Did you ever hear that rumor as a kid that if you slept with a book under your pillow you’d learn what was in the book by osmosis? I think I tried it once for about 20 minutes then when I couldn’t fall asleep, I ditched book osmosis.
But did you know an egg has osmosis? We tried out this neat experiment from Janice Van Cleave and learned an egg can swell and shrink depending on what fluid it is in. Check it out!
What you need: You really only need one jar, an egg, vinegar, and karo syrup. (We had a control egg for our experiment but could have done without it)
How you do it:
- Measure and record the circumference of the egg
- Carefully add vinegar to an egg in a jar and let it soak for 24 hours
- After 24 hours the egg shell should be dissolved. A white foam will appear on the vinegar indicating the shell is gone
- Carefully measure the egg circumference and record. Our egg grew to a 6″ circumference!
- Pour out the vinegar and add karo syrup to the jar along with the naked shell-less egg.
- After 48 hours the egg should shrink. The egg on the left in the picture below literally cratered
- Carefully remove the egg again and measure the circumference. Our egg shrunk 2″!
What’s the science?
Why did the egg shell dissolve? The vinegar (an acid) is reacting with the calcium carbonate (a base) in the shell letting off carbon dioxide gas. This reaction ultimately dissolves the eggshell and leaves behind the egg membrane. This membrane allows the moisture in the vinegar to pass through and stay within the egg.
But why did the egg shrink in karo syrup? The syrup molecules are too big to pass inside the membrane but the water inside the egg passes to the low water environment in the syrup. Basically, the egg membrane is selective on which fluids pass in and out of it.
So there you have the incredible osmosis egg! Hope you enjoy this one for a fun kitchen experiment or a cool science fair project. Does this work only on syrup? How do other fluids pass in and out of the membrane? Have fun!
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