- The temperature will affect the rate of photosynthesis because the warmer the water is the quicker the plant will perform photosynthesis. There I will use a thermometer to measure the temperature and the large volume of water to keep it cool. The temperature will help speed up the rate of photosynthesis.
Method: Step 1- I will collect my equipment and pour 1 litre of water into a beaker.
Step 2- Cut a piece of pond weed 5cm long and place it into a funnel. Attach the funnel to the bottom of the beaker using plastercine. Place a test tube over the top of the funnel so that the bubble so that the bubbles can clearly be seen in the test tube. Finally, add Sodium Hydrogen Carbonate to add CO2 to water.
Step 3- Place a lamp 100cm away from the beaker and leave to settle for a minute. Count the number of bubbles for a minute and note down the number.
Step 4- Move the lamp to the next distance away from the beaker. Note down the number of bubble after a minute.
Step 5- Repeat the investigation again with each distance to get two sets of results.
Step 6- Work out the average number of bubbles for each distance of the lamp away from the beaker.
I will use the following distances for the distance between the lamp and the beaker:-
- 10cm
- 20cm
- 30cm
- 40cm
- 50cm
- 60cm
- 70cm
- 80cm
- 90cm
- 100cm.
Safety: - I will watch that I don‘t electrocute myself because I am using water and electricity.
- I will watch that I don’t break any beakers, test tubes or funnels and if I do that I don’t cut myself.
Fair Test: I will only change the distance between the lamp and the beaker during my investigation. I will make sure that I keep the amount of CO2 at a level were it will not be a limiting factor and affect my investigation, the amount of water at 1 litre, the temperature at 27oc, the amount of sunlight, the length of the piece of plant at 5cm and the time I measure the number of bubbles for at 1 minute the same during the investigation to keep it a fair test.
Equipment: - Beaker with 1 litre of water in it
- Funnel
- Test Tube
- Aquatic Plant (Pond Weed)
- Meter Rule
- Lamp
- Sodium Hydrogen Carbonate
- Stopwatch
- Thermometer
Preliminary- My preliminary work was an experiment in which the
Work plant produced bubbles and then I tested the bubbles with a glowing splint to check that the gas was oxygen.
- My preliminary work is connected to my main investigation because I will use the same equipment layout and method except count the number of bubble produced at different light intensities.
- My method for my preliminary work was:
Step 1- I will collect my equipment and pour 1 litre of water into a beaker.
Step 2- Cut a piece of pond weed 5cm long and place it into a funnel. Attach the funnel to the bottom of the beaker using plastercine. Place a test tube over the top of the funnel so that the bubble so that the bubbles can clearly be seen in the test tube. Finally, add Sodium Hydrogen Carbonate to add CO2 to water.
Step 3- Collect the gas produced by the bubbles in the top of the test tube.
Step 4- Take a lighted splint place over the mouth of the test tube. If the gas is oxygen then the flame stays alight.
Conclusion: - My results from my investigation seem fairly accurate because there is the same number of dots on each side of my line of best fit. I used two sets of results to get an average because they will be more accurate. I can conclude from my results that as the lamp is placed closer to the plant therefore the light intensity is higher that there is more photosynthesis been performed and therefore more bubbles.
- This helps prove that my prediction was correct because I predicted that as the light intensity increases the number of bubbles would increase. I was also correct to predict that as the light intensity decreases the number of bubbles decreases.
- This is because light is needed to perform photosynthesis, as it is the main energy source, which is used to build the glucose molecules. However, there is a limiting factor in my investigation, which is the amount of CO2. This will mean that there will be a point when the plant cannot perform photosynthesis any faster however high the light intensity is. Therefore, I will add sodium hydrogen carbonate in an amount that it will mean that CO2, is not a limiting factor in my investigation. The pond weed will be therefore be able to perform photosynthesis at any light intensity, and the trend of my results will not be affected.
Evaluation: - My results are mostly accurate because most of my dots are close to or on my line of best fit, which shows that they follow a certain trend hopefully to reinforce my prediction. I have obtained one anomalous result from my investigation which was when the lamp was at a distance of 10cm from the plant. I could have obtained this anomalous result because there wasn’t a constant stream of bubbles coming from my plant all of the way through the investigation. This could have affected the result because there wasn’t a constant stream so very little bubbles were coming out of the plant at this time. The bubble size wasn’t always constant during my investigation either because at some lengths large bubbles were being produced by the plant and at others only small bubbles were being produced. However, although these two factors could have affected this anomalous result they do not affect the overall validity of my results because I will not include this result from my conclusion and evaluation of the investigation. However, if I had received several anomalous results then they would have affected the overall validity of my results. During my investigation I had only one person counting the number of bubbles so that it was also constant.
- I could have improved my investigation by making sure that there was a constant stream of bubbles being produced by the plant and by making sure that most of the bubbles were roughly the same size. However, this is impossible to do so it will always be a problem in analysing whether my results are accurate or not. To make it easier for the person to count the number of bubbles that were being produced by the plant you could use a long thin tube instead of a test tube. This would allow it to be easier for the bubble to be seen and the gas collected at the top of the tube would be easy to see. I would also be able to measure the volume of gas that was collected at the top of the tube after I have counted the bubbles and see how this changes at different distances of light intensity. I could repeat my investigation more times over to get more readings so that I would get a more accurate average. I would also be able to spot out weak points in the reading because if they are not of a similar amount then something must have been done wrong. I also compared my results with the rest of the class to check that my averages were of similar value to theirs to help prove the validity of my results.
- My prediction is proved by my conclusion because they match. In my prediction I said that as the light intensity increases the rate of photosynthesis would increase as well. Likewise, as the light intensity decreases the rate of photosynthesis decreases. I have proved this prediction because I carried out 10 readings of distance between the plant and lamp each twice, which was good. However, I could have supported my prediction even better with my results if I had performed the 10 readings not twice but three times. If the two results that I did get though were close together then they helped prove the accuracy of my results. I also compared my average results with the rest of the class and my results were close compared with their average results, so this also helped prove the accuracy of my results. During my investigation the temperature didn’t change significantly enough to affect the validity of my results. The temperature increased by just one degree on average, whereas if it had increased by a larger amount like 10oc then the rate of photosynthesis would have doubled and therefore destroying the validity of my results.
Further: - I could further my work by performing the same
Work investigation except at a different temperatures. I performed this investigation at 27oc, I could see how the rate of photosynthesis is affected at different temperatures, without changing the light intensity.
Prediction: - I predict that if I performed this investigation as the temperature increased the rate of photosynthesis would increase. Therefore, as the temperature decreases the rate of photosynthesis would decrease.
Variables: Temperature - Independent
Number of Bubbles Produced - Dependant
Amount of CO2 - Control
Amount of Water - Control
Light Intensity - Control
Amount of Sunlight - Control
Size of Plant - Control
Time Measured For - Control
Method: Step 1- I will collect my equipment and pour 1 litre of water into a beaker.
Step 2- Cut a piece of pond weed 5cm long and place it into a funnel. Attach the funnel to the bottom of the beaker using plastercine. Place a test tube over the top of the funnel so that the bubble so that the bubbles can clearly be seen in the test tube. Finally, add Sodium Hydrogen Carbonate to add CO2 to water.
Step 3- Cool the water to 5oc, and place a lamp 50cm away from the beaker and leave to settle for a minute. Count the number of bubbles for a minute and note down the number.
Step 4- Heat the water to the next temperature which is 10oc. Note down the number of bubble after a minute.
Step 5- Repeat the investigation again with each different temperature to get two sets of results.
Step 6- Work out the average number of bubbles for each temperature of the water in the beaker.
I will use the following distances for the distance between the lamp and the beaker:-
- 5oc
- 10oc
- 15oc
- 20oc
- 25oc
- 30oc
- 35oc
- 40oc
- 45oc
- 50oc
- 55oc
- 60oc