GRAND RAPIDS — Even though it has felt like winter this week the calendar says we are in spring, but think back to the ice and freezing temperatures. Do you know why the salt on the road melts the ice? In today's weather experiment we are going to discover freezing point depression! Check it out here is what you need.
What you need:
-containers with frozen water
-food coloring (optional)
-cookie pan with sides
Step 1: Overnight freeze water in multiple different containers
Step 2: Loosen the ice from container and set in baking sheet
Step 3: Add salt to ice and watch it melt away
Step 4: Add food coloring in the hollow stalactite like holes and see where the color goes. This step is optional but can be fun!
We have just lowered the freezing point and caused freezing point depression! The salt that we sprinkled on the ice helped lower the freezing point or increased the ice’s ability to melt at a lower temperature. We all know water freezes at 32 degrees Fahrenheit but by using the salt that freezing point gets lowered and forces that ice to melt and prevents the water from freezing or re-freezing. So instead of the ice freezing at 32 degrees now when the salt is added it won't freeze until the temperatures drops closer to around 15 degrees or so.
The salt dissolves on the surface of the ice and creating a brine or a salty water mixture with the molecules on the surface of the ice. That brine is what lowers the freezing point and makes it harder for the water molecules to stick together and freeze.
In the winter road commission crews use a mixture of things on the roads but salt is typically apart of their road treatment mixtures for this very reason. Since ice and snow are mainly made up of water the salt combines and dissolves with that water and helps to start the melting process. This combination creates the freezing point depression we just created!
So there you have it! We lowered the freezing point! Send our meteorologist Candace Monacelli your pictures doing this experiments at home! She will feature future meteorologists on my Facebook page daily!