4. The Second Law of Thermodynamics

4. The Second Law of Thermodynamics

Concept Explanation:

The second law of thermodynamics introduces the concept of entropy, a measure of the disorder or randomness of a system. It states that in any energy transfer or transformation, the total entropy of an isolated system can never decrease; it either increases or, in the ideal case, remains constant.

This law implies that natural processes tend to move towards a state of greater disorder or randomness. It also explains why some energy transformations are not 100% efficient and why heat naturally flows from hot objects to cold objects, but not the reverse.

Example Problem:

Explain why it is impossible for a refrigerator to cool a room by leaving its door open.

Solution:

When a refrigerator operates, it transfers heat from its interior to the surrounding environment. Leaving the door open does not cool the room because the refrigerator's motor, which is now working harder, generates additional heat that is released into the room. According to the second law of thermodynamics, the total entropy of the room increases as the motor works harder and releases more heat. This increased entropy reflects the fact that the heat removed from the refrigerator’s interior is more than offset by the heat generated by the motor, ultimately making the room warmer rather than cooler.