Gather a handful of tarnished pennies and use different food products to clean them. First, place three pennies in the bottom of a shallow dish and cover them with plain taco sauce. After two minutes, rinse the pennies and compare the side that had taco sauce on it with the side that didn't. You can also try to clean pennies with a combination of tomato paste and vinegar, salt and vinegar, and tomato paste and salt. Discover which of the three main ingredients of taco sauce works the best to clean pennies.
Have your kids try to stick a straw through a potato without bending or breaking it. Then show them how it is done. Hold the potato so that your fingers are on the sides and not the bottom so you do not stab yourself. Hold the straw in the hand that you write with and cover the end with your thumb. Then stab the straw through the narrow end of the potato. The secret is holding your thumb over the end of the straw, which traps the air and gives the straw extra strength.
An egg will sink in a glass of tap water, but if you make the water salty it will float. Dissolve 4 tablespoons of salt into 2 cups of water. Table salt will work fine, but if you want the solution to be clear then use kosher salt. The egg floats in salt water because salt water is more dense than regular water.
Investigate the density of different liquids that can usually be found in your kitchen. Pour 8 ounces of honey into a liquid measuring cup. Then in this order, pour in 8 ounces each of the following liquids: corn syrup, dish soap, water, vegetable oil and rubbing alcohol. Pour each liquid slowly and into the center of the cup. You can also consider tinting the liquids different colors before pouring them in. The liquids do not mix because they have different densities.