Which of the following indicates that thermal energy is no longer being transferred from boiling water to a mug?

• A. The mug feels warmer than the boiling water.
• B. The temperature of the mug and the boiling water become equal.
• C. The temperature of the mug remains lower than that of the boiling water.
• D. The boiling water stops producing steam.

Answer: (B)

Verified step by step guidance

1. Understand that thermal energy transfer occurs from a higher temperature object to a lower temperature object until thermal equilibrium is reached.
2. Recall that when two objects are in thermal contact, heat flows from the hotter object to the cooler one, causing the cooler object's temperature to rise.
3. Recognize that thermal energy transfer stops when both objects reach the same temperature, meaning no net heat flow occurs.
4. Apply this concept to the boiling water and the mug: heat will transfer from the boiling water to the mug until their temperatures are equal.
5. Therefore, the indication that thermal energy is no longer being transferred is when the temperature of the mug and the boiling water become equal.