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Saturday, August 11, 2012

Ice-cream - How Does Salt Ice Freeze our Liquid?




On Friday we hypothesized about salt ice. We had to make ice-cream and then freeze it inside a snap lock bag with ice and salt. We recorded the temperature of just the ice, then after we added the salt, then 15 minutes after time had passed. The results were varied but we concluded that the ice was further dropping in temperature due to the salt that we placed inside the bag.



BUT HOW DOES THIS HAPPEN?

Ice has to absorb energy in order to melt, changing the phase of water from a solid to a liquid. When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands, if you are holding the baggie of ice!). When you add salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was before, which is how your ice cream freezes.

(Source: Howstuffworkz.com)

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