The intent for this investigation is to discover the amount of oxygen bubbles that leave the elodea plant in the three minutes that my colleagues and I have come up with to be the standard time for the counting of the bubbles.

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In partial fulfillment for the GCSE Biology Course

Aim: The intent for this investigation is to discover the amount of oxygen bubbles that leave the elodea plant in the three minutes that my colleagues and I have come up with to be the standard time for the counting of the bubbles.  In these three minutes the distance of the lamp to the piece of pondweed will increase starting from a determined distance.

All in all, we are trying to test the prediction that the closer the lamp is to a piece of pondweed, the less amount of oxygen produced by the pondweed. I will further this investigation by listing and explaining the endless factors that may have an effect on this investigation.

The factors:

Picking the right factor is essential not only because it has to be one which results in a higher rate of accuracy but also one that is interesting and one that you are able to have a quarrel about. You also have to have a conventional method to the way you will change your factor so the remaining factors stay the same. I will now list the factors and their pros and cons respectively for this investigation:

1.counting bubbles- this procedure is simple and no complex apparatus is needed. On the contrary, there is a chance for low accuracy, the bubbles vary in size, and there can be an irregular rate of bubbles.

  1. Collecting in a gas syringe- this procedure is good quality because you get a direct reading of the volume. Thus you will need expensive apparatus and it is difficult to obtain suitable sized syringes.

3. Collect bubbles by the displacement of water in measuring cylinder- the apparatus is easy to obtain and there is a direct reading of the volume however,  it is awkward to set up and the repeating of the experiment is time-consuming.

  1. Distance moved by an air bubble in a capillary- the results are obtained quickly and it consists of accurate and simple apparatus. On the other hand, it is difficult to place air bubbles in a sensible place.

With the thorough research that I have completed, I have decided, the factor to change is to count bubbles. Presumably, it might to be the most accurate factor to change however; it is simple and easy to do.

Variables

For the purposes of accurate results, in the duration of my experiment, I will only change one of the following variables and make certain the remaining continue to be the same.

  • The length of the pondweed
  • The type of the pond weed
  • The carbon dioxide concentration
  • The type of water
  • The temperature
  • The light intensity
  • The light wavelengths
  • Time from cutting the pondweed to recording the results

 

As my variable, I have chosen to modify the light intensity. This variable will be the only one being altered and I will make sure that everything will stay identical from the beginning of the experiment to the end. None of the apparatus will be changed and neither will the elodea pondweed.  This will make sure that my results are accurate considering the environment I am provided and the equipment I am supplied with.

 

Preliminary Work:

My partner and I had decided to do a set of preliminary works to allow us to understand the investigation thoroughly and to be aware of what we exactly we have to do.

Starting off, there were many aspects of this experiment that we were not sure of e.g. what the distance of the intervals for the moving of the light away from the pondweed should be. This was determined because of two reasons. For one, the efficiency of the oxygen bubbles being created might be very inadequate and the rate at which the oxygen bubbles are being released decreases dramatically. This is why it was difficult to decide what the distance intervals should be. However, coming to the end of our preliminary work, we received advice from our teacher and from the work itself, we decided to use 3cm intervals for our main experiment. Initially however, in our preliminary work we tried 5cm interval, yet this did not satisfy us.

Another aspect we could not decide on was the time that we should allow to measure the amount of oxygen bubbles. Originally, it was decided to do a 5-minute test for each distance. However, as we tried this time in our preliminary work, we noticed that it is quite time consuming. Also, since we wanted to redo each distance three times to increase the level of accuracy for results, it was best to decrease the testing time in order to receive benefits elsewhere.

Next, we had discovered that the angle at which the lamp was providing light could make a dramatic difference. If we provided light to the pondweed from the top it would increase the heat. This can potentially result in denaturing the enzymes, which could than give you inaccurate results. This makes it significant to have the angle at which the light is provided correct. If the light is provided from the side, the water in between the boiling tube and the large tube itself acts as a heat shield and does not let the heat increase which results in far more accurate results. The heat shield should be used efficiently.

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Also, from doing preliminary work, we created a new, more efficient way to stabilize the angle of the light. Elastic bands are put around the light neck of the light so that it will stay secure. This method will save a lot of superfluous movement.

From doing the preliminary work, I also decided that two people should count the oxygen bubbles released mutually so that the least amount of bubbles is missed. It was tough to decide which bubbles we would count, as there are various types of bubbles from large to small. To make it fair, we ...

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