How does salt melt fresh water ice, but still make the resultant liquid cold enough to freeze ice cream ?

As in an ice cream maker at home: you add ice cubes from your fridge and salt; it soon becomes a slurry; it freezes your ice cream.How does salt melt fresh water ice, but still make the resultant liquid cold enough to freeze ice cream ?
Salts make the freezing point of water sub-zero which is lower than freezing point of pure water , so it melts the ice but when you expose this slurry to ice creams , the slurry is below the normal freezing temperature and freezes the ice cream !





This is why impure water like solids dissolved sea waters don't freeze even much below zero temperatures, it is just because of salt , which changes the freezing point of water !How does salt melt fresh water ice, but still make the resultant liquid cold enough to freeze ice cream ?
When salt chemically mixes with the water, the freezing point of the resultant liquid is a fair amount lower than just plain water. In fact, the new freezing point of salt water is around 0掳 Fahrenheit. In other words, water can be about 32掳 F colder with salt in it than without.





Just as a side note, the Fahrenheit scale, like the Celsius scale, is based on specific reference points. 0掳 is the freezing point of an ammonium chloride/water mixture (ammonium chloride is a salt), 32掳 is the freezing point of fresh water and 96掳 was normal body temperature. He defined the latter two as 64掳 apart so he could divide the area on his thermometer in between them by 2 six times (2^6 = 64) and have exact measurements. The scale was later recalibrated to more easily convert to Celsius, which is why the standard body temperature is now 98.6掳 instead of the original 96掳. Interesting...

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