Aim: To investigate how carbon dioxide can affect the rate of photosynthesis.
Hypothesis: The rate of photosynthesis in the water plant hydrilla will change as the rate of carbon dioxide changes.
Background information: Photosynthesis
Photosynthesis is the process of autotrophs turning carbon dioxide and water into carbohydrates and oxygen, using light energy from sunlight. Autotrophs are organisms that are able to produce nutrients and organic compounds using inorganic materials. Examples of autotrophs are green plants, algae, bacteria, etc. Organisms which are capable to photosynthesize are called photoautotroph. The chloroplasts (plant cell that contains chlorophyll) in autotrophs trap ...view middle of the document...
Independent variable: 1.The quantity of sodium hydrogen carbonate which produce carbon dioxide in water (2.0g-10.0g). After each time of recording, we increase the amount of sodium hydrogen carbonate by 2 grams to show significant difference between each recording. If we only increase the amount of sodium hydrogen carbonate by 1 gram, the difference between the recordings may not be clearly shown.
2. The water is changed after each recording with the same amount of sodium hydrogen carbonate to prevent leftover sodium hydrogen carbonate (carbon dioxide) in the beaker which would affect the result.
Dependent variable: 1.The rate of bubbles per minute which shows the output of oxygen. Assumed that all the bubbles released from the hydrilla during the experiment are oxygen, we can calculate the rate of photosynthesis because this process releases oxygen and the sugar/glucose produced would remain in the plant.
Control variables: 1.The temperature is controlled at 20°C always. The weather at the time when the experiment is conducted is at about 20°C so the water should cope with the environment. It a bit cold for the plant but slows down the rate of photosynthesis but makes it easier to count the bubbles.
2. Each record time is controlled at 1 minute so that we can calculate the bubbles per minute.
3. The volume of water is controlled at 650ml.
4. The distance between the lamp and the beaker is controlled at 70cm. This cannot be changed because light intensity affects the rate of photosynthesis. If the plant is too close to the lamp, the results would be most affect by light intensity instead of carbon dioxide and the results would not be accurate.
5. The same hydilla plant at all times during the experiment
Uncontrollable Variable: 1.Although a transparent plastic shield is used to prevent extra heat from the lamp affect the temperature of the water, the transparent plastic shield cannot prevent the heat by 100% which the temperature of water might be affected by that.
1 transparent plastic shield
1 glass funnel with plastic tubes to let the funnel sink to the bottom of the beaker which stabilizes the funnel
1 test tube
1 jar of sodium hydrogen carbonate
1 hydrilla (a type of water plant)
Closer look at the beaker:
1. Set up: Measure the amount of sodium hydrogen carbonate (2, 4, 6, 8, 10g) to be mixed with water in the beaker. This is the only independent variable in this experiment.
2. Set up: Measure and pour 650ml of water into a beaker and mix it with sodium hydrogen carbonate using a stirring rod until all the sodium hydrogen carbonate has dissolved into the water.
3. Set up: Place the beaker...