## Practical place in room. This may affect the

Practical Report

Hypothesis
As the distance between plants and light increasing, the less amount (volume) of oxygen will produced.

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Independent variable
? The distance between the lamps and the plants
? Use ruler to measure the distance (m) between the light source and plants
? The distance our group choose is 10cm, 20cm and 30cm for each experiment.

Dependent variable
? The amount(volume) of oxygen produced during the process
? Observe the oxygen bubble in the top of the test tube and record the volume(ml) of oxygen.

Controlled factors
? Temperature
? To control the room temperature, make sure the windows, doors and heaters are closed, therefore the temperature in whole room remains the same.
? For example, if an experiment is set up close a window and the window is open. The temperature will be lower than other place in room. This may affect the volume of oxygen produce and affect accuracy of the investigate.

? Mass of plants
? To control the mass of the plant, we use electronic balance to measure the mass of the plant and put exact mass of plants into each beaker.
? For example, if we don’t measure the mass and put different mass of plants in each beaker, the more mass of plants will produce more volume of oxygen and this can affect the result.

? Volume of solution
? We use electronic balance to control the volume of solution, we put the correct scale of sodium bicarbonate solution and distilled water in to each beaker.
? If we don’t have the correct scale of the solution which is 1% of sodium bicarbonate solution to the water, the plants will die.

? Time left to produce oxygen
? Start and end the experiments at the same time. Record the time when the experiment set and end. Subtract them and get the correct time.
? If the experiments don’t start at the same time, the time left to oxygen will be different, it will affect the volume of oxygen produced and make the experiment result inaccurate.

Result Table

Distance from light source(m) Trial 1
Volume of O2(ml) Trial 2
Volume of O2(ml) Average
of O2 (ml) Range/difference between
Trial 1 ; Trial 2 Light intensity 1/d2
0.01 7.2 7.5 7.35 0.3 10000
0.1 5 4.1 4.55 0.9 100
0.2 2.2 3.3 2.75 1.1 25
0.3 1.3 2 1.65 0.7 11.11…
Controlled 0.0 0.0 0.0 0.0 0

Discussion

There are two trends showed in the two graphs, for first one, we can see the point with father distance from the light, the volume of the oxygen is lower, it means that the farther distance between plants and light the more volume of oxygen produced. For the second one, the point with higher light intensity has more volume of oxygen, this means the higher light intensity provide the more volume of the oxygen produced. In the table, we can see the 0cm distance from the light which is the shortest produced most volume of oxygen, and the 30cm one which is the farthest produced the least volume of oxygen. These trends and pattern shown is because the higher the intensity of light, the more solar energy is provided per unit of time, and this will make the chloroplasts of the green plant cells produce more volume of oxygen and convert more light energy into chemical energy. Promote the photosynthesis process also the volume of oxygen produced. So as the light intensity increases, the produce of the volume of oxygen increases.

Random Errors:
The random errors can be avoided or analyzed. We can reduce them in experiments and they will affect the precision of measurement.
Refer to the result on the table, I found some value of trial 1 and trial 2 are quite different, and I considered one possible chance for random error.
? The human eyes error
The fluctuations in eye-level may occurred when reading the scale of the test tube. Also, for an accurate result we need to look at the lowest part of the bubble but not the part that near the scale of the test tube. This may also make the random error.

Systematic error
The systematic errors always occur and can’t be analysis. They will affect the precision of the whole experiment, but will not affect the measurement.
Refer to the result on the table, I found trial 1 and trial 2’s value for the 20cm one is very different, I considered two possible chances for systematic error.
? The quality of the plants
Different quality of plants may affect the volume of oxygen produced. If one Ambulia’s vital force is more than the others in the same experiments or the amount of leaves are different, the plants have more vital force or leaves will produce more volume of oxygen and these will affect the volume of the oxygen produced.

? The position of lights
The position of the lights can create the systematic errors. If the position of the light is closer to one of the beaker that contain Ambulia which in the same experiments, it will affect the result and the plant that the light close to will produce more oxygen.

The incorrect experiments tools or electronic scale and also nonstandard use of the equipment may create the systematic error in every test.

Improvement

Compare result with group members
To improve the experiment, firstly we should compare the result with other people in the group in order to avoid the random errors such the fluctuations of eye-level that will create different date and can improve the accuracy.
Repetition
The more repetitions the experiment, the more preciseness it gets. In this process, we can reduce the chance of systematic errors and the effect from external factor.

Set experiment in an airtight environment
We should put the experiments in a place more airtight that may not have window, this can improve the precision of the experiment by control the external factors such as the light intensity and the constant temperature. This can improve the preciseness.

Experiment equipment
BE more careful with the equipment used, we should make sure that every lamp’s light intensity is the same, the scale of the beaker or test tube is correct, the electronic scale is normal and also the quality of the plants. This can improve the entire precision of the experiments and avoid systematic errors by having the correct scale or the same quality of plants.

Conclusion
The purpose of this experiment is to investigate the effect of light intensity on the volume of oxygen produced during a certain period. The plants that have 10cm’s distance from the light produce more volume of oxygen than the one has 30cm’s distance. From this we can inferred that as the intensity of light increase, the volume of oxygen increased. This is due to that the chloroplasts of the green plant cells change the light energy in to chemical energy and higher light intensity provided, the more volume of oxygen produced.

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