If you place a piece of iron at 90 °C into water that is 25 °C, in which direction heat will flow?

Determine the final temperature when a 25.0 g piece of iron at 85.0 °C is placed into 75.0 grams of water at 20.0 °C.

First some discussion, then the solution. Forgive me if the points seem obvious:

a) The colder water will warm up (heat energy "flows" in to it). The warmer metal will cool down (heat energy "flows" out of it).

b) The whole mixture will wind up at the SAME temperature. This is very, very important.

c) The energy which "flowed" out (of the warmer water) equals the energy which "flowed" in (to the colder water)

Explanation:

fe 55.85 g/mol and h2o 18.02 g/mol.