Each grain of table salt is a tiny crystal. A simple experiment with salt water teaches students how the crystals can combine to make a structure. Fill a clean glass jar half full of tap water and stir in salt until no more will dissolve and it starts to gather in the bottom of the jar. This is the point when the water is saturated with salt. Tie string to a pencil so that a long end hangs down. Rest the pencil over the opening of the jar with the string inside the water and wait for the salt crystals to adhere to them. Have students check the every day for three weeks to record the progress.
When salt is dissolved in water, it may not seem like much, but an experiment using an egg shows your students that it actually makes a big difference. The salt changes the density of the water by making it heavier. Because of this, when you put an egg in a bowl of salt water, it will float, while an egg in a bowl of tap water sinks. Explain to students that the same principle is the reason that a person floats more easily in salt water than fresh.
Use a simple experiment to show students how salt water conducts electricity. Start by covering two craft sticks in aluminum foil. Buy a buzzer at an electronics store that has positive and negative wires. Attach the buzzer's red wire to the positive post of a 9-volt battery. Now tape one foil-covered stick to the buzzer's black wire, and run another black wire from the second foil-covered stick to the negative battery post. Touch the ends of the sticks together. This should make the buzzer work. Now dip the ends of the sticks into a bowl of salt water, about an inch apart. The salt water will make a connection between the sticks and make the buzzer work.
A solar still works with the power of the sun to turn salty water into drinkable fresh water. Start with a glass bowl filled with two inches of salt water. Put a glass inside the bowl as well. It should be shorter than the bowl, but tall enough to not be under water. Cover the whole thing with plastic wrap and tape it in place to make sure the seal is tight. Place a small stone over the wrap on top of the glass. It shouldn't seal off the glass, but will help direct the distill water into it. Now set your still out in the sun and wait for the sun to evaporate the water, leaving the salt in the bowl. The water will collect on the plastic and drip into the glass.