Surface Area to Volume Ratio and the Relation to the Rate of Diffusion.

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Surface Area to Volume Ratio and the Relation to the Rate of Diffusion

Aim and Background

This is an experiment to examine how the Surface Area / Volume Ratio affects the rate of diffusion and how this relates to the size and shape of living organisms.

The surface area to volume ratio in living organisms is very important. Nutrients and oxygen need to diffuse through the cell membrane and into the cells. Most cells are no longer than 1mm in diameter because small cells enable nutrients and oxygen to diffuse into the cell quickly and allow waste to diffuse out of the cell quickly. If the cells were any bigger than this then it would take too long for the nutrients and oxygen to diffuse into the cell so the cell would probably not survive.

Single celled organisms can survive as they have a large enough surface area to allow all the oxygen and nutrients they need to diffuse through. Larger multi-celled organisms need organs to respire such as lungs or gills.


The reason I chose to do this particular experiment is because I found it very interesting and also because the aim, method, results- basically the whole experiment would be easily understood by the average person who knew nothing about Surface Area/Volume Ratio. The variable being tested in this experiment is the rate of diffusion in relation to the size of the gelatin cube. Another experiment one could do to determine the surface area to volume ratio is to construct a set of cubes out of construction paper- 1 x 1, 2 x 2, 3 x 3 and 4 x 4 (cm).Then use this formula to determine the surface area- L x W x 6 and compare it with the volumes. The formula to determine volumes of cubes is L x W x H. Although that type of experiment will show no insight into SA/V ratio in relation to the rate of diffusion.


1. Agar-phenolphthalein - sodium hydroxide jelly

2. O.1 M hydrochloric acid

3. Ruler (cm and mm)

4. Razor blade

5. Paper towel

6. Beaker


1. A block...
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