What happens when a raw egg is left in vinegar or water for a week?
vinegar (malt is OK but white makes it easier to see
Fill a jam jar (or more) nearly full with vinegar and another with water.
Carefully place a raw egg (still in its shell) in each jam jar.
It should be easy to tell which is water and which is vinegar by the smell but you can mark them.
Get the Beavers/Cubs take them home and observe for at least a week.
When they bring them back, carefully drain away the water or vinegar and see what state the egg is in.
The egg in water will break like a normal egg and won't have changed.
The shell of the egg in vinegar will have gone soft and, if left long enough, will become like a rubber ball. I suggest you don't bounce it because it will make a mess when it splits. Try and crack the egg over a bucket.