Which statement best describes the direction of heat flow when water at 5°C is exposed to air at 21°C?

• A. Heat will flow from the air to the water.
• B. No heat will flow between the air and the water.
• C. Heat will flow from the water to the air.
• D. Heat will flow in both directions equally.

Answer: (A)

Verified step by step guidance

1. Understand the concept of heat flow: Heat always flows spontaneously from a region of higher temperature to a region of lower temperature until thermal equilibrium is reached.
2. Identify the temperatures involved: The water is at 5°C and the air is at 21°C, so the air is warmer than the water.
3. Apply the principle of heat transfer direction: Since the air is warmer, heat will flow from the air (higher temperature) to the water (lower temperature).
4. Recognize that heat flow will continue until both the air and water reach the same temperature (thermal equilibrium).
5. Conclude that the correct description of heat flow is that heat will flow from the air to the water.