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When pouring something on ice, like deicing salt or vinegar, to make it melt at a lower temperature, does the energy required to melt it change (in a significant way)?

Edit: I am only interested in the energy required for the phase change (i.e. melting), not the energy required to reach 0,1 °C (or something like that).

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  • $\begingroup$ For the example of putting salt on ice, you are still melting pure ice (no salt in it). In my opinion, the answer for this example is "no". $\endgroup$ Oct 25, 2020 at 21:43
  • $\begingroup$ @DavidWhite But somehow the salt must mix with the ice, otherwise there wouldn't be an effect, would it? Maybe some weird surface physicial chemistry or so? $\endgroup$
    – d-b
    Oct 25, 2020 at 22:26
  • $\begingroup$ Salt is often used to melt ice and snow on steps and roads. $\endgroup$ Oct 26, 2020 at 1:06
  • $\begingroup$ @d-b, yes, I realize that, but I distinctly remember that your particular question did NOT come up in my physical chemistry class many years ago. That is why I gave an answer that I labeled as an opinion. $\endgroup$ Oct 26, 2020 at 17:42

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In the situation where you have to raise the solution's temperature to < 0 C for it to liquify, rather than to raise the temperature of the same mass of pure water all the way up to 0 C , then it will take less energy if all other conditions are the same. However the liquid solution that required less heat to reach its melting point will still be colder than the liquid water just after their phase changes.

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  • $\begingroup$ To be clear, I am only interested in the energy required for the phase change. $\endgroup$
    – d-b
    Oct 25, 2020 at 22:51
  • $\begingroup$ Phase change occurring at a lower temperature requires less energy. $\endgroup$ Oct 26, 2020 at 1:04
  • $\begingroup$ How much less? Can you source it? $\endgroup$
    – d-b
    Oct 26, 2020 at 8:46
  • $\begingroup$ @AdrianHoward, you are incorrect regarding your phase change assertion. I know for a fact that when you boil water at less than atmospheric pressure, the heat of vaporization goes up even though the boiling temperature goes down. $\endgroup$ Oct 26, 2020 at 17:45
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    $\begingroup$ Fig. 3-12 of Pruppacher's and Klett's Microphysics of Clouds and Precipitation (2004), for example, graphs the increasing latent heat of melting with increasing temperature. See also here. $\endgroup$ Oct 26, 2020 at 21:34

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