Greenhouse Effect and Climate Change

14 Grade 10 Physics questions on Greenhouse Effect and Climate Change, with worked marking schemes. 14 questions are available on this topic in full.

1. Question 1

   1 mark

   The sun sends out mainly visible light, while the warm surface of the earth sends out mainly infrared radiation. This is because:

   A. the earth's surface is at a far lower temperature than the surface of the sun.

   B. plants at the earth's surface use up all the visible light that reaches the ground.

   C. the atmosphere changes sunlight into infrared radiation as it passes through it.

   D. the earth's surface is solid while the sun is made of gas.

   (1 mark)

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2. Question 2

   3 marks

   Explain how the clearing of a large forest such as the Mau contributes to a rise in the amount of carbon dioxide in the atmosphere.

   (3 marks)

   Marking scheme

   - Growing trees take in carbon dioxide during photosynthesis and lock the carbon up in wood, acting as a carbon sink; removing them stops this absorption (1 mark) - When the felled trees are burnt, or are left to rot, the carbon stored in them is released back into the air as carbon dioxide (1 mark) - The bare soil left behind loses its organic matter through decay and erosion, releasing still more carbon dioxide, and no young trees remain to take the gas up again (1 mark)

3. Question 3

   3 marks

   State three human activities carried out in Kenya that add greenhouse gases to the atmosphere, naming in each case the main gas released.

   (3 marks)

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4. Question 4

   4 marks

   Describe four effects that a warming climate is having, or is expected to have, on life in Kenya.

   (4 marks)

   Marking scheme

   Any four, 1 mark each: - Longer and more frequent droughts in the arid north, leading to death of livestock and food shortage - Unreliable and erratic rainfall, so planting seasons fail and yields of maize and beans fall - Heavier storms and flooding that destroy crops, homes, roads and bridges - Shrinking of the ice fields on Mount Kenya and drying up of the springs and streams they feed - Rising sea level at the coast, with salt water entering wells and low-lying farmland - Malaria-carrying mosquitoes and crop pests spreading into the highlands as these become warmer - Tea and coffee growing zones shifting to higher ground, forcing farmers to change crops

5. Question 5

   1 mark

   A factory near Naivasha wishes to cut down the amount of carbon dioxide it adds to the atmosphere. Which measure would achieve this?

   A. Installing more air conditioners so that the workshop is kept cool.

   B. Building a taller chimney so that the waste gases are released higher above the ground.

   C. Buying its electricity from the geothermal power station instead of running a diesel generator.

   D. Burning its waste paper and packaging in the open yard instead of storing it.

   (1 mark)

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6. Question 6

   1 mark

   Learners are discussing the difference between the thinning of the ozone layer and global warming. Which statement is correct?

   A. The two are the same process; ozone thinning is simply the name used for it over the poles.

   B. Ozone thinning is the main cause of global warming, because the gap lets extra heat from the sun through.

   C. Ozone thinning mainly allows more ultraviolet radiation to reach the ground, while global warming is caused by gases trapping infrared radiation.

   D. Ozone thinning cools the earth and therefore cancels out the effect of global warming.

   (1 mark)

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7. Question 7

   1 mark

   Which one of the following activities adds mainly methane, rather than carbon dioxide, to the atmosphere?

   A. Heating limestone in a cement kiln at Athi River.

   B. Roasting maize over a charcoal jiko.

   C. Growing rice in flooded paddies at Mwea.

   D. Running a lorry on diesel along the Nairobi-Mombasa highway.

   (1 mark)

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8. Question 8

   2 marks

   Distinguish between the natural greenhouse effect and the enhanced greenhouse effect.

   (2 marks)

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9. Question 9

   1 mark

   Which one of the following is the best evidence that Kenya's climate has been warming over the last hundred years?

   A. One year in which the short rains failed in Machakos.

   B. A day in Lodwar on which the temperature reached 40 degrees Celsius.

   C. A heavy hailstorm that destroyed tea bushes in Kericho last season.

   D. Records showing that the ice fields on Mount Kenya have shrunk steadily decade after decade.

   (1 mark)

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10. Question 10

    1 mark

    Which one of the following gases present in the atmosphere does not contribute to the greenhouse effect?

    A. Water vapour

    B. Methane

    C. Carbon dioxide

    D. Nitrogen

    (1 mark)

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11. Question 11

    3 marks

    Explain why the air inside a polythene-covered greenhouse on a flower farm at Naivasha is warmer during the day than the air outside.

    (3 marks)

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12. Question 12

    3 marks

    Suggest three practical measures a secondary school could take to reduce the amount of greenhouse gas it releases.

    (3 marks)

    Marking scheme

    Any three, 1 mark each: - Replace the firewood kitchen with a biogas digester or fuel-efficient stove, so that less wood is burnt - Install solar water heaters or solar panels in place of electric heaters and grid-powered lighting - Fit LED lamps and switch off lights and equipment when rooms are not in use - Plant and care for trees on the school compound so that they absorb carbon dioxide - Use one school bus for trips, or encourage walking and cycling, instead of many private vehicles

13. Question 13

    4 marks

    Explain how gases such as carbon dioxide in the atmosphere keep the surface of the earth warmer than it would otherwise be.

    (4 marks)

    Marking scheme

    - Radiation from the sun is mainly of short wavelength and passes through the atmosphere with little absorption (1 mark) - It is absorbed by the land and the sea, which become warm (1 mark) - The warm surface re-radiates energy, but at much longer (infrared) wavelengths because it is far cooler than the sun (1 mark) - Greenhouse gases absorb this infrared radiation and re-radiate part of it back towards the ground, so less energy escapes into space and the surface settles at a higher temperature (1 mark)

14. Question 14

    1 mark

    Tide records at Mombasa show a slow rise in sea level. Apart from the melting of ice resting on land, which of the following accounts for part of this rise?

    A. Increased evaporation leaves the remaining water denser, so it spreads further inland.

    B. Ice already floating in the ocean melts and adds extra water to the sea.

    C. Warmer air presses down on the ocean and pushes the water towards the shore.

    D. Sea water expands as its temperature rises, so the same mass occupies a greater volume.

    (1 mark)

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