2Sort Cards J to N (Grey Cards) Into Arguments in Favour of Iron Seeding, and Arguments Against

Phytoplankton are microscopic plants that live in the oceans. Scientists think that these can be used to help to remove carbon dioxide from the atmosphere.

1Sort cards A to I (white cards) to explain how iron seeding can help to remove carbon dioxide from the atmosphere.

2Sort cards J to N (grey cards) into arguments in favour of iron seeding, and arguments against.

AIron is needed for photosynthesis and is often in short supply in the oceans.
BAdding iron can increase the growth of phytoplankton. This also increases the supply of food for zooplankton (tiny animals).
CPhytoplankton use carbon dioxide dissolved in the water.
DAll plants need carbon dioxide to grow, but they also need other nutrients as well.
EIf dissolved carbon dioxide is removed from sea water, more carbon dioxide from the atmosphere will dissolve to take its place.
FThe carbon (as carbon dioxide) is removed from the ocean/atmosphere part of the carbon cycle.
GWhen plankton die, their carbonate skeletons sink to the sea bed and may become buried.
HIf a nutrient is in short supply it may prevent plants growing and reproducing.
IMany plankton make shells out of calcium carbonate or silica.
JExcess fertiliser in rivers and streams encourages algae to grow. When they die, the organisms that make them decompose use up all the oxygen. This kills other life in the stream. This could happen in the oceans. We will only add iron in the middle of oceans, where any plankton that grow cannot affect coastlines.
KThe effects of adding a lot of iron to the sea are unknown. Adding iron could change whole ecosystems. It could kill the fish that many people depend on for food.
LIf adding iron produces results we do not expect, there may be no way to undo the damage.
MThis is a very easy way of removing some of the extra carbon dioxide from the atmosphere, and much cheaper than other methods that have been proposed.
NWe don't know what kind of phytoplankton will grow if we fertilise the oceans in this way. Some species that grow are harmful and could poison coastal plants.

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The flowchart shows one way in which carbon dioxide might be converted into hydrocarbons. (You don't need to remember the details of this method.)

1Some of the processes in the flow chart need energy. Which are these processes?

2If you ignore the steps in the process that require energy, the process as shown in the flowchart produces as much carbon dioxide as it takes out of the air. Explain how it still reduces the amount of carbon dioxide added to the atmosphere overall.

3How will the overall carbon dioxide saving be affected if the energy you identified in question 1:

acomes from a fossil-fuelled power station

bcomes from renewable resources?

4Suggest why step A collects carbon dioxide from power stations rather than from cars and lorries.

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1The gases in the boxes are all found in the atmosphere.Draw a circle round each of the gases that help to keep the Earth warm.

argon / carbon
dioxide / methane / nitrogen / oxygen / water
vapour

2Draw lines to match up the sentences to explain why the temperature of the Earth can vary.

The temperature changes over 24 hours … / … because we have seasons
The temperature changes during the year… / … because of changing amounts of carbon dioxide and other gases in the atmosphere
The temperature may change gradually over many years… / … because we have day and night

3Write down two different human activities that can increase the amount of warming gases in the atmosphere.

______

4The statements below describe two different ways in which chemists can reduce the amount of carbon dioxide in the atmosphere. Tick the boxes to show which method they apply to.

Statements / Iron
seeding / Making hydrocarbon fuels
Carbon dioxide is captured from power station chimneys
Iron is added to the oceans to encourage plants to grow
Carbon dioxide is reacted with hydrogen to make hydrocarbon fuels
These can be used instead of using fossil fuels
Dead sea plants remove carbon from the carbon cycle for a long time

5The graph below showshow levels of carbon dioxide in the atmosphere have changed, and how the world temperature have changed over the last 450 000 years.

What conclusions can you draw from this graph? Tick all the boxes that apply.

Low temperatures occur when there are high levels of carbon dioxide.

High temperatures occur when there are high levels of carbon dioxide.

The high temperatures cause the high levels of carbon dioxide.

The high levels of carbon dioxide cause the high temperatures.

There may be a link between carbon dioxide in the atmosphere and the mean world temperature.

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You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations.

Venus, Earth and Mars are all rocky planets in our Solar System, but their atmospheres are very different. The pie charts show the gases in their atmospheres.

Planet / Mass of atmosphere above 1m2 of the planet (kg) / Calculated surface temperature (°C)
Venus / 1 × 106 / −46
Earth / 1 × 104 / −18
Mars / 2 × 102 / −56

Table 1 – Atmospheric and temperature data

Venus is closer to the Sun than the Earth, and Mars is further away from the Sun. Scientists can work out what the temperature on the surface of each planet should be based on the amount of radiation it receives from the Sun, and how much of this is reflected by clouds in the atmosphere.

These calculated values are shown in Table 1. The calculated value for Venus is lower than that for the Earth because Venus is covered in clouds, which reflect sunlight.

1Explain which of the three planets you would expect to have the lowest surface temperature based on its position in the solar system.

2The mean surface temperature of the Earth is about 30 °C higher than the calculated value.

aExplain why this is so.

bName three gases that contribute to this effect. (Hint: only one of these gases is shown on the pie chart.)

cSuggest why the other two gases are not shown on the pie chart. (Hint: there is a different reason for each of the missing gases).

3The actual surface temperature of Venus is about 500 °C higher than would be expected for the amount of solar radiation it receives. Use the data given above to suggest why this difference is much greater for Venus than it is for the Earth.

4The actual surface temperature of Mars is about the same as would be expected for the amount of solar radiation it receives.

aUsing the data in the pie charts, why might you expect the measured surface temperature of Mars to be higher than the calculated one?

bUse information from the table to suggest why the two temperatures for Mars are actually very similar.

5The average temperature of the Earth’s surface has changed in the past. Suggest whether or not you think the average surface temperature of other planets has changed. Give reasons for your suggestions.

6Many scientists have concluded that human activity may influence the Earth’s temperature. The graph shows one piece of evidence used to back up this idea.

aDoes this graph prove that increased levels of carbon dioxide affect the mean world temperature? Explain your answer.

bDescribe what data scientists use to support the hypothesis that humans are now influencing the Earth's temperature.

cDescribe what scientific idea or model they use to explain the observations of change in temperature.

7Suggest two ways in which human activities could change the amount of carbon dioxide in the atmosphere.

Extra challenge

8aSuggest why there is no pie chart for the Moon.

bHow does the average distance between the Moon and the Sun compare with the average distance between the Earth and the Sun? Explain your answer.

cThe average surface temperature of the Moon is about −18 °C. Why is this much lower than the average temperature of the Earth?

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