The best way to cool the teapot My professor today in the class made us a question:
"Lets say we have a teapot with water in it.The water is hot.Now we want to cool the water.
Will it cool faster if we put an ice cube above the teapot or under the teapot."
My answer was the it will cool faster if we put the ice cube above it because the warm air stays up and the ice cube will melt faster.
He didn't tell me if I was right or not.
Can anyone help me ?
 A: Open or not open, touching or not touching, ice cube above is better than ice cube below where cooling of the pot is concerned. 
Your choice is correct but it is more accurate to say that air cooled by the ice cube sinks onto the teapot thereby cooling it (note that this mechanism cannot occur if the cube was under the teapot). This isn't a question about which is the best position to melt an ice cube (the answer to that would still be the same though) so it is not relevant to talk about what happens to the ice cube.
If the ice cube was allowed to touch the pot, then the correct answer is still on top of the teapot. The same idea of convection applies but now to liquid in the pot rather than air around it.
A: Put the ice cube atop.  Poorer air and water conductive and convective heat transfer kinetics are more than compensated by meltwater and cooled air dribbling down the pot, further cooling it by heat capacity as they warms from 0 C.  If the ice cube is touching the bottom, meltwater and cooled air flow away from the pot.
