Winter is a great time to explore the principles of chemistry through experimentation!
This simple experiment will help your students to see how salt changes the freezing point of water.
Let's dig in...
In this activity, your students will learn about the freezing point of water and how it can be affected.
For this demonstration, you will need 3 cups, water, food coloring, and salt. You will also need an instant-read thermometer if you have older students. (NOTE: The meat thermometer from your kitchen can work well for this.)
NOTE: If your students are older, have them measure and record the temperature of the 3 cups initially and each time they check the cups.
The students should see that cup #1 and cup #2 freeze at the same time, while cup #3 to quite a bit longer to freeze. In fact, they may see that cup #3 does not even freeze in the allotted 3 hours.
If the students measured the temperatures of each cup, they should see that all 3 cups were around the same temperature each time.
Salt lowers the freezing point of water. This means that water with salt in it will remain a liquid for longer than plain water because the point at which salt water will freeze is lower than 32oF.
Food coloring has no effect on the freezing temperature of water, so it will freeze at the same temperature as the plain water.
Once all of your cups have frozen, have the students take them out of the freezer and see which one melts the quickest. You can do this by setting each cup on the counter or by heating them in a pan.
The students should see that cup #3 (the one with the salt) melts quicker, for the same reasons in the explanation. This is why we use salt to melt ice on the driveway during the winter.
We trust that this activity will serve to make chemistry loads of fun in your homeschool. But we also know that it never hurts to have a few more ideas in your homeschooling bag-o-tricks!
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