Apparatus:
- Test tube
- Clamp
- Lamp
- Thermometer
- Stopwatch
- 30cm Ruler
- Light Shield
Diagram
Method: I decided to do a preliminary experiment before the final investigation to make my results more accurate. I investigated how light intensity affects the rate of reaction.
I adjusted to position of the light box find out what distance away from the test tube produced more bubbles. I used a ruler to measure out distances then recorded how many bubbles were produced in a certain amount of time. I then moved the light box to various distances to find the best position.
During this experiment I used white light for every recorded distance to ensue a fair test. I also checked the temperature of the light box after each distance and allowed it to cool down or heat up accordingly. I have put the results of this experiment in a table and graph.
Hazards: I will have to make sure that the temperature of the water in the boiling tube does not go over 45’c because the enzymes in the chlorophyll will be killed and photosynthesis will stop altogether.
Results
The results of the table will now be shown on a graph for clearer understanding of the pattern.
The graph results tell me that the most productive distance is 2cm away from the boiling tube. I predicted this would be the most productive temperature as it is the closest and provides the most heat. To be safe I will keep the lamp 4cm away to stop the water overheating and killing the enzymes. Using this information I can start the initial investigation and find out which colours affect photosynthesis in a pondweed.
Aim: How colour affects the rate of photosynthesis
Prediction: I predict that the colours yellow, white and green will produce less bubbles because the light will be reflected. The colour red and blue, however, I think will produce more bubbles because the light will be absorbed.
Apparatus:
- Lamp
- Coloured plastic sheets (red, green, blue,white and yellow)
- Boiling tube
- Clamp
- Stopwatch
- Thermometer
Method: To begin the experiment I used a white light to see how many bubbles were produced. I positioned the lamp 4cm away from the test tube and placed a coloured plastic sheet in front of it. I then timed how many bubbles were produced during one minute. After recording my results I changed the coloured sheet. I used 5 different coloured sheets altogether.
Diagram:
Hazards: In this experiment the only thing I will be changing is the colour of the sheet. I will be keeping every other variable (i.e.: temperature of water, distance of lamp) the same to keep the test fair.
Safety: I will be following basic lab rules. (Wearing safety goggles) and keeping the lamp away from water.
Results: I will now show my results for this investigation in a table.
I will now show my results in a graph.
Analysis:
The graph and table show my prediction to be correct. The graph shows the amount of bubbles to be highest when the red and blue coloured sheets were used. The red and blue coloured sheets produced more bubbles proving that colours affect the rate of photosynthesis. The yellow, white and green light slowed down the process of photosynthesis. I think this was because the light was being reflected off the plant unlike the red and blue light, which was absorbed.
Conclusion & Evaluation:
I am pleased with the overall experiment, as my prediction was correct. If I were to repeat this experiment I would make sure I repeated the experiment twice to get an average. I was unable to repeat the experiment as I didn’t have time but I know they would’ve made my overall results clearer. To improve the accuracy of the investigation I could only count the bubbles that were of a certain size or only the ones coming from the very end of the plant. Also to extend the investigation I could change certain factors. For example:
- The type of plant
- The length of the plant
- The temperature of the water
You could also use different chemicals in the water to see if that affected the rate of photosynthesis.
I am pleased with this experiment because I managed to do a preliminary experiment and also I used several colours so I could compare the results.
Overall I think the investigation went well although it could be improved in. I also found it quite difficult to keep the investigation fair.
Katie Jones 11MAC