MadSci Network: Chemistry

Re: We did an osmosis expirement in biology, and I have no idea why it worked?

Date: Thu May 15 04:42:32 2003
Posted By: Sean Hunt, Secondary School Teacher, Science, ISM
Area of science: Chemistry
ID: 1042488462.Ch

Dear student,

I will look at your experiment in stages:

  • The first thing you did was to remove the eggshell, this was achieved by dissolving the shell (a base) in vinegar (an acid).

  • Eggs have a layer surrounding them (inside the shell) called a membrane. This layer allows chemicals to pass into and out of the egg. Water is an example.

  • When your egg was placed in water, the water moved into the egg by a process called osmosis. The water 'concentration' inside the egg was less than outside so the water moved in to even things out. This extra water made the egg swell up.

  • When your egg was placed in a sugar solution, the amount of sugar outside the egg was greater than inside. Water had to travel out in order to balance things up. Water leaving the egg would make it shrink.

In more scientific language: The substance, sugar, which has a higher solute concentration than the interior of the eggs, will cause water to leave the eggs’ membrane; the other substance, distilled water, which has a lower solute concentration than the eggs’ interior, will cause liquid to enter the eggs’ membrane.

Hope this helps,

Sean Hunt

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