David W. answered • 02/01/18
Tutor
4.7
(90)
Experienced Prof
It depends on the convection coefficient and the temperature of the surrounding media.
For example, hot water for coffee or cocoa in a metal cup makes the cup very hot but cools the water. Putting the metal cup of water in a freezer cools it even faster (so PLZ don't put your tongue on a frozen metal pipe).
By contrast, styrofoam or an insulated cup or a glass-lined thermos will keep the water warm for a long time, even in a cool room.
Now, the exposed surface area is an important factor in the equation. If the water in poured onto a large tray, it will cool very quickly. Poured on a large metal tray in a freezer, water would freeze in 10 minutes. Poured into a liquid nitrogen freezer, water freezes instantaneously.
So, convection coefficient, temperature outside insulation, surface area, etc. are important factors.
