The mixing of water and changes in temperature?

Question

What will the temperature be of 165 mL H2O at 22 C mixed with 85 mL H2O at 82 C? How do you get this?

Answer 1

Thermal capacity of liquid water is approximately independent of temperature. That means the energy to raise 1ml water 1C is the same as the energy gain by lowing 1ml water 1C. You may consider the high temperature water first passes its "extra" energy to the low temperature water, and then two portions of water with the same temperature mix together. Let the final temperature to be T:
(T-22)*165 = (82-T)*85
Solve this equation we may get T = 42.4(degree C)