Salt

Student Objectives: Students will learn that common salt is part of a group of minerals. They will be able to identify some of the characteristics and uses of common salt as well as some methods of mining it.

Tips for the Teachers: Bring in samples of salt such as iodized, free running and rock salt. Discuss the differences between them and what they can be used for.

Suggested Activities:

1. Do an experiment with ice cubes and salt. Sprinkle salt on some of the ice and watch the two samples melt. The ice and salt sample should melt faster.

2. Make a strong saltwater solution and allow it to evaporate in a shallow dish. Observe the salt residue left behind.

3. Bring in and “taste test” salted and unsalted snacks, such as nuts, chips and crackers. Discuss salt and nutrition, “hidden” sodium in canned/prepared foods and overuse vs. taste.

4. Place fresh apple slices in a saltwater solution for a minute or so and remove. Compare to untreated slices after 20 minutes. The salt treatment will slow the browning process.

Measurements/Evaluation:

1. What are the two best sources of salt?

2. Putting salt on ice makes it do what?

3. Some countries use salt as what?

4. One way of mining salt is to dig it out of the ground. Another way is to make a brine and let it do what?

Answer the following True or False.

1. Salt Helps to make meats last longer.
2. Humans do not need salt.
3. Whole communities have moved to be near salt.

 Salt

The salts are a group of minerals that are alike in many ways. The salt that we use in cooking is common salt. It is a combination of metal element sodium and the gas element chlorine, and is called sodium chloride. Chemical salts are like common salt in some ways, but they are made up of different combinations of things.

People have been using common salt longer than anything else to make foods taste better, and last longer. Salt kills germs, and can be used to help keep meats and other foods safe to eat for a long time. The human body needs salt to stay alive. Long ago, whole communities of people moved from one area to another to be near a source of salt. Even though there is plenty of salt on the earth, some countries still use salt as a kind of money.

The two best sources of salt are seawater and salt deposits. The ocean is 3% salt. When seawater evaporates from a container, sodium chloride is left behind. In places where ancient seas used to be, there are large salt deposits. Some of them can be mined underground like coal. Large blocks of salt are cut and taken out, or broken into chunks and dug out. Another way of getting salt out is by forcing water down into the deposit. The water dissolves the salt, and the salty water is called brine. Then the brine is pumped out and into big flat ponds to dry in the sun. When the water evaporates, the salt can be scooped up from the pond bottom.

Besides its uses in food, salt can help people travel more safely in winter. Salt will make the melting temperature of water go down when it dissolves. When salt is put on ice and snow, they will melt, even when the temperature of the air is below freezing. This is why road crews put salt on icy roads and people sprinkle salt on driveways and sidewalks in winter.