When plants make Carbohydrates they combine Carbon dioxide and water to make glucose and oxygen. Energy is needed to make them combine. Plants use sunlight, But with just sunlight water and carbon dioxide mixed together will not react. The sunlight must be caught and used in the reaction. Plants use chlorophyll to do this. Chlorophyll also makes plants look green.
During our experiment it is important to keep the amount of carbon dioxide the same so that it remains a fair test. All of the control variables must stay the same also.
Method
First a 10cm piece of elodea was placed into a test tube with water next it was placed into a water bath and A lamp was placed 15cm away from the water bath. 0.5g of sodium hydrogen carbonate (NaHCO3) was then added it was left to equalise for about 2minites then A stopwatch was started and bubbles counted for 1minites. This was repeated 2 more times. Then the elodea was taken out and cut 2cm shorter to 8cm and placed with new water in the test-tube along with another 0.5g of sodium hydrogen carbonate. Once again it was left to equalise then the bubbles were counted and repeated. The experiment was then done for measurements of 6cm, 4cm, and 2cm. The results for each length were then averaged and a graph and results table drawn. By adjusting the length of the plant it alters the amount of chlorophyll.
Apparatus
Testtube beaker
Light elodea
Scissors stopwatch
Thermometer water
Sodium hydrogen carbonate
Varibles
The variables that were kept constant were; light intensity 15cm
carbon dioxide (NaHCo3) 0.5Grams
volume of water 50ml
Type of plant Elodea length of experiment 60seconds
Safety
Be careful of pond water, don’t drink it. Be careful not to break glass.
Results
These results support my prediction showing that the more chlorophyll (the longer the plant) the more bubbles (oxygen) is produced. We can display these results in a graph.
A graph to show the amount of oxygen produced by a plant.
Conclusion
I have found out that the more chlorophyll there is the more oxygen is produced. This statement supports my prediction.
Evaluation
To improve this experiment, I would repeat it so I got a more accurate average. I also would have collected the oxygen and measured the volume as bubbles are irregular sizes so it is not accurate. The water in the test-tube could have been measured more accurately using a burette.
