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B4: Quiz 4 – Answers
B4: Quiz 4 – Answers
1)
a) oxygen or O2
b) High
c) We use the syringe to bring the oxygen bubble to the ruler part where we can measure the length of the oxygen bubble
d) We may miss bubbles and not count them. The gas bubbles will be different sizes. All of these mean that counting the gas bubbles is not an accurate way of finding the amount of gas/ oxygen produced
2)
a) Sodium hydrogencarbonate
b)
i) The student can change the quantity of sodium hydrogencarbonate in the test tubes with the pondweed in
ii) Temperature & light intensity (but we can also have the amount of pondweed, type of pondweed, the time that the pondweed is left for etc.)
c)
c) We use the syringe to bring the oxygen bubble to the ruler part where we can measure the length of the oxygen bubble
d) We may miss bubbles and not count them. The gas bubbles will be different sizes. All of these mean that counting the gas bubbles is not an accurate way of finding the amount of gas/ oxygen produced
2)
a) Sodium hydrogencarbonate
b)
i) The student can change the quantity of sodium hydrogencarbonate in the test tubes with the pondweed in
ii) Temperature & light intensity (but we can also have the amount of pondweed, type of pondweed, the time that the pondweed is left for etc.)
c)
3)
a) Place the test tube with the pondweed into a water bath or beaker of water on top of a Bunsen burner. We then use a thermometer and complete the experiment at a variety of different temperatures
b) Concentration of carbon dioxide & light intensity (but we can also have the amount of pondweed, type of pondweed, the time that the pondweed is left for etc.)
c)
4)
a) The light should not get hot because temperature also affects the rate of photosynthesis; if we had a hot light and moved it closer to the test tube with pondweed, it would cause both light intensity and temperature to increase. If this was the case, we would be unable to say for sure whether the change in the rate of photosynthesis was down to the light intensity changing or the temperature changing
b)
i) Option 4 – light intensity is inversely proportional to the distance squared
ii)
4)
a) The light should not get hot because temperature also affects the rate of photosynthesis; if we had a hot light and moved it closer to the test tube with pondweed, it would cause both light intensity and temperature to increase. If this was the case, we would be unable to say for sure whether the change in the rate of photosynthesis was down to the light intensity changing or the temperature changing
b)
i) Option 4 – light intensity is inversely proportional to the distance squared
ii)
iii) Light intensity decreases by a factor of 4
iv) Light intensity increases by a factor of 9
c)
iv) Light intensity increases by a factor of 9
c)
Questions
1) The diagram below shows the general setup for how we can work out the rate of photosynthesis.
1) The diagram below shows the general setup for how we can work out the rate of photosynthesis.
a) Some bubbles of gas are produced during the experiment. What is the name of this gas produced?
b) During this experiment, we use the quantity of gas produced as a proxy for the rate of photosynthesis. If the rate of photosynthesis is high, will we observe a low or high quantity of this gas being produced?
c) Why do we have a syringe in this experiment?
d) A student suggests that they can investigate the rate of photosynthesis by counting bubbles instead of using the capillary tube, ruler and gas syringe. Explain why counting bubbles is less accurate compared to measuring the length of the gas bubble using a capillary tube, ruler and gas syringe.
2) A student uses the apparatus in question 1 to investigate how the rate of photosynthesis is affected by the concentration of carbon dioxide.
a) What is the name of the substance that when dissolved in water produces carbon dioxide?
b)
i) Explain what variable the student would change in the experiment to measure the effect that the concentration of carbon dioxide has on the rate of photosynthesis. You do not need to talk about leaving the pondweed for a certain period of time and measuring the length of the gas bubble produced etc.
ii) When the student carries out the experiment, what two variables do they need to keep constant?
c) On the empty graph below, draw a curve showing how the rate of photosynthesis changes as the concentration of carbon dioxide increases.
b) During this experiment, we use the quantity of gas produced as a proxy for the rate of photosynthesis. If the rate of photosynthesis is high, will we observe a low or high quantity of this gas being produced?
c) Why do we have a syringe in this experiment?
d) A student suggests that they can investigate the rate of photosynthesis by counting bubbles instead of using the capillary tube, ruler and gas syringe. Explain why counting bubbles is less accurate compared to measuring the length of the gas bubble using a capillary tube, ruler and gas syringe.
2) A student uses the apparatus in question 1 to investigate how the rate of photosynthesis is affected by the concentration of carbon dioxide.
a) What is the name of the substance that when dissolved in water produces carbon dioxide?
b)
i) Explain what variable the student would change in the experiment to measure the effect that the concentration of carbon dioxide has on the rate of photosynthesis. You do not need to talk about leaving the pondweed for a certain period of time and measuring the length of the gas bubble produced etc.
ii) When the student carries out the experiment, what two variables do they need to keep constant?
c) On the empty graph below, draw a curve showing how the rate of photosynthesis changes as the concentration of carbon dioxide increases.
3) A student uses the apparatus in question 1 to investigate how the rate of photosynthesis is affected by the temperature.
a) Explain how the student can modify the experiment to investigate the effect that temperature has on the rate of photosynthesis. You do not need to talk about leaving the pondweed for a certain period of time and measuring the length of the gas bubble produced etc.
b) When the student carries out the experiment, what two variables do they need to keep constant?
c) On the empty graph below, draw a curve showing how the rate of photosynthesis changes as the temperature increases.
4) The diagram below shows how we can measure the effect that light intensity has on the rate of photosynthesis.
a) Explain why we need to use a lamp/ light that does not get hot.
b)
i) Out of the options below, which is correct? Distance for the options below refers to the distance of the lamp from the pondweed.
iii) If we double the distance between the lamp and the pondweed, what happens to the light intensity?
iv) If we third the distance between the lamp and the pondweed, what happens to the light intensity?
c) Complete the graph below to show how the volume of oxygen produced changes as the distance between the lamp and pondweed increases.
b)
i) Out of the options below, which is correct? Distance for the options below refers to the distance of the lamp from the pondweed.
- Light intensity is directly proportional to the distance
- Light intensity is directly proportional to the distance squared
- Light intensity is inversely proportional to the distance
- Light intensity is inversely proportional to the distance squared
iii) If we double the distance between the lamp and the pondweed, what happens to the light intensity?
iv) If we third the distance between the lamp and the pondweed, what happens to the light intensity?
c) Complete the graph below to show how the volume of oxygen produced changes as the distance between the lamp and pondweed increases.