An experiment to show the relationship between shape and diffusion rate

Results

Conclusion

My prediction as to which block will go clear first was correct, being the smaller block, as its surface area to volume ratio was the greatest out of all three, even though there was not much difference between the three values. This is because the third block has a greater surface area for the sulphuric acid to diffuse into the agar, causing the diffusion rate to be greater. The blocks have become ‘clear’ through diffusion caused by neutralization between the sulphuric acid and the agar, which is an alkaline.

Evaluation

Quite a few things did not go as planned in this evaluation, but I have come up with ideas on how to improve them if we do an experiment like this again. Firstly, the jelly size may not be accurate from cutting it, and when it has been stirred, bits of it may have chipped off causing a change in its surface area. Next time, to avoid this, we could measure the block of agar more accurately when cutting it, and also be more careful when stirring the agar and stir softer so that no bits may get chipped off.

Not only that, but the time we place the three blocks of agar into the sulphuric acid may be different, as well as the time we started the stop clock. Next time, we may possibly find a different method of putting in and taking out the agar so that it remains a fair test, and so that there are less mistakes in the test, which may be reduced by having one person per block of agar and beaker, as well as another person for the stop clock and placing it in and taking it out all at the same time as well as starting and stopping the stop clock.

Another complication may have come from the amount of sulphuric acid in each beaker, which may not have been equal. This problem may be reduced by measuring the sulphuric more carefully, maybe with a measuring cylinder before then placing it into the beaker, instead of measuring it into the beaker straight away.

Our measurements of the depth of the clear layer of the blocks of agar jelly may have been incorrect as well, and to prevent this, we could possibly use a microscope next time and use a graticule to measure the depth that the jelly has diffused to obtain a more accurate result.

The last problem I noticed while doing the experiment was when we were blotting the sulphuric acid off the agar. I found that there may have been some sulphuric acid left on the agar after we have blotted it, which may have caused further diffusion and adjusting our result. This is caused from not blotting off enough sulphuric acid off the agar. Next time, we could carefully blot all the sulphuric acid, and use one piece of tissue for each block of agar so that there is no sulphuric acid on the tissue before blotting each block of agar.