Question

A 100 gram copper ball is dropped into a large container of liquid nitrogen until the nitrogen stops bubbling. Then the copper ball is taken out of the liquid nitrogen and placed in a glass of room temperature (25 degrees C) water. If there was 0.3 kg of water in the glass, isolated from the environment, what will be the eventual equilibrium temperature of the ball and water? Build an energy interaction diagram.

Answer 1

SOLUTION:

Energy interaction diagram:

We know that liquid nitrogen exist at a temperature of -196^oC.

When 100 g copper ball is dropped into a large container of liquid nitrogen, heat from the copper ball will be transferred to liquid nitrogen until the copper ball reaches a equilibrium temperature of -196^oC (then bubbling stops).

Now the temperature of copper ball is -196^oC.

Now, when the copper ball at -196^oC is placed in a glass of water at room temperature (25^oC), heat from the water will be transferred to copper ball until the copper ball and water system reaches a equilibrium temperature of T.

That is heat lost by water is the heat gained by the copper.

Hence, We can formulate a equation:

Substituting corresponding values:

Let's forget the units for a while for the sake of solving for T.

That is the final temperature of the system will be 18.4^oC