Science
What is Entropy?
Entropy is a measure of disorder — the number of ways a system can be arranged. The second law of thermodynamics says entropy tends to increase, which is why heat flows from hot to cold and things naturally tend toward disorder.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains entropy.
Key things to understand
- 1It measures how spread-out or disordered energy and matter are.
- 2Second law of thermodynamics: the total entropy of an isolated system never decreases.
- 3It explains why heat flows hot→cold and why perpetual motion is impossible.
- 4It gives time a direction — the 'arrow of time'.
Frequently asked questions
- What is the second law of thermodynamics?
- In an isolated system, total entropy tends to increase over time as usable energy disperses.
- Does entropy mean everything becomes messy?
- Roughly — without added energy, systems drift toward more probable, more disordered states.
- How is entropy related to time?
- The steady increase of entropy gives time a one-way direction, often called the arrow of time.