Which statement aligns with the second law of thermodynamics?

Which statement aligns with the second law of thermodynamics?

• A. Heat flows spontaneously from hot to cold.
• B. Heat flows spontaneously from cold to hot.
• C. Heat flows equally between hot and cold.
• D. Entropy decreases in an isolated system.

Answer: (A)

The second law describes the preferred direction of heat transfer and the tendency for entropy to increase. Heat flows spontaneously from hotter to colder bodies because this arrangement increases the total entropy of the system and its surroundings. In practical terms, a hot object will give up heat to a cooler environment on its own, rather than the cooler environment transferring heat to the hotter object, unless external work is applied. The idea that heat would flow from cold to hot would imply a decrease in entropy for an isolated system, which the second law forbids. Likewise, heat flowing equally only makes sense when the temperatures are equal, and the notion of entropy decreasing contradicts the law. So the spontaneous flow from hot to cold best matches what the second law predicts.

The second law describes the preferred direction of heat transfer and the tendency for entropy to increase. Heat flows spontaneously from hotter to colder bodies because this arrangement increases the total entropy of the system and its surroundings. In practical terms, a hot object will give up heat to a cooler environment on its own, rather than the cooler environment transferring heat to the hotter object, unless external work is applied. The idea that heat would flow from cold to hot would imply a decrease in entropy for an isolated system, which the second law forbids. Likewise, heat flowing equally only makes sense when the temperatures are equal, and the notion of entropy decreasing contradicts the law. So the spontaneous flow from hot to cold best matches what the second law predicts.