When water is heated in an insulated container and reaches thermal equilibrium with its surroundings, which of the following statements is true?

• A. The temperature of the water continues to increase indefinitely.
• B. The water and surroundings have different average kinetic energies at equilibrium.
• C. Heat flows from the water to the surroundings even after equilibrium is reached.
• D. The temperature of the water becomes equal to the temperature of its surroundings.

Answer: (D)

Verified step by step guidance

1. Understand the concept of thermal equilibrium: When two systems are in thermal contact and no net heat flows between them, they are said to be in thermal equilibrium.
2. Recall that temperature is a measure of the average kinetic energy of the particles in a substance. At thermal equilibrium, the temperatures of the systems must be equal, meaning their average kinetic energies are equal.
3. Analyze the options: The temperature cannot continue to increase indefinitely because that would violate the principle of energy conservation and thermal equilibrium.
4. Heat flow occurs from the hotter object to the cooler one until their temperatures equalize; after equilibrium is reached, there is no net heat flow between the water and surroundings.
5. Therefore, the correct statement is that the temperature of the water becomes equal to the temperature of its surroundings at thermal equilibrium.