= 0.0344(kg)

Watch out for the units, they need to be the same, if carbon footprint is measured in kg then the mass of the bottle needs to be converted to kg