This simple experiment shows that salt water is more dense than ordinary tap water. Fill a tall drinking glass halfway with tap water. Stir in roughly six tablespoons of salt. Slowly and carefully fill the glass almost the rest of the way with tap water. Gently lower the egg into the glass. The egg should drop through the first half of the liquid until it reaches the salty water. The egg will stop here and float halfway through the glass. This is because the salt water is more dense, enabling the egg to float.
This easy experiment illustrates the chemical reaction between lemon juice and baking soda, which produces carbon dioxide (CO2). Fill a regular soft drink bottle about a quarter of the way with tap water. Add a teaspoon of baking soda. Stir with a straw until the baking soda has dissolved. Add the juice from an entire lemon. Very quickly, stretch the opening of a balloon around the top of the bottle. The balloon should begin to inflate. This is because baking soda is a base and lemon juice is an acid. They create CO2 when combined.
This experiment allows you to measure the effect that freezing has on how quickly a candle burns. Take two identical candles. Put one in the freezer overnight and leave the other in a drawer or on the counter. The next morning, place both candles in holders on a stable surface. Have an adult help you light them and supervise. See how long it takes for the candles to burn. Write down the results. If the frozen candle burns more slowly, why do you think this is?
Some people believe that playing music can help plants grow. Test this theory out for your science project. Ask your parents to help you find three plants of the same variety and of roughly the same age and size. Measure the size of each plant and place them in separate rooms. Play rock and roll music on a CD to the first plant for a few hours each day. Play classical music to the second plant for the same amount of time. Play no music to the third plant. Water the plants daily. After a week, measure how much the plants have grown. Has music affected their growth? Which kind of music had a greater effect?