Make an inclined plane from a smooth piece of wood with one end propped up on books. Fill a bowl with sand to make it heavy. Experiment with different ways to reduce friction to make the bowl slide down the ramp easier (pour sand or oil on the board, or freeze a thin layer of ice on it).
Show that it takes less effort to lift a group of bricks by using a first class lever than if lifting by hand. Use a board like a "see-saw" with bricks on one end, and you push down on the other end. Place the fulcrum close to, but not under, the end with the bricks.
Prove that the same amount of water takes up more space when it is frozen than when it is in a liquid state. Pour water into two equal-sized aluminum cans that have had their tops removed. Place one in a freezer for several hours. The water will turn to ice and push up, extending out of the can as it expands.
Show the concept of space and mass by weighing five empty aluminum soda cans and measuring the three-dimensional space they take up. Crush the cans and then measure the space they take up. Weigh them to prove that their mass (weight) is still the same.
Hypothesize that the pH (a measure of alkalinity and acidity) changes as a liquid becomes more concentrated. Pour three spoonfuls of lemon juice into a drinking glass filled with water. Stir. Using litmus paper, measure the pH. Place the glass in a warm, sunny window and let most of the liquid evaporate. Check the pH of your concentrated solution.
Take an old, tarnished penny and cover it with tomato sauce. After an hour, rinse it off with warm, soapy water. You have discovered a natural copper cleaner.
Oxidation is the chemical process that occurs when oxygen combines with certain materials. Place a thumbtack, paper clip, iron nail and several other metal objects in a jar of water for several days, then place the objects on a paper towel and let dry. Observe any changes in each object.
Prove that carbon dioxide is heavier than air. Place a votive candle in a drinking glass and light it. Scoop two tablespoons of baking soda into an empty coffee can. Add three tablespoons of vinegar. A violent reaction will result, as invisible carbon dioxide gas is released. After a few seconds, pour the gas from the coffee can into the votive glass, and the candle will be extinguished.