Aim: To confirm the relationship that diffusion of chemicals depends on the ratio of surface area: volume.
Hypothesis: I believe that the rate of diffusion will decrease with the increase in the volume of the cell.
– Two agar cubes were used for each of the two volumes so that more accurate results could have been obtained.
– All agar cubes were of the same size, this was done by using a ruler when cutting the agar.
– All jelly samples were taken from one whole jelly container so the cells will be similar and the depth would remain the same.
– The temperature will remain the same for all beakers.
– We will be using scalpel to cut the jelly therefore we made sure we handled them with care
– We made sure we used the beakers appropriately, so that they did not brake and cause any damage.
Variables: Independent- size of the agar cube
Dependent – Time taken for diffusion
– Room Temperature
– Concentration of the Acid
– The amount of acid
1) Jelly ( Agar in big Petri dish with phenolphthalein in it)
2) Two small Petri-dishes
4) Plastic ruler 15cm
5) Stop watch
6) Four Beakers
7) 0.1 m of hydrochloric acid
1) Obtain the Agar that is in the Petri dish.
2) Using the plastic ruler and the scalpel cut out two agar cubes of 1cm by 1cm. And two agar cubes of 0.5cm by 0.5cm.
3) Collect four test tubes and place one agar cube into each test tube.
4) Obtain the stopwatch
5) Pour the acid into one test tube and start the stopwatch after five seconds add the acid into the next test tube, again after five second add the acid into the third test tube and lastly again after another five seconds add the acid into the last test tube. Make sure to add on the extra seconds accordingly for each test tube after taking down the results.
6) Keep observing each beaker and stirring them at the same time.
7) When the cubes have turned colourless notes down the time taken.
8) Add the extra seconds on accordingly and arrange a table for the results.
Table Showing the Time Taken For Diffusion In the Different Size Of Agar cubes
Cube Size (cm)
Time Taken (sec)
1cm by 1cm
0.5cm by 0.5cm
Analysis & Conclusion: Looking at our graph we can see that as there were just two set of results obtained there were no anomaly and by looking at the graph we can see that our hypothesis was also proved correct because as the cube size increases the time taken for diffusion also increases. Now our hypothesis was that the rate of diffusion will decrease as the volume increase. So as the size increases the volume also increases and therefore as we can see from the graph diffusion now takes a longer time. Also by looking at the graph we can also say that there is a linear trend and one can say as the size of the cube increases so does the time taken for diffusion to occur.
Evaluation: Even though no anomaly was found in the graph, doesn’t mean that this experiment was one hundred percent perfect there were many errors that took place during this experiment. One error was that when cutting the pair of agar cubes they were not exactly the same shape, this could lead us in an unfair experiment as the rate of diffusion can differ from the sizes of the agar pieces. Another error found was that when cutting the agar pieces the length may have been slightly off, again this small error can change the whole results. The other error found was that when starting the stop watch it was never started at exactly the same time the acid was put into it, this could lead to small errors . Also when adding the acid after every five seconds most of the time the acid was not put in on exactly the right time, but again this is not such a big error that it can change the results. If I were to this experiment again I would use a cutting mechanism that cuts out equal part of the agar, and due to time restraints the results had to be obtained all at once, so by doing this experiment again I will make sure that I did each set of results at a time so that minimal error will be found.