nearer to the plant more of the plants surface area is coming in to contact with the light from the
desklamp therefore more photosynthesis will occur which will mean more oxygen and glucose
will be produced. Apparatus · Funnel. · Measuring cylinder. · Stop watch. · Card board and
foil(used to fillter the light). · Beaker. · Desklamp. · one metre ruler stick. · Balance. ·
Pondweed. · Carbon dioxide Powder. · Water. · Scapular. Fair Test To ensure that a fair test
is carried out the following things must be done · The same pondweed must be used every time
we change the light distance. · Do th e experiment three times for each distance to get an
accurate average. · There must only be one variable and that is the distance of the light source
from the plant. · Chose a value for carbon dioxide mixture and keep at the same value allthe
way through the experiment(3 grams). · Keep the experiment at a constant 20degres (this is
because more oxygen is produced at this temperature). · Take results after three minutes for
each induvidual experiment. Safety · Follow lab safety rules (eg no running bags at back etc). ·
keep the desklamp away from contact with water. · Be careful when using scapuar. Method ·
Collect apparatus. · Set up apParatus as in diagram. · Fill measuring cylinder and beaker with
water. · Add carbon dioxide mixture to water. · Set up desklamp in correct position(eg 10cm). ·
Turn on desklamp and start stopwatch. · Count the bubbles for the next three minutes and also
make a note of the change in volume. · Record your results. · Repeat experiment twice more for
distance 10cm and then do the same with distance 20,30,40,50,60,70,80,90, and 100cm.
Results These are my results Because my results did not go entirely to plan(because my
pondweed was not photosynthesising quick enough) I have been given a past years results
which I will now usS as my results instead.They are as follows- Analysis Looking at my
results a can see a significant increase in the rate of photosynthesis as the distanse decreases.All
of the results I was given show this pattern.In the experiment when the distance was 50cm there
was not much photosythesis taken place only about 13 bubbles of oxygen were produced,but
when the desklamp was 0cm away alot of photosythesis was occuring on average 184 bubles in
three minutes a quite substanchal difference from 50cm,overall it was a quite significant
increase.I belive This is because when the desklamp is close tho the pondweed more of the
pondweeds surface area has light energy shining upon it which means more photosythesis will
occur in a shorter time. The average no. of bubbles for different distances arebasnfollows-
Looking at my results it is quite evident that the number of bubbles produced is much greater
when the distanse of the pondweed from the desklamp is less.This proves that my original
hypothesis was correct that "as the distance decreases of the desklamp from the pondweed
therefore more oxygen bubbles are produced".As i mentioned before this is because there is
more light energy shining on a greater surface area when the desklamp is closer so therefore
greater surface area equals more photosynthesis. Evaluation I think that on the whole my
experiment was ok.The results i gathered were very odd i belive this is because of the poor
quality of the pondwed we used.But with the set of resuts we were given we were able to
calculate acurate averages which followed my prediction. I belive our measurments were about
as accurate as we could get usill oung the apparatus that we did. We experienced quite a few
problems throughout our experiment.These were first of all in our first experiment our
pondweed was not of a high standard and was photosynthesizing very slowly the only way we
could have got around this problem without using new pondweed would be to leave the
experiment for longer.Another problem we encountered was the change in temperature when
the desklamp was close to the pondweed because we could not do anything to ammend this we
had to accept any slight change in our results.another problem we faced was counting the
bubbles when the plant was photosythesising the bubbles were different sizes,but as talked
about in my pelimenary data we overcame this problem by counting every individual bubble as
one.
