Does liquid water freeze at the same temperature at which ice melts?

Answer 1

I suppose the questioner is wondering whether a quantity of water in solid form (that is, ice) will take longer to turn back into liquid water (that is, to melt) than the liquid water took to freeze in the first place! That is a fascinating question, but it shows a bit of a misunderstanding regarding heat, energy, and heat transfer. Without more info, there's simply no way of answering the question, because there's a lot more involved than just time. An ice cube may take up to an hour to form in the freezer but may melt on the kitchen floor in a few minutes. That gives the impression that water melts faster than it freezes. On the other hand, frost may form on the windshield of your car almost instantly under the right conditions but may take a few minutes to melt after you turn the defroster on. That gives the impression that water freezes faster than it melts. Further, you may have noticed that an ice cube melts much more quickly when placed in a metal sauce pan than when placed in a wooden salad bowl. It all has to do with heat transfer. The faster heat can be drawn away from an object, the faster it will cool down -- and freeze eventually. The faster you can transfer heat to an object, the quicker it will heat up -- and melt eventually.

Answer 2

The question is a good one, and has sever layers of meaning and understanding. The most superficial layer is deals with the most simple interpretation of the question, and the answer becomes: "Because water exists in equilibrium in a solid/liquid matrix at the freezing point, which is also known as the melting point." That is, melting point and freezing point are the same thing. In fact, the answer can become more complicated due to the fact that water can be cooled to below the normally considered freezing point in a phenomenon known as supercooling. Supercooling of water can occur when water is slowly cooled below the freezing point in the absence of a "nucleation point " (a localized point around which a crystal may form). Liquid water, in the absence of ice, can exist at a temperature just below -40°C. Pure water can also be "hypercooled" (not a real word) to form "glassy water" wherein the water becomes amorphous (without crystal formation), at temperatures as low as -180 °C. Glassy water has not truly frozen, and remains a liquid. Finally, impure water can experience "freezing point suppression." The addition of a second substance to water can result in the suppression of the freezing point to below the stander referenced value of 0°C.

Answer 3

Because water and ice it is the same substance only in different phase and phase change happen at a fix temperature whether it is from ice to water or water to ice.

Answer 4

Yes, The freezing point of water is also the melting point of ice.