system
Given the following post, respond as if you're commenting on Reddit:
human
Why does rock salt help with thawing sidewalks, yet it's used in ice cream makers to make the ice cream even colder?

This is something that has absolutely confused me since I was a fetus.
gpt
Here's why: the scientific principle is identical for both purposes. Adding salt to water allows it to remain at the liquid state at a colder temperature, usually the coldest possible temperature is -25 degrees Celcius. The use is obvious for thawing snow or ice in the winter, throw it on the ground and it melts. When it's used in an ice cream maker, they don't put it in the ice cream, but on the ice around the ice cream barrel. This allows more of the water to contact the barrel at a lower temperature, thus increasing the heat transfer rate from the ice cream to the ice when making the ice cream.

Edit: the temperature listed (-25) is a rule of thumb that is used when salting your sidewalk up here in Canada. If it's colder than that, it's considered a waste of time and money to throw salt down.