A better description of entropy. Second Law of Thermodynamics. Welcome to entropysite. ENTROPY IS NOT "DISORDER" Notice: entropysite.com is now Please update your links and bookmarks. Energy of any type disperses from being localized to becoming spread out*, if it is not constrained. This is the ultimate basis of all statements about the second law of thermodynamics and about all spontaneous physical or chemical processes. * Energy dispersal; energy becoming spread out. In simple physico-chemical processes such as ideal gas expansion into a vacuum , ”spread out” describes the literal movement of energetic molecules throughout a greater volume than they occupied before the process. IMPORTANT NOTE: The initial statement above (about the movement of molecules into a larger volume as solely due to their motional energy) is only valid as a description of entropy change to high school students or non-scientists when there will not be any further discussion of entropy.
A useful approach to microstates for students is here. "motional energy", its meaning. "phase change energy" Entropy Is Simple...If We Avoid The Briar Patches! A Student’s Approach to the Second Law and Entropy. Notice: entropysite.com is now Please update your links and bookmarks. This is written for you quickly to understand the second law and entropy. All but a few general chemistry texts have discarded “entropy is disorder” and adopted my approach. However, if your text and instructor describe things differently, don’t argue with or correct her/him! A Student’s Approach to the Second Law and Entropy The Second Law of Thermodynamics Many texts define the second law as “the entropy of the universe increases during any spontaneous process” and then throw qrev/T or free energy = ΔG and ΔS at you. That’s too complex too fast. The second law is based on human experience. What’s happening in each of those processes?
OK? But what about “entropy” and “universe” that is in so many textbooks and may be in yours? If not, skip down to “What Is Entropy, REALLY?” The rock has potential energy localized in it when you lift it up above the ground. What Is Entropy, REALLY?