HWrkSht 1_19
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1. An experiment was set up to measure the effect of light intensity on the rate of photosynthesis in the water plant, Elodea. The light intensity was varied using a dimmer switch on the bulb.
The rate of photosynthesis was measured by counting the number of bubbles released per minute.
a) Name the gas collected.
The results of the experiment are shown in the table below.
b) Plot a line graph to show rate of photosynthesis against light intensity.
c) Using the data in the table, explain the results obtained at light intensities greater than 8 units.
d) There are two reactions in photosynthesis. The first reaction is photolysis.
(i) Name the two substances produced by photolysis that are required for the second reaction.
(ii) Name the second reaction.
e) Write the word equation for photosynthesis and underline the raw materials.
f) What do green parts store glucose as?
g) Glucose is converted into what structural carbohydrate?
2. The diagram shows a second investigation into the effect of carbon dioxide on photosynthesis.
Destarched leaves were placed in flasks containing liquids as shown.
After 24 hours in well lit conditions, the leaves were tested for starch.
a) State in which flask(s) starch was present.
b) Name two factors which must be kept the same for A and B.
c) How should the apparatus shown in the diagram be improved to make sure the experiment is valid?
A further experiment on photosynthesis was carried out.
After some time, the leaf disc floated to the surface. The disc floats up because bubbles of a gas are produced in the leaf.
The time taken for this was measured.
The experiment was repeated five times.
d) Calculate the average time for the leaf disc to float.
e) Why was it good experimental technique to repeat the experiment 5 times?
f) Name the gas that caused the leaves to float.
g) Name the green chemical, found in leaves which converts light energy to chemical energy
