Final answer:
When water is replaced with ethanol in a calorimetry problem, the equilibrium temperature will move closer to ethanol's initial temperature because ethanol has a lower specific heat capacity than water, resulting in a larger temperature change for the same heat transfer.
Step-by-step explanation:
If water is replaced with ethanol, which has a lower specific heat, the equilibrium temperature will move in the direction of the ethanol's initial temperature. This is due to ethanol having a significantly lower specific heat capacity compared to water. While water's specific heat capacity is approximately 4.18 J/g°C, ethanol's is about 2.44 J/g°C. So, when two substances at different temperatures come into contact, the substance with the lower specific heat will undergo a larger temperature change for the same amount of heat transfer.
Considering a calorimetry problem where bodies are brought to a common temperature, it is the higher specific heat capacity of water that keeps it closer to its initial temperature when it exchanges heat with a body of a different temperature. For example, in a large body like a lake, water's high specific heat means it can absorb or release large amounts of heat with minimal temperature change, maintaining thermal stability over short periods like a day, even with significant air temperature changes.