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

Questions

1. 1. Which of these compounds in your body does NOT contain carbon?

   • fat
   • carbohydrate
   • protein
   • water
   Check

2. 2. Which process takes carbon dioxide out of the air?

   • decomposition
   • photosynthesis
   • combustion
   • respiration
   Check

3. 3. Which processes put carbon dioxide back into the air?

   • feeding and combustion
   • photosynthesis and respiration
   • photosynthesis and feeding
   • respiration and combustion
   Check

4. 4. How do decomposers return carbon to the air?

   • They photosynthesise.
   • They burn the waste.
   • They respire as they break down dead things and waste, giving out carbon dioxide.
   • They turn waste into coal.
   Check

5. 5. In which kind of place are dead organisms most likely to turn slowly into fossil fuels?

   • on top of the soil in a field
   • in a compost heap
   • on a warm forest floor
   • deep in a bog or the sea bed, where there is no oxygen
   Check

6. 6. How long does it take for dead organisms to turn into fossil fuels like coal and oil?

   • about a hundred years
   • a few weeks
   • millions of years
   • a few thousand years
   Check

7. 7. When coal is burned, where does the carbon in it go?

   • It stays in the ash as coal.
   • It turns into glucose.
   • It turns into oxygen.
   • It joins with oxygen from the air to make carbon dioxide.
   Check

8. 8. Plants respire all the time. When do they give out more carbon dioxide than they take in?

   • on bright summer days
   • at night
   • at midday in sunshine
   • whenever it is warm
   Check

9. 9. Match each arrow in the carbon cycle with the process it shows.

   • carbon dioxide in the air → carbohydrates in green plants
   • carbohydrates in green plants → carbohydrates in animals
   • carbohydrates in animals → carbon dioxide in the air
   • carbohydrates in green plants → carbon compounds in fossil fuels
   • carbohydrates in animals → carbohydrates in decomposers

   • photosynthesis
   • feeding
   • respiration
   • fossil fuels being formed
   • decomposition
   Check

10. 10. Hydrogencarbonate indicator turns yellow. What does this tell you?

    • There is no carbon dioxide.
    • There is a high concentration of carbon dioxide.
    • There is a low concentration of carbon dioxide.
    • There is a lot of oxygen.
    Check

11. 📖 This question is about a text that students read in the app.

    11. Why did Arun put a bung in each boiling tube?

    • to keep the shrimp from jumping out
    • to keep the tube warm
    • so no gases could get in from the air or escape
    • to stop light reaching the plant
    Check

12. 📖 This question is about a text that students read in the app.

    12. Which of these did Arun keep the same in his experiment?

    • whether the tube had a plant in it
    • the volume of indicator in each tube
    • the colour of the indicator at the end
    • what was put into each tube
    Check

13. 📖 This question is about a text that students read in the app.

    13. Arun kept the volume of indicator the same in each tube. Which other variable did he keep the same?

    • the time the tubes were left (two hours)
    • whether the tube had a shrimp in it
    • the colour of the indicator at the end
    • what was put into each tube
    Check

14. 📖 This question is about a text that students read in the app.

    14. Why did the indicator in tube B turn yellow?

    • The light made the indicator yellow.
    • The shrimp respired and gave out carbon dioxide.
    • The shrimp photosynthesised.
    • The shrimp used up the carbon dioxide.
    Check

15. 📖 This question is about a text that students read in the app.

    15. Why did the indicator in tube C turn purple?

    • The plant gave out carbon dioxide.
    • The plant made the water too warm.
    • The plant did not respire at all.
    • In the light the plant photosynthesised faster than it respired, so it used up carbon dioxide.
    Check

16. 📖 This question is about a text that students read in the app.

    16. Why did Arun set up tube D?

    • To give the snail more space.
    • To show the indicator does not change colour without living things.
    • To collect oxygen.
    • To make the experiment take less time.
    Check

17. 📖 This question is about a text that students read in the app.

    17. Why did the indicator in tube A stay red?

    • Neither the shrimp nor the plant did anything.
    • The bung stopped the indicator changing colour.
    • The plant used carbon dioxide in photosynthesis about as fast as the shrimp and the plant gave it out by respiration.
    • The shrimp ate the plant.
    Check

18. 18. A tube holding only a water plant in red indicator is wrapped in black paper for two hours. What colour does the indicator become?

    • red
    • purple
    • blue
    • yellow
    Check

19. 19. Why are green plants important in keeping the carbon dioxide in the air from rising too much?

    • They stop animals from respiring.
    • They turn carbon dioxide into fossil fuels quickly.
    • They give out carbon dioxide only at night.
    • They take carbon dioxide out of the air in photosynthesis, balancing what respiration and burning add.
    Check