Wednesday, October 29, 2014

Project: THE SALTY SEA, Making Salt Crystals

Salt Crystals
Ocean and sea water is salty.  Some lakes are also made of salt water, but most have fresh water.  Great Salt Lake in Utah, the Salton Sea in California, and Lake Nakuru in Kenya are all salt lakes.
You may have swum in the ocean or a salt-water lake.  Even though the water was clear, you would have been able to taste the salt on your tongue.  When salt dissolves in water, it disappears.  Here is an experiment you can do to make it reappear.

Making Salt Crystals
You will need:
  • 1 cup sea water (If you do not live near the ocean or a salt lake, you can make your own sea water by mixing 2 teaspoons table salt with 2 cups [.5 liter] water.)
  • pie pan
  • magnifying glass

1. Pour the sea water into the pan.  Put the pan in a warm, dry place and let the water evaporate.  This will take a few days.  What do you see when the water is gone?
2. Look at the salt crystals with the magnifying glass.  What shape are they?  Each kind of mineral forms its own crystal shapes.  Can you see the X-shaped indentation on the top of each crystal.

About two-thirds of the salt that is dissolved in sea water is sodium chloride, or ordinary table salt. When water evaporates from the sea, the salt is left behind, just as it was in your salt crystal project.  This means that the water vapor in the atmosphere, which falls back to Earth as rain, is fresh water.

You can find this project and many others in my book The Geography Book: Activities for Exploring, Mapping, and Enjoying Your World. It is available both in paperback and as a Kindle book.

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