Second law of thermodynamics

Definition

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. It implies that natural processes increase the overall disorder or randomness of a system.

5 Must Know Facts For Your Next Test

1. Entropy tends to increase in spontaneous processes.
2. Heat cannot spontaneously flow from a colder body to a hotter body.
3. The second law introduces the concept of irreversibility in natural processes.
4. It explains why perpetual motion machines of the second kind are impossible.
5. The second law is fundamental in understanding energy efficiency and heat engines.

Review Questions

• What does the second law of thermodynamics say about entropy?
• Why can't heat flow spontaneously from cold to hot objects according to this law?
• How does the second law relate to the concept of irreversibility?

Related terms

Entropy:

A measure of the disorder or randomness in a system, often denoted by $S$.

Heat Engine:

A device that converts thermal energy into mechanical work, operating between two heat reservoirs.

Irreversible Process: A process that cannot return both the system and its surroundings to their original states without changes elsewhere.