To investigate the affect that changing light intensity has on the rate of photosynthesis in Canadian pond weed.

The equation for this is:

                                     Light energy

Carbon dioxide + water ---------------------->  glucose + oxygen

    Chlorophyll

When this is written in scientific terms it looks like this:

6CO  +  6H 0 -----------> C H  O + 6O

Equipment:

                Thermometer, 450ml of water, sodium hydroxide, a beaker, a meter stick, 1 piece of pond weed, a light and a stop watch.

Plan

First of all we set up the light and the meter stick. Then we got our piece of pond weed, making sure it wasn’t too long, and put it in 450ml of tap water. We then put the thermometer in the beaker of water so we could measure the temperature to make sure it doesn’t vary too much making the results inaccurate. Next we put the beaker on the beginning of the meter stick and turned the lamp on. One of us then timed for two minutes and the other watched for oxygen bubbles. We then took down the results, checked the temperature and moved the beaker back 10cm. We moved the beaker back to 50cm before stopping and repeating the experiment another two times so that we can check our results are accurate and get a mean average.

Fair Test

• I will control the length of time that we watch for oxygen bubbles because we will get more air bubbles if we extend the time and less if we decrease making the results inaccurate.
• I will control the length of pond weed because if you get a longer piece of pond weed it may be able to produce more oxygen or vice versa.
• The temperature of the water has to stay the same because otherwise it may take longer for the pond weed to photosynthesis as it does this quicker when hotter it is.

Safety

When doing this experiment we took the following safety precautions:

• We let the lamp cool down before picking it up and putting it away.
• We didn’t put wires across walk ways in case people tripped over them
• If we spilt water on the floor we mopped it up straight away.

Results

Conclusion

As I increased the light intensity the amount of oxygen bubbles also increased.

Explanation