Here in Minnesota, we see these ice crystals on our window panes numerous times throughout the fall and winter. What exactly are they? Where did they come from? Did Elsa stop by in the middle of the night?
To explain, I want to remind you first about another weather wonder - condensation. On warm summer days, if you have a glass of ice water outside in the heat, water droplets will form on the outside of the glass. This water is actually water vapor (water in gas form) from the air. It forms because the ice water in the glass is lowering the air temperature around the glass and causing the water vapor in the air to condense into liquid form. We sometimes say that "the glass is sweating", but the "sweat" isn't coming from the glass at all but from the air around it.
When the air temperature drops even further than the dew point which causes condensation, water vapor in the air skips the condensation step altogether and goes directly from water vapor (gas) to solid ice crystals.
In summary, here is a recipe of the conditions required for frost to form on your car or house window:
Make your own frost indoors!
What You Will Need:
Making the Frost:
1. Take your glass container and fill it with the cup of ice.
2. Add 2 tbs. of water to the ice and stir together with the spoon.
3. If any condensation forms, wipe it off of the glass with a paper towel.
4. Add your salt to the mixture and stir it together.
5. Observe the glass container for the next 5 minutes or so. Scratch the side of the jar every so often to test if frost is forming.
6. You can repeat this process again with a fan! After adding the salt, place your container about three feet away from a fan. Observe to see if the frost forms more quickly or if the pattern of ice crystals looks any different.
Before you added your salt, the container just “sweat.” Water vapor from the air outside of the jar condensed onto it. When you added the salt, it caused the melting point of the ice to drop below 32 degrees, meaning the temperature of the glass dropped so low that water vapor outside of it skipped the condensation step and turned directly from vapor to solid ice crystals!
So, next time you notice frost on your house or car window, you will not only enjoy its beauty, but you will also be able to say you know how it formed! And, just like Elsa, you can say that you’ve had a chance to make it yourself!