On the 2nd Day of Christmas Science, my mommy made with me…Frosty The Snow-Can!
For our second day of science, I wanted to explore something that we desert dwellers don’t get to see very often… frost! I learned that we could explore making frost right in our kitchen, with just some water, salt, and a can! Of course, we also needed to learn a little bit about salt and how it interacts with liquid water, ice, and the freezing points of these materials! But first, let’s the activity!
A clean tin can
Empty your can and thoroughly clean it. Then, use your scissors, googly eyes, construction paper, and glue, to decorate your can so it looks like a snowman!
Fill your can halfway with crushed ice, and add 2 Tbsp of salt to the surface of the ice.
Pour just enough water into your can to cover the ice. Don’t fill it too much, you just want to create a small water layer over your ice.
Set your can in a cool, dry place, and observe your can over the next 30 minutes. It doesn’t take long for crystals to begin forming! Once you see some crystal growth, take a look at them through your magnifying glass! What kinds of crystal formations can you see?
After about 30 minutes, you should have a nice big layer of frost on the bottom of your can! Take a look at them through your magnifying glass. Do the structures of the crystals look different? Are they bigger or smaller than they were before?
When you added the salt to your ice and water, it lowered the melting point of the ice! This caused the ice to melt, while the temperature of the water remained below the freezing point of water. Even though the water was in liquid form, it was cold enough to have frozen solid, had the salt not prevented it!
With the temperature of the can remaining at below freezing, this allows the water vapor in the air to cool and condense on the can. You initially saw this as “dew” building on the can, and it’s the same process that causes dew to form outside on a cool morning! Water vapor is always present in the air as invisible water droplets in the atmosphere. It’s only when it touches a surface that is cooler than the surrounding air that it condenses into dew drop that you can see, just like on your can!
If the surface of the object is very cold, as in the case with your can sitting at a temperature well below freezing, that condensed water will begin to crystallize into small ice crystals! This is how frost forms outside as well, when surfaces are colder than the point of freezing, and water vapor from the air condenses and freezes onto it.
Take it Further!
When we were finished with our snow-can, we wanted to take a closer look at our frost, to see if we could see the ice crystals that had formed while freezing….
We put a slide in the freezer for a couple of minutes and then used it to scrape some frost off the side of our can. We ran over to our microscope so we could catch a peek at the crystals before they melted. What we found was both fascinating and beautiful!
Here we get to see the solid crystal structures of the ice as they had formed on the frost! While these structures were beautiful, we also got to see them expand and melt as they returned to their liquid state! We were able to observe matter changing states right before our very eyes!
This was a fantastic holiday science activity for us to do. Kat made the most adorable little Frosty The Snow-Can I’d ever seen and it only took about a half hour to go from liquid to solid and, through the microscope, back to liquid again!
While we may not be able to build a real snowman anytime soon, the fact that we can create one in our kitchen whenever we want can brighten even the coldest of days!