Entropy
MCAT glossary · Chemical & Physical Foundations of Biological Systems
Definition
A measure of the dispersal of energy and matter, symbol S.
Entropy in plain English
Entropy (symbol S) measures how spread-out and disordered energy and matter are — the more ways things can be arranged and scattered, the higher the entropy. A drop of dye swirling until it evenly colors a whole glass of water is entropy in action: the universe naturally drifts toward messy, spread-out states because there are vastly more ways to be scattered than neatly stacked. That's why a room gets messy on its own but never tidies itself, and why heat always flows from hot to cold. Nature quietly favors disorder.
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