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Investigation of the factors affecting photosynthesis
Introduction
Light is one of the factors which affects the rate of photosynthesis. In this investigation a green plant named Canadian pondweed (Elodea) will produce bubbles of oxygen as a result of photosynthesis. The number of bubbles of oxygen produced is affected by light intensity.
Apparatus
250 cm^3 beaker lamp glass funnel plasticine test tube 8 cm length of pondweed ( Elodea) metre ruler ± 1 mm sodium hydrogen carbonate powder clamp stand, clamp and boss spatula
Diagram of Apparatus
Method
- Place the Elodea in a beaker containing 200 cm^3 of water.
- Add one spatula of sodium hydrogen carbonate to the water.
- Stick 3 small pieces of plasticine to the rim of the funnel and place it upside down over the plant.
- Completely fill a test tube with water and carefully place over the end of the funnel with the end under the water, clamp into place.
- Place the lamp 5 cm away from the apparatus.
- Start the stopwatch and record the number of bubbles of oxygen produced in one minute.
- Repeat the experiment with the lamp 10 cm, 15 cm, 20 cm, 25 cm and 30 cm from the apparatus.
Analysis
- Plot a graph of the distance against number of bubbles produced in 1 minute.
- What conclusions can be reached from your results?
- Evaluate your method and state how it could be improved.
Risk Assessment
Hazard Risk Control measure
Lamps will become hot Burning hand when moving lamp Do not touch lamp until it has cooled down.
Practical techniques covered
B1 Use of appropriate apparatus to make and record a range of measurements accurately, including length, area, mass, time, temperature, volume of liquids and gases, and pH.
B2 Safe use of appropriate heating devices and techniques including use of a Bunsen burner and a water bath or electric heater.
B3 Use of appropriate apparatus and techniques for the observation and measurement of biological changes and or processes.
B4 Safe and ethical use of living organisms (plants or animals) to measure physiological functions and responses to the environment.
B5 Measurement of rates of reaction by a variety of methods including production of gas, uptake of water and colour change of indicator.
