Table Magic
You might want to pass the time by making something disappear.
Take a glass with a thin bottom and set it on top of something flat and easily seen through the water, such as a piece of coloured paper or a coin (a penny works well because of it's dark colour).
Now put a piece of paper or a plate on the rim so that you can't look straight down through the water. When your child looks through the side to see the object underneath, it will have disappeared! But when you lift off the cover and look down, it's still there!
Light bends as it passes through water, so the image of the penny can't be seen from the side.
PENNY CLEANER
Before you make the penny disappear, you might want to clean it first.
All you have to do is lay the penny on a plate and cover it thoroughly with a sprinkling of salt. Add a few drops of vinegar to the salt pile, wait a bit, and you will have one very clean penny!