When Entropy Is Negative?

Negative entropy

means that something is becoming less disordered. In order for something to become less disordered, energy must be used. This will not occur spontaneously. A messy, or disordered, room will not become clean, or less disordered, on its own.

Can entropy be negative?

The true entropy can never be negative. By Boltzmann's relation S = k ln OMEGA it can be at minimum zero, if OMEGA, the number of accessible microstates or quantum states, is one. However, many tables arbitrarily assign a zero value for the entropy corresponding to, for example, a given temperature such as 0 degrees C.

What does it mean if ΔS is negative?

Negative delta S (ΔS<0) is a decrease in entropy in regard to the system. For physical processes the entropy of the universe still goes up but within the confines of the system being studied entropy decreases. One example is a freezer with a cup of liquid water in it.