When ice is melting, we know that the temperature stays constant at 0 ℃. If we were to place ice at 0 ℃ in a sufficient amount of water at ambient temperature, would the temperature of the water itself also stay constant during the time the ice is melting, or is it only the temperature of the ice that stays constant? Does the actual cooling of the water occur after or during phase change?

  • $\begingroup$ If temperature of water stayed constant, where in the world the heat would be coming from? $\endgroup$ – Ivan Neretin May 23 '16 at 5:44
  • $\begingroup$ But constant temperature does not imply that there is no temperature difference (between the ice and water). There is still a temperature difference, but my question is whether this difference remains constant or not. $\endgroup$ – Yasmen Quandil May 23 '16 at 5:48
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    $\begingroup$ See, there is a substantial amount of heat transferred from water to ice. In effect, you are asking whether water can give off heat, while staying unchanged at constant temperature. I wish it would; then we would not need heaters in the winter. $\endgroup$ – Ivan Neretin May 23 '16 at 6:00

No, as the ice is melting, the water is cooling down. Ice melts in water because the water molecules in solution collide with those in the ice, giving them energy. In exchange, the water molecules in solution slow down a little during the collision. While the Ice does not change temperature as it is melting, the energy from the water is going into breaking the crystal structure of the ice, turning it into water. This process consumes energy, and the energy to fuel this process comes from the water in solution. Another factor to consider is conservation of energy - if energy is being put into breaking the ice, where else could that energy come from but from the water?


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