The second law of thermodynamics states that the total entropy of an isolated system can never decrease and is constant only when all processes the system undergoes are reversible.
Entropy can be described as the measure of the disorder of a system or the unavailability of some system energy to do work.
There are more states of disorder than order, so the tendency of systems to move towards disorder is described by probability.
Entropy is a state function and therefore only depends on the current state and configuration of a system, and not how the system reached that state.
Maximum entropy occurs when a system is in thermodynamic equilibrium.
The change in a system’s entropy is determined by the system’s interactions with its surroundings.
Closed systems spontaneously move towards thermodynamic equilibrium.
The entropy of a closed system never decreases, but the entropy of an open system can decrease because energy can be transferred into the system.
The entropy of the universe is always increasing.