Put a penny into a balloon. Inflate the balloon until it fits the grasp of your hand. Tie a knot in the mouth of the balloon. With practice you can get the penny to roll on its edge inside the inflated balloon...and you'll have the world's least expensive gyroscope!
Place a small magnet in the rain gutter of your house. After a rain or garden hose roof washing you might find small micrometeorites stuck to the magnet. Some of the flecks will be fly ash or other airborne pollution. But, some will be the remains of falling stars!
In a zip-lock bag, mix equal amounts of Elmer's Glue and water. In a cup, dissolve a small amount of any hand soap or laundry additive that contains borax, or sodium borate. Mix a few spoonfuls of the borax solution into the bag and knead the mixture. You'll soon have a large polymer mass homemade putty made of long vinyl molecules in the glue, cross linked by the borate molecules. It's polymer magic!
To observe the process of plant transpiration, tape a clear plastic dry cleaning bag over the leafy end of a tree branch. After several hours, you should see liquid water collecting in the bag. Do trees sweat?
Create a static charge on a plastic comb by stroking it though dry hair or with a piece of wool cloth. Bring the charged comb near a thin stream of water flowing in your kitchen sink. The falling water will mysteriously bend towards the comb!
You can see small sparks in the mouth of someone crunching on a wintergreen mint candy. Of course, the room needs to be completely dark. The effect is a chemical phenomenon called triboluminescence molecules in the wintergreen oil being broken and generating an electrical discharge.
Soaking a bone in vinegar for several days causes the calcium in its cell walls to be leached out of the bone, leaving behind flexible cartilage. With luck, you can tie the "rubber" bone in a knot.
Using a pencil, draw a one inch square on the back of your hand. Gently push the pencil point at different points within the square. At some locations, the point will feel cold. At others, it will feel warm. And at yet others, OUCH... it might feel a bit painful. Don't push too hard! The pencil point demonstrates your skin contains several types of nerve receptors.