Science 9 · Unit 1: Photosynthesis and the carbon cycle · Cambridge Lower Secondary Science Stage 9

Questions

1. 1. Why does more carbon dioxide in the atmosphere make the Earth warmer?

   • It is a hot gas.
   • It lets more sunlight through the atmosphere.
   • It makes holes in the atmosphere.
   • It is a greenhouse gas, so it traps more heat close to the Earth.
   Check

2. 2. Why does sea level rise as the Earth warms?

   • Warm air pushes down on the sea.
   • More rain falls into the sea.
   • Sea water expands when heated, and ice on land melts into the sea.
   • Ice already floating in the sea melts and adds water.
   Check

3. 3. How does cutting down and burning forests affect the carbon dioxide in the air?

   • It has no effect.
   • It decreases it, because fewer trees respire.
   • It decreases it, because the soil absorbs it.
   • It increases it, because fewer trees photosynthesise and burning adds more.
   Check

4. 4. Which of these would help to slow down climate change?

   • cutting down forests for farmland
   • burning more natural gas
   • generating electricity with wind turbines instead of coal
   • driving more petrol cars
   Check

5. 5. An asteroid hit the Earth about 67 million years ago. How did its dust affect living things?

   • The dust fed the plants, so they grew faster.
   • Only animals near the crater were affected.
   • Less sunlight reached the ground, so plants couldn't photosynthesise and animals had less food.
   • The dust made the Earth hotter.
   Check

6. 6. The asteroid collision 67 million years ago caused a 'mass extinction'. What does this mean?

   • one species dying out slowly
   • a very large proportion of species dying out at about the same time
   • a very large animal dying
   • many new species appearing
   Check

7. 7. Match each object with its description.

   • asteroid
   • meteoroid
   • meteor
   • meteorite

   • a piece of rock that reaches the Earth's surface
   • a large rocky object orbiting the Sun
   • a rock burning up in our atmosphere as a 'shooting star'
   • a smaller rock travelling through space
   Check

8. 8. The graph shows the percentage of carbon dioxide in the air, measured since 1960. Which statement does it support?

   • Carbon dioxide in the atmosphere is falling.
   • Carbon dioxide in the atmosphere has stayed the same.
   • There is more carbon dioxide in the atmosphere now than there used to be.
   • Carbon dioxide rose until 1990, then fell.
   Check

9. 9. Use the graph. About what percentage of the air was carbon dioxide in 2020?

   • about 0.041%
   • about 0.035%
   • about 0.031%
   • about 4.1%
   Check

10. 10. Which statement does this graph match?

    • Sea ice in the Arctic is present for fewer months in the year now.
    • Sea level is steadily rising.
    • There is more carbon dioxide in the atmosphere now than there used to be.
    • Sea level rose until 1960 and then fell.
    Check

11. 11. Which statement does this graph match?

    • Sea ice in the Arctic is present for fewer months in the year now, and there is less of it.
    • Sea level is steadily rising.
    • There is more sea ice in the Arctic now than there used to be.
    • There is more carbon dioxide in the atmosphere now than there used to be.
    Check

12. 12. The graph shows how much sea level has risen since 1880. By about how much did it rise between 1880 and 2020?

    • about 2020 mm
    • about 110 mm
    • about 23 mm
    • about 230 mm
    Check

13. 13. Use the graph. How did the rise in sea level change over time?

    • It rose until 1960, then fell.
    • It rose fastest between 1880 and 1900.
    • It stayed the same until 2000.
    • It rose throughout, and faster in recent years.
    Check

14. 14. The graph compares sea ice in the Bering Sea in 2017–2018 with the mean for 1979–2016. What was different?

    • There was less ice, but for more months.
    • There was more ice, for more months.
    • There was no difference.
    • There was less ice, and it was there for fewer months.
    Check

15. 15. Use the graph. What was the most sea ice in 2017–2018, and in which month?

    • about 0.7 million km², in March
    • about 0.8 million km², in July
    • about 0.4 million km², in January
    • about 0.4 million km², in March
    Check

16. 16. To be certain that Arctic sea ice really is shrinking, what extra data would you want?

    • measurements of the sea ice in many more recent years
    • the sea ice in one more month of 2018
    • the air temperature in one city
    • the sea ice on one more day
    Check

17. 17. Why do most scientists think human activities are causing carbon dioxide in the air to rise?

    • Volcanoes are erupting more because of people.
    • People breathe out more carbon dioxide than plants take in.
    • Humans plant too many trees.
    • Burning fossil fuels releases carbon that was locked underground for millions of years.
    Check

18. 18. The carbon dioxide line wiggles up and down every year. The measurements were made in the northern hemisphere. Why does carbon dioxide dip each summer?

    • Plants respire only in summer.
    • Carbon dioxide freezes in winter.
    • In summer plants grow and photosynthesise more, taking in more carbon dioxide.
    • People burn more fuel in summer.
    Check