# Relation Between Shape and Diffusion Rate

**Topics:**Surface-area-to-volume ratio, Cell biology, Chemical kinetics

**Pages:**2 (701 words)

**Published:**April 14, 2013

Aim- To investigate the relationship between the shape of an object and the time taken for a substance to diffuse to its centre. Hypotheses-

Part A) The 5x5x2.5mm block will turn clear first as the Surface area to volume ratio is high and the 10x10x10mm block will take the longest to completely diffuse the Acid to its centre. Part B) The flat, rectangular block will be the first to completely turn clear due to its high Surface Area/Volume Ratio. When measured, the cubic, rectangular block will have a significantly higher percentage of diffusion than the sphere. Materials- ~See attached Sheet~

Method - ~See attached Sheet~

Discussion-

1. It is shown that diffusion took a lot less time when the Jelly block was smaller and had a high Surface Area/Volume ratio. The acid diffused through the 5x5x2.5mm block in about 3 minutes and 5 seconds, but the 10x10x5mm block took around 11 minutes and 25 seconds to fully diffuse, The smaller block has the high Surface Area/Volume ratio, which is why it was the fastest to fully diffuse out of the five Jelly blocks. 2. The acid diffused in the smallest block much more rapidly,The larger block took 16 minutes and 80 more seconds to diffuse completely than the smallest block did. 3. A) The Flat Rectangular block turned clear first, when the flat rectangular block was clear, the Cubic Rectangular block was around 72% Diffused, the Sphere was only 36% discoloured. B) The differences in the degree of discolouration is due to the Higher Surface Area/Volume ratio of the flat rectangular block compared to the lower Surface Area/Volume ratio of the Sphere and the Cubic Rectangular block. C) The acid diffuses into the shapes at different rates, depending on the size and shape of the block. 4. Single Cell organisms are usually microscopic because it is much more efficient for the cell to have a high surface area/ volume ratio (smaller cell). Bigger cells would have a much harder time...

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