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# An experiment to show the relationship between shape and diffusion rate

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Introduction

An experiment to show the relationship between shape and diffusion rate Aim To see whether there is a relationship between the surface area and the diffusion rate Hypothesis I predict that the smaller blocks of agar will turn clear, or diffuse first, as it has a smaller surface area. This is because there is less surface area and volume for the sulphuric acid to diffuse into. Apparatus * Three sizes of agar, 20x20x20mm, 20x20x10mm, 20x20x5mm * 240ml of sulphuric acid [80ml per beaker] * 3 100ml beakers * Tile used for placing the agar * Tissue to wipe off the sulphuric acid off the agar * 3 scalpels * Ruler, measurable in mm * Stop clock * Calculator Method 1. First, cut three pieces of sulphuric acid in the following sizes 20x20x20mm, 20x20x10mm, 20x20x5mm, as accurately as possible 2. Next, fill the three beakers with 80ml of sulphuric acid each 3. Then, prepare the stop clock, and make sure it is has been reset 4. ...read more.

Middle

Surface area/mm� 2400 1600 1200 Volume/mm� 8000 4000 2000 Surface are to volume ratio O:O.3 O:O.4 O:O.6 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. ...read more.

Conclusion

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. ?? ?? ?? ?? Macha Cauchois ...read more.

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