dropped by 3.2ml. From 80ml-100ml it began to fall at a steady rate again.
Processed Evidence:
Using the line of best fit on the graph, I can conclude that at 45ml oxygen
volume would be about 7.3ml, and at 75ml the oxygen volume would be
2.3ml. This further backs my theory that the rate of oxygen fell at a steady
pace between 10ml and 40ml, but drastically dropped between 50ml and
70ml.
Conclusion:
From the graph I have come to the conclusion that the acid concentration did
affect the rate of oxygen produced. The more volume of acid added to the
flasks, the less oxygen produced. Effectively this is because the acid
concentration slowed down the photosynthesis process in the elodea causing
less oxygen to be produced. This coincides with my original prediction that
the acid concentration would affect the photosynthesis rate resulting in
slower rate of oxygen production. It can be seen on the graph as a steep
drop occurs at 50ml where the rate of oxygen produced slows drastically.
Also on the graph wherever the acid levels were high, the oxygen levels where
low. An example of this is at 10ml, oxygen production was 8.4ml, in
comparison to 90ml where oxygen production had seriously reduced to
1.5ml. From the experiment we now know that acid rain does affect
photosynthesis in water elodea, by slowing down the rate of oxygen
produced.
Acid Rain Experiment:
Evaluation
Accuracy
The experiment was fairly accurate as most of the results were reasonable,
and only one result did not fit the pattern. The errors could have been made
during the recording of the results. Errors could have been made whilst
checking the concentration. More acid could have inadvertently been put
into one flask. Also the timing could have errors. They should have
repeated the experiment to get more accurate results.
Improvements
To improve the experiment they could make sure that all their measurements
are exact and some flasks did not have an acid higher concentration than
others. Also to make the test fairer they could have used the same sized
flasks, got different people to check the measuring and make sure that
everyone got the same times. Also to make the experiment more accurate
they should repeat the experiment at least 3 more times.
Anomalous Results
From the graph it is noticeable that there was one reading which didn’t fit the
pattern. At 20ml the oxygen production was 8.2ml, but this had risen by
0.1ml to 8.3ml at 30ml. This doesn’t fit the pattern as the other results fell
steadily instead of falling, rising, and increasing again. This may have
occurred because slightly less acid was added to the 3rd flask, so the rate of
oxygen produced rose slightly.
Further Work
To provide more evidence they could use another water plant to see if the
acid concentration affected different plants and maybe find out if certain
plants have built up a resistance to the acid. They would have to use the
plants from the same lake as the elodea to make the test fairer.