Calculating entropy

[Peter Nguyen 2I]

Why do we calculate entropy for volume change and temperature change independently?

[Jim Brown 14B Lec1]

If there's a change in pressure/volume, the entropy is dependent on Temperature. If there's a change in Temperature, the entropy is dependent on volume. You've gotta do one before the other or else there's just no calculation (that a 14B student knows how to do, idk about actual chemists).

[Ariel Cheng 2I]

When we calculate the two independently, we are essentially splitting it up into steps which is allowed since entropy is a state function. First we change the volume and then we change the temperature to reach the final form.

[Jonny Schindler 1A]

Once you do each, just add the two to get the total change in entropy

[Mark 1D]

we isolate the two changes in entrophy and then add together

[Maya_Panozzo_2D]

In an equation given in the lecture, it said the change in entropy equals heat(q) rev divided by T. Can someone explain why it's reversible and why that matters?