Students can create a salt water tester, which will allow them to determine whether water is fresh or salty----without tasting it----by using electricity. Wrap two popsicle sticks in aluminum foil. Purchase a buzzer from an electronics supply store or through an online merchant. Wrap the red wire of the buzzer around the end of one of the popsicle sticks. Place the other end of the popsicle stick onto the positive end of a 9-volt battery, and tape it into place. Wrap the black wire of the buzzer around one end of one of the popsicle sticks. Place the other end of the popsicle stick onto the negative end of the battery, and tape it into place. When the tips of the popsicle sticks are placed into a glass of water, the buzzer will remain silent, but when they are placed into salt water, the salt will cause the circuit to complete and will make the buzzer sound.
According to PBSKids.org, when an average egg is placed into a glass of water it will sink to the bottom. When an egg is placed into a glass of salt water, the water will be heavier than the egg and will cause the egg to float. To demonstrate this activity, fill two glasses half way up with water, and pour 4 tbsp. of salt into one of the glasses. Place an egg into each glass. The egg in the salty water will float.
You can show students how acidic substances eat materials by demonstrating how acidic lemon juice will clean corroded pennies. Fill a glass half way up with concentrated lemon juice. Place a few corroded pennies into the glass, and allow them to remain there for a few days. When you remove the pennies and buff them with a towel, they will be shiner and clean.