Question

Two cups of coffee, one that is at 10°C and one that is at 20°C, are mixed. Which statement about the temperature of the mixture is correct? There is no kinetic energy transfer so the temperature of the coffee in the warmer cup is the final temperature. The kinetic theory dictates that the temperature of the coffee in the cooler cup is the final temperature. Energy is transferred from faster moving molecules to slower moving molecules, and the result is the average of 15°C. Energy transfer occurs as the molecules collide, and the result is additive; the final temperature is 30°C.

Answer 1

The option c is correct.i.e. Energy is transferred from faster moving molecules to slower moving molecules, and the result is the average of 15°C.
The coffee with higher temperature i.e. 20°C has molecules with high kinetic energy and they move faster than the coffee molecules at 10°C. Thus when they collide, energy transfer takes place and the temperature drops down to in less than 20°C, but greater than 10°C.

Answer 2

I would say that energy is transferred from the faster moving molecules to the slower moving and that the final temperature will be 15 degrees C or the average of the two. The coffee at 20 degrees C will have the faster moving molecules and the coffee at 10 degrees C will have the slower moving molecules.