Activity Book

1. Activity Book ANSWER

2. 8.1 Investigation of carbon dioxide production in a living mouse 1 Why is potassium hydroxide solution used in flask A? To absorbcarbon dioxide from the incoming air. One can deduce推論that any carbon dioxide detected in flask C is due to the mouse.

3. 2 What are the functions of the red hydrogencarbonate indicator in flasks B and C? Flask B: To test whether there is any carbon dioxide in the air entering the bell jar. Flask C: To test whether there is any carbon dioxide in the air leaving the bell jar.

4. 3 What can you tell from the result of flask B? Carbon dioxide is absentin the air entering the bell jar. 4 What can you tell from the result of flask C? Carbon dioxide is released (= given out) by the mouse.

5. 5 How would you set up a control for this practical? 如何裝置對照實驗 Set up a similar apparatus (i.e. that is the same in all ways except one aspect / factor) without putting a mouse in the bell jar.

6. 對照實驗 Control experiment (We must learn how to design it when a real context 實際情況 is given.)

7. 6 What precautions should be taken if the mouse is replaced by a potted plant? Explain. Wrap the pot with a plastic bag. Otherwise, carbon dioxide released by the micro-organismsin the soil will affect the results. Cover the bell jar with a black cloth. Otherwise, the plant will absorb carbon dioxide for photosynthesis and this will affect the results of the respiration experiment.

8. Conclusion What conclusion can you draw from this practical? The living mouse gives out carbon dioxide. {注意 : 只能從所知結果推論} Next

9. 8.2 Investigation of carbon dioxide production in living germinating seeds 1 What is the function of the moist cotton wool? To provide the necessary amount of water for germination (種子發芽)

10. 2 Why should the surface of the seeds be sterilized? To kill the micro-organisms on the surface of the seeds. Otherwise, carbon dioxide released by them during respiration will affect the results.

11. 3 What is the reason for having a tube with boiled seeds? As a control* (or control experiment) to show that only living seeds release carbon dioxide. * 有時從簡只說 control

12. Conclusion What conclusion can you draw from this practical? The living seeds give out carbon dioxide.

13. 8.3 Investigation of heat production in a living mouse 1 What is the function of the cotton wool? To prevent heat loss from the chambers. 或 to trap heat inside the chambers.

14. 2 Why are the two clipsopened at the start of the practical? To equalize the air pressure on both sides of the U-shaped capillary tube. This ensures that both liquid levels are the SAME (= at the same atmospheric pressure) at the start of the practical. Next

15. 3 Explain the results. ●Heat is produced by the mouse and it warms up the air in the thin-walled test tube. ● The air in the test tube expands and results in an increase in air pressure. ●This pushes the air out of the test tube and henceforces the liquid level in arm B downwards. Since there is no temperature change in the control (the side without the mouse), the falling of the liquid level in arm B leads to a rise of the liquid level in arm A. 此消彼長

16. 4 Can the practical be carried out for a long time? Why? No. It is because the mouse will use up all the oxygen inside the chamber and die.

17. 5 Which capillary tube, one with a wide bore (闊口徑) or a narrow bore, is more suitable for this practical? Why? A capillary tube with a narrow bore is more suitable for this practical because small change can be obviously recorded.

18. 6 How will the results differ if the mouse is replaced by a frog of the same size? The change in liquid level is smaller. The frog, being a poikilotherm, has a lower metabolic rate and less heat is released from its body.

19. Conclusion What conclusion can you draw from this practical? Heat is produced by the living mouse.

20. 8.4 Design an investigation of heat production in living germinating seeds Design and perform an experiment 1 What are the controlled variables in this experiment? Amount of seeds in the vacuum flasks. Think.

21. 重要 2 What is the independent variable in this experiment? Whether the seeds are living or boiled. 3 What is the dependent variable in this experiment? Temperature as recorded by the thermometers.

22. 4 What is the control in this experiment? The boiled seeds. 5 How are you going to record and present the results? (Answer varies with individual students.)

23. 6 Warm air is lighter than normal air. Would you put the vacuum flasks in an upright or inverted position to minimize heat loss? What else would you do to prevent heat from coming out of the vacuum flasks? Put the vacuum flasks in an inverted position.Plug the openings of the vacuum flasks with cotton wool.

24. 7 How can you obtain faster results? Use more seeds. Remove the testa of the seeds. (testa = seed coat, 種子皮) Next

25. 8 How can you make sure that the results are reliable 可靠? Run the experiment fora longer period of time. Repeat the experiment for a few more times.

26. 9 What precautions should be taken? Put the bulbs of the thermometers in the seeds, not the air inside the vacuum flasks. Make sure that the seeds completely cover the bulbs of the thermometers.Do not fill up the whole vacuum flasks with seeds or there will not be enough air for the seeds to carry out respiration. Next

27. 8.4 Design an investigation of heat production in living germinating seeds Write an experiment report Objective To find out if heat is produced by living germinating seeds. Next

28. 8.4 Design an investigation of heat production in living germinating seeds Procedure • Set up the two vacuum flasks as shown. Home

29. Procedure 2 Note the temperature of each vacuum flask at the start of the practical. 3 Leave the set-ups undisturbed for a day. 4 Record any increase in temperature in the vacuum flasks.

30. 8.4 Design an investigation of heat production in living germinating seeds Results Temperature in flask A increases. Temperature in flask B remains unchanged.

31. 8.4 Design an investigation of heat production in living germinating seeds Analysis and discussion 1Explain the results. Living germinating seeds carry out respiration and produce heat. This leads to an increase in temperature in the vacuum flask. Boiled seeds cannot carry out respiration to produce heat. Therefore the temperature of the control remains unchanged.

32. 8.4 Design an investigation of heat production in living germinating seeds 2 Predict and explain the results if the following seeds are used: aSoaked germinating seeds without sterilization The temperature increase would be much higher than that caused by “ sterilized and living germinating seeds.”This is because the micro-organisms on the seeds also respire and produce heat.

33. 8.4 Design an investigation of heat production in living germinating seeds bBoiled seeds without sterilization (1) At first, the temperature would remain unchanged. (2) When micro-organisms start to grow on the seeds, they carry out respiration and produce heat. (3)This leads to a rapid increase in temperature at a later time of the practical.

34. 8.4 Design an investigation of heat production in living germinating seeds 3 Why are vacuum flasks preferable to conical flasks in this practical? Vacuum flasks are well insulated to prevent heat loss or gain. Next

35. 4 What are the possible sources of errors in this experiment? Suggest ways for improvement. (Answer varies with individual students.)

36. Conclusion Heat is produced by the living germinating seeds.

37. 8.5 Demonstration of anaerobic respiration in germinating seeds 1 What is the function of the wire gauze? To hold the seeds in position and prevent them from falling down.

38. 2 Why is paraffin oil but not water used? It is because water contains dissolved oxygen and the seeds would then be able to respire aerobically. (實驗要求設置無氧環境)

39. 3 Why is it important to avoid the trapping of air between the seeds and the oil? To ensure that the seeds respire anaerobically.

40. 4 Explain the change in oil level in the tube at the end of the practical. The germinating seeds release gas and it forces the oil level downwards.

41. 5 What can you tell from the colour change in the red hydrogencarbonate indicator when it is in contact with the gas collected? The gas released from the germinating seeds is carbon dioxide.

42. 6 How would you set up a control for this practical? Set up a similar apparatus and replace the soaked germinating seeds with some surface sterilized and boiled seeds.

43. Conclusion What conclusion can you draw from this practical? The germinating seeds respire anaerobically and release carbon dioxide. Next

44. Design and perform an experiment 1 Under what condition will yeastcarry out alcoholic fermentation? Anaerobic condition.

45. 2 How are you going to provide the condition in 1 ? • Boil the glucose solution to drive out any dissolved air (and let it cool down). • Add a layer of paraffin oil on top of the mixture of glucose and yeast.

46. 3 What are the controlled variables in this experiment? Temperature, pH, volume of glucose solution, etc. 4 What is the independent variable in this experiment? Whether the yeast is living or dead.

47. 5 What is the dependent variable in this experiment? The production of ethanol, carbon dioxide or heat.

48. 6 How are you going to measure the dependent variable in 5? • Detect the production of ethanol by fanning/enclosing the mixture and smell the air. • Detect the production of carbon dioxide by bubbling the gas released from the mixture through red hydrogencarbonate indicator or lime water. • 3 Detect the production of heat by observing any increase in temperature of the mixture.

49. 7 What is the control in this experiment? Boiled yeast suspension. Next

50. 8 How are you going to record and present the results? (Answer varies with students.)