Here's a tricky experiment with gravity! First, balance one or more coins in a stack on your elbow.
Then straighten your arm and try to catch the coins!

Here's an experiment with sound. To make a kazoo, get a small plastic comb and tear off a piece of waxed paper which is just big enough to be folded over the comb.
Fold the waxed paper over the top of the comb, then hold the comb against your mouth with your lips open. Make a loud "HUMMMM" sound, and you should hear the kazoo noise as the waxed paper vibrates. Don't just blow onto the comb, it's important to use your vocal cords and make a humming sound. When you get the hang of it then you can make music on your new instrument by humming different tunes!

Hold a hard-boiled egg carefully on one end and try to balance it. Ask someone if he can make it stand up on its end. Let him try a few times, but he can't do it!
Here's the secret! Hold the egg so that the narrow end is pointing up. Now hit the egg onto the table hard enough to break the shell. Now it is standing on one end!

Hold a small plastic cup, and place two dice between the cup and your thumb.
Lift the cup up into the air and release one of the dice.
Can you catch the die in the cup? Now comes the tricky part! Can you lift the cup up into the air and release the other die and catch it so that both dice are in the cup?

Place a piece of paper on the floor, then try to drop a playing card onto the paper.
It's not easy to do!
Hold the card like this, and ask someone if he can drop the card onto the paper. Don't tell him how to hold the card, just let him assume that he is supposed to hold it this way!
When he can't do it, you will be able to do it because you know the trick! The trick is to hold the card as flat as possible, as in this picture. Give it a try!