HWrkSht 1_21
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This Homework requires you to complete a graph on the GRAPH PAPER in your jotter. Use only a half page of graph paper for each graph. You should complete the graph on the graph sheet opposite the written answers.
1. The apparatus above was used by a student in an experiment.The Elodea was exposed to different light intensities and the rate of photosynthesis was estimated by counting the number of bubbles of gas produced per minute.
a) Construct a line graph of the results.
b) Describe the effect on the rate of bubbling of increasing the light intensity from 5 to 7 units.
c) Suggest a method of changing the light intensity in this experiment.
d) The number of bubbles per minute at each light intensity was counted four times and an average calculated.
Explain why this was good experimental technique?
2.The apparatus shown below was used to measure the rate of photosynthesis at different light intensities by counting the number of bubbles released per minute by the water plant Elodea.
The light intensity was varied by using a brightness control.
The investigation was carried out at both 10ºC and 15ºC.
a) From the graph of the results, describe the effect of increasing light intensity on the rate of photosynthesis at 10ºC.
b) From the graphs, describe the effect of increasing temperature on the rate of photosynthesis.
c) What is the purpose of the glass plate in the experiment?
d) What is the percentage change in the rate of bubbles released at a light intensity of 4 units, when the temperature is increased from 10ºC to 15ºC?
e) What gas is in the bubbles?
f) What is the limiting factor at light intensities between 0 and 8 units at 15ºC?
3. A gardener grew a crop of peas in a polythene tunnel.
a) State two conditions that could limit the rate of photosynthesis in the pea plants.
b) The graph below shows the mass of sugar in the leaves and the concentration of carbon dioxide just above the pea plants at different times of the day.
(i) For how many hours did the carbon dioxide concentration decrease?
(ii) Explain this decrease in carbon dioxide concentration.
(iii) Explain why the mass of sugar in the leaves is as its maximum at 1600.
(iv) Calculate the percentage increase in sugar in the leaves between 0400 and 1600.
(v) Explain why the mass of sugar decreases between 2000 and 0000.
