The Second Law of Thermodynamics is one of the most fundamental principles in physics. It states that in any natural process, the entropy—or disorder—of an isolated system will never decrease over time.
What Is Entropy?
- Entropy is a measure of disorder or randomness in a system.
- Higher entropy means more possible arrangements of particles; lower entropy means more order.
What Does the Law Mean?
- In an isolated system (one that exchanges neither energy nor matter with its surroundings), all processes naturally evolve toward a state of maximum entropy.
- For example, if you mix hot and cold water, the temperatures even out. The system becomes more disordered, and entropy increases.
- It explains why certain processes are irreversible—you can’t un-mix milk from coffee or un-break an egg.
Key Implications:
- Heat flows from hot to cold, not the other way around.
- Perpetual motion machines (that create energy without input) are impossible.
- The universe as a whole is moving toward higher entropy—greater disorder.