In this experiment, we first see an acid-base reaction. Eggshells contain calcium carbonate which is a base while vinegar contains acetic acid.
When you submerge an egg in vinegar, an acid-base reaction causes the calcium carbonate to break down into their calcium and carbonate parts.
The calcium ions (as in calcium acetate) stay dissolved in the vinegar while the carbonate goes on to make carbon dioxide.
Carbon dioxide is a gas that forms the bubbles you will see around the egg as the eggshell is dissolving.
Inside the egg, there is a semi-permeable membrane that becomes visible after the eggshell has dissolved. This membrane allows the vinegar on the outside to move through, or permeate, to the inside through osmosis.
So vinegar moves from area of high concentration through the membrane to area of low concentration to equalize the densities on both sides of the membrane, causing the egg to enlarge.
- a raw egg
- a deep bowl
- white vinegar
- adult supervision
- Put the raw egg in the deep bowl.
- Fill the bowl with white vinegar until the entire egg is submerged (or floating).
- Leave the bowl at a place where it won't be disturbed for a few days.
- Observe carefully everyday what happens to the egg. You should see the eggshell dissolve over the next few days.
- After the eggshell is gone, leave the egg there for two more days.
- After a week, you should see a soft and semi-transparent egg that is bigger in size than before.
- Take the egg out, rinse it under tap water and play with it.
- Try to bounce it off the ground and see how high you can drop it from without breaking it. (Start low!)
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Now that you have learned about osmosis, can you come up with an experiment that can shrink a raw egg?