Final answer:
The temperature of water at the outlet of a three-way mixing valve is typically an intermediate temperature between the hot and cold inlet water temperatures. If equal masses of water at 20° C and 40° C are mixed, the result is a temperature of 30° C.
Step-by-step explanation:
The temperature of water at the outlet of a three-way mixing valve will most likely be an intermediate temperature between the temperatures of the inlet waters. When you mix water of different temperatures, the result is water at a temperature that is in between the original temperatures of the mixed waters. For example, if you mix equal masses of water at 20.0° C and 40.0° C, the result will be water with a temperature of 30.0° C. In this mixing process, entropy increases, manifesting in the mixing of molecular motion where the faster-moving molecules of the hot water mix with the slower-moving molecules of the cold water, resulting in an intermediate overall temperature.