Question

kiki has exactly 1 cup of coffee that is 80°c and 1 cup of cream that is 40° c. what is the best prediction for the temperature of the coffee after the two are mixed? about 80° c about 60° c about 120° c about 40° c

Explanation:

When two substances of different temperatures are mixed (assuming equal volumes here, as both are 1 cup), the final temperature should be a weighted average. The coffee is 80°C and cream is 40°C. The formula for the final temperature \( T_f \) when mixing equal masses/volumes (since same cup volume, we can assume similar heat capacities for simplicity) is \( T_f=\frac{m_1T_1 + m_2T_2}{m_1 + m_2} \). Here, \( m_1 = m_2 = 1 \) (cup, so mass proportional to volume), \( T_1 = 80 \), \( T_2 = 40 \). So \( T_f=\frac{1\times80 + 1\times40}{1 + 1}=\frac{120}{2}=60 \)°C. Also, heat transfers from hot (coffee) to cold (cream) until thermal equilibrium, so the final temp is between 40 and 80, and since equal amounts, it's the average.

Answer:

B. about 60° C (assuming the options are labeled, and the second option is about 60°C)