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Does the size affect the rate of diffusion.

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Introduction

Research question: Does the size affect the rate of diffusion "You are given a block of agar, a thick jelly, which has had the indicator Phenolphthalein added to it. this indicator turns pink on contact with an alkali, and this property will be used to visualize the rate of diffusion of alkali into the block. Cut a block from you rlarge block of agar. One idea I've had is to use the top of a cover slip box, do you have any better ideas? Make the block into a cube using a scalpel and then measure the dimensions. Make another block and reduce each dimension by half. Repeat and reduce the dimension as evenly as possible, further by half. Place your three blocks into a beaker with enough sodium hydroxide to cover them an leave them for exactly ten minutes stirring carefully. Remove the blocks, dry them quickly and then cut them in half and measure how much of the block is left in an uncolored white condition. ...read more.

Middle

After the five minutes the blocks were taken out, dried, and cut. With a ruler then the area and volume that was left uncolored (unaffected by the NaOH). The total volume that was not affected was subtracted from the total volume to find out the volume that was diffused. The percentage was then found of the agar that was not affected. This was then repeated again to obtain an average. Data collection: 1st set of data Size of agar Volume of agar Area non-diffused Volume non-diffused Volume diffused Percentage diffused 2cm 8 1.4 2.7 5.3 66% 1.5 cm 3.4 .9 .7 2.7 79% 1cm 1 .4 .06 .94 94% 2nd set of collection Size of agar Volume of agar Area non-diffused Volume non-diffused Volume diffused Percentage diffused 2cm 8 1.5 3.4 4.6 49% 1.5cm 3.4 1 1 2.4 62% 1cm 1 .6 .2 .8 80% Average: Size of agar Volume of agar Area non-diffused Volume non diffused Volume diffused Percentage diffused 2cm 8 1.5 3.4 4.6 57.5% 1.5 3.4 1 1 2.4 70.50% 1cm 1 .5 .13 .87 87% Variables that could have had affected the rate of diffusion: 1. ...read more.

Conclusion

Although the volume changed only superficially the surface area changed dramatically. This explains the reason for which the cells are microscopic. They need to be so as to be able to get their nutrients in them fast enough, had they been any bigger the diffusion wouldn't be fast enough thus killing the cell. This experiment was done in a rather efficient way as it was finished in a short amount of time. The only problem is that we used 2 different blocks of agar. Next time it would be much best to use the same block to experiment with. To increase accuracy it would be best not to use a scalpel to cut straight edges. A ready made tool that would do the job automatically and more precisely would be more time efficient and accurate. What would be more interesting would be to use different substances to experiment with other than agar, such as play-do, and jell-o. this way we could see which substance is easier to diffuse things in to, and out of. That way we could see which artificial substances are better diffusing, foods or toys. ...read more.

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