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An experiment to measure the amount of oxygen bubbles given off in different strengths of sodium hydrogen carbonate

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An experiment to measure the amount of oxygen bubbles given off in different strengths of sodium hydrogen carbonate Equipment list * Lamp * Beaker * Boiling tube * Pond weed * Ruler * scissors * Water * Measuring cylinder * Different strengths of NaHCO3 * Paper clip * Stop clock Plan In the experiment I will get a piece of pond weed and cut it to 5cm I will then make sure that the hole is clear and the leaves from that end have been removed so that oxygen bubbles will be able to escape and not get trapped. Once I have done this I will attach a paper clip to the other end to keep the piece of weed in water or the solution. I will then get a beaker and put 200ml of water and into it. After this I would place the boiling tube with 40ml of water and the pond weed into it and turn on the lamp that will be put 20cm away from the beaker and leave for 3minutes so that the weed can get used to the water. ...read more.


I will be using the same amount of pond weed, as the experiments will run over a number of lessons. I will also want it to be the same temperature so that that will not be able to cause any differences. I will also want the same light intensity that is why I will be using a ruler to measure the 20cm gapping each time. I will also be leaving it for the same amount of time so that it will all be fair. Results A table to show the results from our experiment Experiment one 0sec 30 sec 60 sec 90 sec 120 sec 150 sec water 0 0 0 0 1 1 0.25% 0 0 1 1 2 2 0.5% 0 33 67 101 134 170 0.75% 0 2 3 10 14 17 0.1% 0 13 25 29 33 39 180 sec 210 sec 240 sec 270 sec 300 sec Average water 1 1 3 3 3 1 0.25% 3 3 4 5 5 2 0.5% 203 238 274 307 340 170 0.75% 18 25 27 33 43 17 1.0% 46 ...read more.


Looking at my results they back up my prediction as the graph shows the more concentration I use the more oxygen bubbles given off and I am right saying that when I start the experiment in a new lesson the number of bubbles that are given off is less. Evaluation Looking back my method and my results they are pretty accurate. My results are good and I would be happy to use my results to say that the higher the amount of NaHCO3 I use then the faster the rate of oxygen bubbles that will be given off. I can also come to a clear conclusion that when I have had to start with a new piece of pond weed the number of oxygen bubbles has dropped. In my method I could write about why I think that there will be any anomalous results if any. To see if this works in dark we could cut out the lamp so we could do the experiment in dark but it would have to be the same density of darkness otherwise it wouldn't be a fair test. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This report of an investigation into the effect of changing carbon dioxide concentration on the rate of photosynthesis suffers, to some extent, from many of the common weaknesses that are to be found in a lot of GCSE coursework reports. It is worth highlighting some of these in the hope that students who read this essay might avoid making the same errors.

[1] New science specifications are placing a clear emphasis on research skills and the ability to write scientific prose. In this report, the writer omits the introduction and plunges straight into the practical details. Students must make reference to previous work carried out by other scientists and evaluate its usefulness.

[2] Every investigation must begin with a hypothesis linking IV and DV. To be fair, the writer does give a valid prediction with a clear trend stated.

[3] Methods should be written in numbered stages, avoiding the use of 'I'.

[4] Variables should be discussed at length with a clear indication as to how each one is to be controlled.

[5] Conclusions should analyse data, specifically referring to number values and graph trends.

[6] Evaluations need to seek out anomalous data, find reasons for it, discuss how it impacts on the conclusion, look at data reliability, and propose improvements to the methodology.

In view of these weaknesses, this essay can only just be granted 3 stars and would be struggling to gain a C grade at GCSE.

3 stars

Marked by teacher Ross Robertson 24/06/2013

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