Why do you ice cream vendors sprinkle salt on ice before they sell ice cream carts?
Salting ice prior to making ice cream allows the water (from the melted ice) to go below the freezing poing of water (32 F or 0C). If the ice was not salted, then as the ice melts, the water produced would never get colder than (32F or 0C), and as a result, the ice cream would not be able to freeze up as solid as you would normally want your ice cream to be. In essence, it allows you to get your ice cream to a lower temperature than if you had not salted the ice at all. As an experiment, try this yourself with a thermometer, some ice in a large cup, and some salt. You’ll find that when the salted ice starts melting, the water produced will be below the freezing point of water (but the water won’t freeze!). Cool! huh?
