Salt Lapbook

August 20, 2022

Salt Lapbook

The Cover:
The name on the cover was made by watercolor on a strip of watercolor paper...

and then salt is sprinkled on top.
Where the salt falls it absorbs the color around it, making it dark where the salt is and light all around it.

The letters to spell SALT are then cut from it...

making an interesting textured effect.

Also on the front is a diagram of Sodium atoms and Chlorine atoms,

and when the flap is flipped over, it reveals Sodium chloride atoms, or table salt.

Colored Salt:

A few drops of food coloring added to salt...

makes very pretty salt.

Making Salt Crystals:

We did this as a nature study activity as in The Handbook of Nature Study.

These are the salt crystals that formed in a dish outside in a sunny place. It took about 3 days for the water to fully evaporate.

These are the salt crystals that formed in the dish on our piano. It took about a week for the water to fully evaporate from the dish there.

Freezing Salt-Water:

For this experiment, we took three cups and numbered them. In cup #1 we just added 1/2 cup plain water. In cup #2, we added the same amount of water and 1 tablespoon of salt. In cup #3
we added the same amount of water and 2 tablespoons of water. We put them in the freezer and checked them from time to time.

It took an hour and a half for ice to form in any of the cups. There was no ice in cups 2 and 3.
In cup 1, there was just a small amount of ice around the edges.

After 2 hours, there was still no ice in cups 2 and 3,

but it was getting thicker in cup 1.

After 3 hours, there was still no ice in either cups 2 or 3...

but frozen solid in cup 1.

We had anticipated that when cup 1's water was frozen solid, cup 2's water would be slushy and cup 3 would be liquid, but it didn't turn out quite that way.

There was a difference between the cup 1 and cup 3, however.
If you let the solid ice melt just enough to be able to take a thermometer and stir it around for about 3 minutes in the ice and salt water, you will see that the temperature is below freezing. If you measure the temperature in the cup with just water will register right around freezing.

Why is that?

In a liquid state, the molecules of the water have a significant amount of energy. They are free to move around, so they are constantly traveling around their container. To get into a solid state, the molecules have to slow down and stop moving around as much. The only way this can happen is to take energy away from the molecules. As a substance cools, its molecules lose energy. As they lose energy, they start to slow down until eventually they lose enough energy so the they almost stop moving around altogether. At that point the liquid turns into a solid. Well, when the salt is added to the water, the salt molecules also begin moving around in the water. Since the water molecules are attracted to the salt molecules, a chase ensues. The mutual attraction between the two adds more energy. Thus, in order for to get all of the molecules to slow down and stop moving, more energy must be removed. The only way this can happen is by lowering the temperature further. This is called freezing-point depression. This is why they put salt on icy roads and steps in the winter and why the salt helps make ice cream freeze when you are making it. It lowers the freezing point.

Salt & Ice: