(BigCountryHomepage.com) – We have made it to our final experiment in the summer series of Kayleigh’s Weather Workshop! Summer is wrapping up and the kiddos are getting ready to go back to school, so it is time for a sweet treat to celebrate all of the “cool” things we have learned this summer. Meteorologist Kayleigh Thomas shows us how to make our own ice cream using science.
In the small sealable bag, place one tablespoon of sugar, a half cup of milk and a quarter tablespoon of vanilla extract. Seal the bag well.
Now, add about four cups of ice to the gallon-sized sealable bag. Add half cup of rock salt to the ice. Take note of what the salt does to the ice.
Place the smaller sealed bag in the gallon bag with the ice and salt. Once the bag is inside, seal the gallon bag tightly.
Put on the oven mitts or wrap the bag in a towel and shake for five minutes. Keep an eye on the smaller bag throughout the five minutes to see what is happening.
What is happening
The science in this tasty experiment really comes in the ice. When you add salt to the bag of ice, the ice melts more than usual and feels much colder. Why is that?
In the winter you probably hear about having to salt the roads before or right after it sleets or snows to prevent water from freezing or refreezing. But when we added salt to our bag of ice, it got colder. It seems a bit contradictory and confusing, but it is all about the freezing point and freezing point depression.
When salt is added to water, it lowers the temperature that water freezes. So instead of freezing at 32 degrees Fahrenheit, it will freeze as low as –5 degrees. The same applies when you add salt to the ice cubes because there is a thin film of water on each cube.
The salt, when dissolved in water, forms into its ions. Basically, it breaks into its individual molecules. With the molecules separated, they make it much harder for the water molecules to crystallize into ice. Therefore, if you want the water to freeze it must be much colder.
So, why does the bag feel colder if the ice is melting? When ice melts, it absorbs energy from the environment around it. In our case energy equals heat. So, the ice is melting, and the salt is dissolving in the water. That water is now mixed with salt and has lowered the temperature at which the water can freeze and form back into ice. The process just keeps going. The ice will continue to melt and absorb heat from the environment making the bag colder than 32 degrees, but it will not be cold enough to refreeze into ice thanks to the salt.
If you have any weather questions or experiments you want to see, send Meteorologist Kayleigh Thomas an email by clicking here