Hi, I've a few questions about entropy. Entropy is the measure of disorder in universe, and the entropy of universe always increase. So, is saying this correct that entropy is the unusable energy causing the disorder and due to this the amount of useable energy decrease every time when the entropy increase in a process? How entropy was derived from Carnot cycle? When defining entropy, why we use the term reversible process though its a state function? what happens to entropy with change in temperature? As entropy mathematical expression shows inverse relation but I think I'm getting it wrong. Why we use the isothermal condition to define it? Sorry for a long list of questions but I'm really confused about these points. Please need your help. thanks.