Here are two very simple science experiments you can do with salt to show the effect it can have on water and ice. The experiments both use items that are easy to find and can be done at school or at home with kids ages eight to twelve.
The things you will need for these experiments are:
- 2 styrofoam or plastic cups
- measuring cups/spoons
- ice cubes
- small plastic bowls
- bowl that holds at least 2 cups of water
- eggs (raw or cooked)
- paper towels for cleaning up afterwards.
First of all, you will show how salt lowers the freezing temperature of water to melt ice. This offers an explanation as to why salt is used in winter for icy surfaces.
Next, you will see how much salt concentration it takes to float objects in water and why. When you go swimming in salt water, it is much easier to float because of the salt content of the water.
Experiment #1 – Using Salt to Lower the Freezing Point of Water
- Measure one cup of cold water and split it into the two cups.
- Measure one Tablespoon of salt into one of the cups and mix it well with a spoon. Leave the other cup alone. Place both of the cups into the freezer for ten minutes. You can set a timer if you wish.
- Take the small plastic bowl and at least two ice cubes. Sprinkle some salt on the ice cubes and then watch it melt. The reason this happens is because salt actually lowers the freezing point of water. It will still freeze, but it has to be much colder than the freezing point of fresh, unsalted water.
- When ten minutes is up, take the two cups out of the freezer. Check out that the fresh, unsalted water has begun to freeze. The salted water, however, has not shown any indications of frezing. This is because the salt in the water has lowered the freezing point of the water.
Experiment #2 – Using Salt to Make Objects Float in Water
- Take a bowl that holds at least 2 cups of water and a teaspoon. Fill the bowl with two cups of water.
- Take different objects like a rock, a marble, an apple, and an egg.
- Add some salt to the bowl, one teaspoon at a time, until you find out how much salt is necessary to cause the object to begin to float. Start with the egg – it takes about 9 teaspoons of salt to make an egg float.
- Next, they should try the apple- it will take about 12 teaspoons of salt to make the apple float. Add more teaspoons of salt to make the heavy items float. You will need to add 10 teaspoons of salt to make the marbles float and 14 teaspoons of salt to cause the rocks to float.
Salt/water concentration is a really cool concept to teach children. These two experiments can teach children how salt can affect water in making it freeze quicker to making objects float better. Whether at home or at school, children are sure to have a blast working with salt and water together!