Question

Which of the following methods would reduce the temperature of hot tea?
(A) Add more tea at the same temperature
(B) Add water at the same temperature
(C) Add water at temperature lower than the temperature of tea
(D) Add water at temperature higher than the temperature of tea

Answer 1

Hint : Temperature is an intrinsic property. Hence it is independent of the volume of the substance. Thermal energy can only flow as a result of temperature difference.

Complete step by step answer
The temperature of a hot tea is to be reduced, how exactly should that be done based on the options provided
Let’s investigate the options one after the other.
A. To pour more tea at the same temperature: This technique cannot work because the temperature of a substance is intrinsic, and thus independent of volume, hence, increasing the volume of the tea will not change the temperature.
B. Pouring water at the same temperature would not work either. Two different substances at the same temperature will still not lose heat or gain heat to one another or from one another
C. Adding water at a lower temperature will be the correct answer, as the hot tea will lose its heat to the water, and thus making the mixture at a lower temperature than the initial tea
D. Adding water at higher temperature will only increase the temperature of the tea.
Hence, the correct option is C.

Note
For clarity, heat would not flow in the option B situation, because as it is in the definition of heat, it is only allowed to flow due to temperature difference. Recall that heat (actually thermal energy) is a form of energy transferred from one object to another as a result of the difference in temperature between them. Hence, irrespective of the nature of substance, if the temperature is the same, heat would not flow. Hence the temperature of neither of them will increase or decrease.