two tips of an egg against each other : it won’t break. The same effect can be obtained by putting
some empty toilet paper rolls upright, and placing a board on top: many people can stand on the
board without crushing the rolls , as the resistance is the total height of all the material, i.e. all of the
rolls (remember that they are made from wood).
As the colour of calcium carbonate is white, why are certain eggs pink, or light brown? The answer can
be provided by another experiment: just put an egg in vinegar: acids from the latter will dissolve the
carbonate… and a red membrane will float at the surface; red plus white makes pink, doesn’t it?
Don’t break the shell, and pour its contents onto a plate. We can observe that the yolk (the colour of
which changes from light yellow to dark yellow, and sometimes even green) makes a rather spherical
volume (remember that a membrane prevents any leaking) with the white around.
Look first at the white. You can see that there are various thicknesses which mean that “something”
makes them. And you can see that it is not white, but yellow, slightly green.
To answer these questions, lets investigate the composition of the egg white.
Did you ever cook dry an egg? Just use a non sticking pan, and put an egg white on it, heating very
slowly. Some white smoke appears over the egg white. Placing a cold plate over the smoke shows
that this smoke is water: condensation of the smoke on the plate reforms liquid water that you can
collect is a vessel.
Eventually, the pan will contain only a thin layer of a yellow material. Starting with a egg white of a
mass of approximately 30 g, you are left with a film of only about 3 g. This film is made of “proteins”.
Not entirely, of course, but mostly. Moreover, notice that this film looks like a sheet of gelatin, which
is as expected since gelatine is also composed of proteins.
What this means: if the remaining film weighs 3 g of the original 30 g egg white, egg white is
composed of 90 percent water and about 10 percent proteins.
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