Chemistry in Pictures: A classic eggsample

Thomas Richmond’s chemistry classes at the University of Utah are rich with labs and demos. When his students understand this classic lab, he says, it “clearly demonstrates that learning is taking place by more than osmosis.” The students first place a normal egg (left) in household vinegar, which dissolves the shell but leaves the internal membrane intact. They then observed the shell-less eggs after they had soaked in pure water (right) and in and a corn syrup solution (middle). All are aqueous systems, but of very different composition. The corn syrup has less water than the egg—it’s hypertonic—so it sucks water out of the egg through the membrane. The water is hypotonic relative to the egg—meaning it has more water, as you might guess—so the egg pulls water inside. The natural movement of water from where it is abundant to where it is relatively scarce is known as osmosis.

Submitted by Thomas Richmond, taken by Ashlee Taft Nelson

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