c Both the candles in gas jars Y and Z can burn for some time They go out after

C both the candles in gas jars y and z can burn for

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(c)Both the candles in gas jars Y and Z can burn for some time. They go out after 24 seconds and 16seconds respectively. What conclusion can you draw?(2 marks)(d)After the candles go out, some liquid droplets are seen on the inner surface of the gas jars. What arethese liquid droplets? How can you test for this substance? (3 marks)(e)Describe how the liquid droplets form. (2 marks) ## (a) Carbon dioxide (1m) © Aristo Educational Press Ltd 2013 42 XYZgas Pgas Qgas R
Understanding Integrated Science for the 21st Century (3rd Edition) – Form 2 Unit 7: Living Things and Air (New Questions Update in 2013) (b) We can use hydrogencarbonate indicator. The original colour of hydrogencarbonate indicator is red. When the concentration of carbon dioxide is greater than 0.03%, the colour of the hydrogencarbonate indicator will change from red to yellow. (3m) (c) The amount of oxygen in gas jar Y is more than that in gas jar Z. (2m) (d) It is water. We can use a piece of dry cobalt chloride paper to test for it. It changes from blue to pink in the presence of water. (3m) (e) Water vapour is formed while the candle is burning. Then, water vapour condenses on the cold inner surface of the gas jar. (2m) ## Skill assessed Marks (a)-(e) Understanding concepts 11|!|3eELA0072102027|!|Diana wants to study the process of photosynthesis. She prepares two experimental set-ups as shown below.set-up A set-up B(a)Which set-up is better for measuring the rate of photosynthesis? Explain briefly. (3 marks)(b)Draw and label the control for the set-up you have chosen in (a). (4 marks)plastic bagsunlightsunlightwater plantwater potted planttransparent bell jarboiling tube beaker ## © Aristo Educational Press Ltd 2013 43
Understanding Integrated Science for the 21st Century (3rd Edition) – Form 2 Unit 7: Living Things and Air (New Questions Update in 2013) (a) Set-up A. When photosynthesis occurs in set-up A, oxygen will be produced and the water level in the boiling tube will decrease. The decrease in water level can indicate the rate of photosynthesis. (3m) © Aristo Educational Press Ltd 2013 44
Understanding Integrated Science for the 21st Century (3rd Edition) – Form 2 Unit 7: Living Things and Air (New Questions Update in 2013) (b) (4m) ## Skill assessed Marks (a) Understanding concepts 3 (b) Practical skills 4 |!|3eELA0072202028|!| The diagram below shows the human respiratory system. (a)In which structure (P, Q or R) does gaseous exchange take place? Name this structure. (2 marks)(b)State the function the ribs. (2 marks)

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