Safety
To conduct my experiment safely I will follow normal laboratory rules, which include:
- The wearing of safety goggles to protect my eyes from chemical splashes.
- Standing up to conduct the experiment, therefore reducing the risk of tripping and spilling chemicals.
- Taking care when handling chemicals.
- Taking care when using glassware to prevent injury.
Fair Test
To make this experiment a fair test I will only vary one thing – the light intensity. I will conduct all the tests at room temperature because temperature has an effect on the rate of photosynthesis. The person who is timing will start and stop the stopwatch, both of us will be counting the number of bubbles so we will be able to get and accurate result. We will also repeat each light intensity three times, this is to increase the accuracy of our results.
Variables
The only thing that I am going to change in this investigation it the distance of the lamp from the beaker.
Range
The range that I am going to use will be zero centimetres up until fifty centimetres. I will move the lamp ten centimetres every time.
Method
- First collect all equipment and set it up.
- We are going to cut the end of the Canadian pond weed and attach a paper clip to the end.
- Then we will put the pond weed in to a beaker and add warm water.
- As soon as we see bubbles in the water we will start the stopwatch and time for one minute.
- When we are timing we will count how many bubbles are produced.
- At the end of one minute we will move the lamp away ten centimetres until I reach 50 centimetres and repeat the process in 2-5, until we have three results for each distance that the lamp has been moved.
Diagram
Pre Test Results
Results
Graph
Trend
The trend is – less light intensity the less bubbles are produced.
Conclusion
There were a few limiting factors for this experiment, the limiting factors were light intensity, percentage of carbon dioxide and the temperature. I know this because I have found information from my exercise book and my GCSE Double Science Biology revision guide. In the leaves there is a palisade layer that is packed with chloroplast which contains a lot of chlorophyll. This is where photosynthesis goes on and if there were no palisade cells photosynthesis would not be able to happen properly.
Diagram of a leaf
As the light moves away there is less palisade calls with chloroplast in to hit and this is why photosynthesis may not happen as fast as palisade cells with the light close to them. I found out that the less light intensity the less bubbles were produced.
My results support the prediction I made because I said that if the light intensity is high photosynthesis is going to happen much faster, but if there is less light intensity photosynthesis will not occur as fast as the Canadian pond weed with a high light intensity.
Evaluation
My experiment went according to plan but there were flaws in it. For example, I could have done more tests to gain a more reliable average.
There were a couple of anonymous results, but when I calculated the averages the anonymous results didn’t make a difference. I also think that there is an element of human error involved because handling the pond weed may have an affect and also the lamp that was used may not have been moved accurately. The anonumus results may have happened because the temperature may have dropped or increased, the amount of carbon dioxide may have dropped or increased, and there was a factor of light intensity this is the light outside may have affected the results.
