In this case, it is the opposite of that of entropy, the negative sign represents a spontaneous process. By finding the sign of it alone we are able to predict whether a phenomenon will happen spontaneously or not. Calculating the net change in entropy is very tedious and hence we devise a new function, called Gibbs Free energy, which is a property of the system and easy to calculate. Net entropy change of a universe is given by $\Delta S= \Delta S_$. Yes, I agree that entropy of the system (water) decreases but it happens that at STP the entropy of the universe (the water and its immediate surroundings) have a net increase in entropy. I reply that you didn't read the statement correctly it is written the entropy of the universe and not of the system. A positive entropy means an increase in disorder. Now you may object by saying that why does water freezes spontaneously at STP? After all the entropy of ice is less than that of water hence there is a decrease in entropy of the system, hence this should not be spontaneous. Generally, the combined entropy of the system and the surrounding for a spontaneous process increases. Whether the enthalpy of the system increases (i.e. 2C(s, graphite) + O 2 o +179 J/K A decrease in the number of moles of gas corresponds to a decrease in entropy (S < 0). The heat that passes into or out of the system during a reaction is the enthalpy change. An increase in the number of moles of gas corresponds to an increase in entropy (S > 0). Enthalpy is a central factor in thermodynamics. A phenomenon will happen spontaneously if the entropy of the universe is positive and won't happen if it is negative or zero (again, spontaneously). Thermodynamics is the study of the relationship between heat (or energy) and work. You need to clear the difference in entropy of the system and the universe. (It’s not a perfect analogy but it serves to show my thinking). Then, the lower energy state would be at the bottom of the well, but then, apparently, with higher entropy. I am seeing the changes of state (in this example) to be like a potential well, where energy needs to be added to move the substance out of the well and change its state. Perhaps I am visualising this problem in the wrong way. losing energy, however, this contradicts the entropy conclusion. If I think of a gas, if would seem to me that a more stable arrangement is becoming a liquid i.e. I am unfamiliar with systems that are more stable at higher energy levels. When ∆S is positive, we are increasing the energy of the system, but apparently also making it more stable. When I see that ∆S is positive for an increase in entropy, that confuses me. My last point was going to be: an increase in entropy is an increase in energy, although this isn’t explicitly stated.
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