Question

You add 500 mL of water at 10°C to 100 mL of water at 70°C. What is the most likely final temperature of the mixture?

Answer 1

Would it not be the weighted average of the two temperatures....?

Explanation:

Suppose we knew of heat capacities (and we don't here because you have not quoted any). In a problem like this would we not expect that the final temperature is the WEIGHTED average of the two temperatures, according to the mass of each volume?

`(500*mLxx10""^@*C+100*mLxx70""^@C)/(500*mL+100*mL)=20""^@C`.....

Anyway, you should check your text for a more sophisticated approach. But note that this calculation is quite amenable to a simple experiment, given a couple of beakers or polystyrene cups, and a thermometer. What did you find in the experiment?