- Fill a glass with water and put one egg into it.
- Fill the second glass with vinegar and put another egg in.
- Wait three or four days.
- The egg in vinegar hasn't got a shell. It's bigger and darker than the egg in water.
Vinegar is an acid and dissolves the calcium in the eggshell. It is calcium that makes the shell hard. A thin flexible membrane just under the shell still holds the egg's shape.
Water does nothing to the eggshell.