The aim of my experiment is to find out how light intensity affects the rate of photosynthesis in elodea (pondweed).

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SCIENCE COURSEWORK

PHOTOSYNTHESIS

Aim:

The aim of my experiment is to find out how light intensity affects the rate of photosynthesis in elodea (pondweed). To do this I will place the light intensity to various distances and observe the amount of oxygen bubble given off from the reaction

Prediction:

I predict that as the light intensity changes the rate of photosynthesis will increases of decreases dependent on the amount of light intensity. This will be observed by counting the amount of oxygen bubble given off from the reaction. The oxygen bubbles are given off as a waste product of the plant.

Hypothesis:

I hypothesised that if the light intensity increases, the rate of photosynthesis will also increase until a certain level is reached. After, the rate of reaction will than fall down, ultimately increase in light intensity will no longer affect the rate of reaction. This is because other factors effecting rate of reaction will be limited for example: carbon dioxide and temperature.

Preliminary work

To check if the range that I chose for my experiment were correct I carried out a preliminary investigation in which I counted the amount of oxygen bubble given off from the reaction at several distances in a given time. To adjust different light intensity I used a lamp at various distances from the reaction of the pondweed. I used the meter ruler to measure the various distances from the plant.

Table of result (preliminary work)

From my opinion I think this experiment was accurate enough to be the foundation for my main experiment because it gave me a good set of results which were reliable since it met my prediction and hypothesis which was, as the light intensity increases the rate of reaction also increases so the closer the lamp to the reaction the more oxygen bubble were given off. The preliminary experiment also helped me to check if the range of 10, 20,30,40,50 were good enough to give me a good set result which I can draw a graph too. The graph for this result was accurate because it gave me a good best fit curve I think it was simple and efficient way of obtaining an idea of the trends for the graph

Variables

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Apparatus used:

  • Pond weed –  of the experiment
  • Lamp – for the light
  • Thermometer – check the temperature
  • Water -
  • Funnel – to keep the pondweed in the same place
  • Screen – to allow light and prevent heat
  • Trough -
  • Boiling tube
  • Spatula
  • Stop watch
  • Mass balance
  • Sodium hydrogen carbonate
  • Meter ruler

Drawing of how the apparatus was assembled:

Method:

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