two cups of coffee, one that is at 10°c and one that is at 20°c, are mixed. which statement about the…
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?\no there is no kinetic energy transfer so the temperature of the coffee in the warmer cup is the final temperature.\no the kinetic theory dictates that the temperature of the coffee in the cooler cup is the final temperature.\no energy is transferred from faster moving molecules to slower moving molecules, and the result is the average of 15°c.\no energy transfer occurs as the molecules collide, and the result is additive; the final temperature is 30°c.
Answer
Brief Explanations:
When two substances at different temperatures are mixed, heat (energy) is transferred from the substance with faster - moving molecules (higher temperature) to the one with slower - moving molecules (lower temperature). Assuming equal amounts of coffee in each cup and no heat loss to the surroundings, the final temperature is the average of the initial temperatures. The formula for the final temperature $T_f$ of two substances of equal mass $m$ and specific heat capacity $c$ with initial temperatures $T_1$ and $T_2$ is $T_f=\frac{T_1 + T_2}{2}$. Here, $T_1 = 10^{\circ}C$ and $T_2=20^{\circ}C$, so $T_f=\frac{10 + 20}{2}=15^{\circ}C$.
Answer:
Energy is transferred from faster moving molecules to slower moving molecules, and the result is the average of 15°C.