Second law equation

[JonathanS 1H]

Hello everyone
Can someone explain the second law of thermodynamics in relation to the equation (delta)S = q_rev / T? I am confused as to what this equation means in a conceptual sense.

[Alice Chang 2H]

ΔS : change in entropy
q(rev) : heat inputted into the system that is reversible
T : temperature

This equation is a "basic way of evaluating ΔS for constant-temperature processes such as phase changes, or the isothermal expansion of a gas."
So by dividing heat inputted into the system by the constant temperature that the system is held at, you can find the amount of disorder (entropy) of a system.

Hope this helps!

[JonathanS 1H]

I guess my question is more of how does this equation prove that entropy always increases in a system.

[405268063]

I don't think that this equation shows that entropy always increases in a system. I think during the review session today, we were told to use this only for phase changes.