Properties of salt to melt or freeze qustion

Factual Questions
1

Seems I knew this once,but can’t recall or find the answer.

Salt is spread on roads and driveways to melt ice and works well. Also, salt is mixed with ice in an ice cream maker to freeze the cream.

Howzat work?

2

The salt makes the freezing temperature of water lower, so the water has to be colder in order to freeze. If I spread salt on my steps to melt the ice, and it’s very cold outside, the best I can hope for is better traction, because the ice isn’t going to melt. OTOH, if it’s at or around freezing, the ice’ll melt.

Which reminds me, I’ve got to get some rock salt for the steps and sidewalk.

Robin

3

As for ice cream, the same principle applies. By lowering the freezing temperature, the cannister with the cream is surrounded by very cold water/slush which makes contact with the entire surface, as opposed to chunks of ice which would only have intermittent contact.

4

In addition, the ice is colder than 0 C, sometimes by quite a bit, and so the brine can be quite a bit colder than the freezing point and still remain liquid.

5

Thanks, folks. Now I know.

6

And knowing is half the battle. GI JOOOOOE!!!