A student asked me this today. I understand that salt doesn’t actually melt ice, but lowers its melting temp, but how do I explain this to a child?
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So what happens is that salt lowers the point where water freezes.
So when you’re making your ice cream usually you take like ice made from tap water and you put the ice cream mix in like a mixer or something above the ice. The ice has a lot of holes and gaps as it doesn’t totally fill the space evenly meaning there is a lot of surface area of the mixer not being touched by the ice.
So heat only transfers from the warmer object to the colder object but that doesn’t work very well when there is low contact surface to actually transfer that heat. So you melt the ice with the salt, the water still has the same temperature as the ice but now fills in all of the gaps from the ice which helps to make the heat transfer more conductive and therefore faster
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