Is entropy always negative?
Entropy is the amount or the measurement of the energy ( heat) stored/transfered in a thermodynamic system, during changes and the way in which heat is transfered from one substance to another. Therefore, entropy cannot be negative.
If the amount of heat emitted is more than the heat absorbed then the total entropy is negative. So total entropy can be negative and in negative entropy a reaction becomes non-spontaneous.
Hence, entropy is always positive.
A process in which the rate of entropy generation is always zero is a reversible operation whereas irreversible processes lead to a high rate of entropy production. Hence entropy generation is always positive within a system.
Entropy is the measure of disorders in a system. As everything in the universe tends toward a more disordered state so entropy is always increasing. According to the 2nd law of thermodynamics, the entropy of the universe for spontaneous processes is always increasing. So the overall entropy can never be negative.
The entropy of an isolated system during a process always increases, or in the limiting case of a reversible process remains constant (it never decreases). This is known as the increase of entropy principle. The entropy change of a system or its surroundings can be negative; but entropy generation cannot.
A positive (+) entropy change means an increase in disorder. The universe tends toward increased entropy. All spontaneous change occurs with an increase in entropy of the universe. The sum of the entropy change for the system and the surrounding must be positive(+) for a spontaneous process.
According to the second law of thermodynamics, the entropy of the system, i.e., the disorder can never be negative it can be either positive or zero. For a reversible process, the change in entropy is zero because of the increase in entropy when the process moves forwards, and then it decreases when it moves backward.
Answer and Explanation: No, a substance can never have a negative entropy.
However, unlike enthalpy of formation values, all standard entropy values are positive, because the absolute zero for entropy is the most ordered possible state.
Can entropy ever be zero?
If there is no difference in the final and initial state of entropy then entropy will be zero. Devices with a steady state of flow of energy like nozzles, and turbines have zero entropy. Reversible processes also have zero entropy.
We can assess the spontaneity of the process by calculating the entropy change of the universe. If ΔSuniv is positive, then the process is spontaneous.
For entropy, delta S is basically a measure of the change in order/disorder of the reaction. Increasing order gives us a negative delta S value, and decreasing order gives a positive delta S value.