why does salt melt ice but you put it in ice cream to make it freeze faster?

Question

we put salt on roads in winter to melt the ice, but when making homemade ice cream you put salt in the ice to make the ice cream freeze faster.

Answer 1

Fresh water changes state from liquid to ice or ice to liquid a 32F or 0C, but salt water does so at a LOWER temperature. Remember, however, that ice can be much colder than 32F/0C -- that's just the WARMEST it can be and remain frozen. The ice you get from your freezer or by in bags is quite a bit colder than that.

To freeze your sweet, creamy ingredients to make ice cream you need to put it in contact with something cold enough to make it freeze. Unfortunately, while heats transfers quickly to liquid water it transfers poorly to solid water (ice). That means that your ice isn't doing the job it could because it's solid, but if it becomes liquid freshwater you're back to 32F/0C: warmer than you want for the job.

By adding the salt to the ice you are letting the salt convert the ice into saltwater on its surface at less than 32F/0C. By using this very cold saltwater to pull away heat from your ingredients you get your ice cream to freeze more quickly.

Answer 2

Salt on the roads dissolves and lowers the freezing point of the water on the road. The salt used in an ice cream maker is used on the ice on the outside, not in the ice cream mixture. It lowers the freezing point of the ice and that lowers the temp of the ice cream, freezing it. When ice melts it takes energy. This energy is withdrawn from the ice cream mix

Answer 3

Salt doesn't melt ice. Water freezes at 0 Celsius normally. If you add salt to water, the melting point of the water goes under 0 Celsius and so the water/snow on the road doesnt freeze. But it works up to (down to) -4 or -5. And that's why the see doesnt freeze too.
I dont think people add salt to ice cream zo make it freeze faster. I would say it's just because of the flavor.

Answer 4

The function of salt in either case is to reduce the freezing point of water. You spread salt on ice on the road to melt it because the salt reduces the freezing point. You put salt with the ice in the ice cream freezer to force the ice to melt; this reduces its temperature so that it will absorb heat from the ice cream mixture.

Answer 5

The salt in ice cream is in a small amount, what it does actually is 'slightly' melt the ice cream, but then the coldness of the rest of it causes it to freeze in a more solid state. For example, if you put a couple pinches of salt between two separate ice cubes and then put them together, after a little while, the two ice cubes would be frozen together.

Answer 6

the salt lowers the freezing point of water. if it's below -10ºC than nothing will happen. if it's above that temp ice melts. when you put it in ice cream it's effecting the melting point of the ice cream the same way. it doesn't make it freeze faster it makes it set harder, and you need it hard to not have a bunch of mush

Answer 7

you put salt on the ice to make ice cream because just like the roads, it lowers the freezing point so that the ice doesn't solidify; the salt on the ice allow the ice cream barrel to move freely in the ice so that it can transfer the energy (or temperature) to the cream so that it solidifies easier...

Answer 8

adding salt to ice lowers the freezing point, so the ice melts and then to refreeze, heat moves from the ice cream into the salt-ice mixture, freezing the ice cream.

Answer 9

Salting the water in a pot will make it boil faster as well.

Answer 10

Salt is an element with a high density that retains its temperature well. If it is cold, it stays cold longer than other things. If it is hot, it stays hot longer than other things.