Learn about Advanced Placement Chemistry, Thermodynamics 1, in this comprehensive video by bannanaiscool.
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Male Speaker: Okay, why this is reaction happened? See, that's a great question. Why does it react, we can tell a lot about this reaction in terms of how it happens and what's happening, some times who it's happening too, but why does it happen. Well, it has to do with spontaneity and entropy; we have to talk about those things. 52 playing cards randomly distributed in a part okay, here is what I want to do, I want to be able to collect everyone of these cards in this order, Ace through King, diamonds, hearts, spades, clubs now how many different ways are there to do that operation, well only one but how many ways could I actually pick up these 52 cards and put them in a certain order, 52 factorial ways is 52 times 51, 50, 49 -- has a lot of different way this gazillion isn't. So here is the thing, nature actually spontaneously tends towards in any kind of process the most disorder stay possible because it actually has the most probabilities in existence. You see if I were to actually implement energy in order in these cards only one way, will it be a lot of energy that has to be put into this system. But in order to just organize them in any old ways in 15 terms of 52 cards, well, that wouldn't require as much energy. So nature wants to spontaneously go towards those process which required a least amount of energy to able to do. So let's start, no okay that's so good, lets start again, now let us start again, how long we are going to be here, that's a O it's a diamond, and then oh pretty much done, now lets start over again. That could be here a while to be a here a lot of time. Scientist first wonder, okay why is this reactions spontaneous, so some of them said you know what a lot of spontaneous process having corner, the fact that they are exothermic, see a fact that when the reactants get together and form the products there is a lowering of potential energy, energy is released, and so may be that's the driving force, that's the driving force for a spontaneous reaction, well you know what, its true that this has a negative delta H value and that actually it helps to determine whether its spontaneous but you know if you take water, as lets say a solid and you want to turn in into water as a liquid, what the delta H for that reaction that's reactions phase change, the delta H is actually 6.03 kilo joules positive. So you guys saying all over that reaction doesn't happen, because it's a positive delta H, right, now water solid does turn into water liquid in temperatures over 0 degree celsius on this planet, that's a spontaneous reaction to given certain conditions is always this but what's exothermic and what's endo thermic, so thermicity doesn't necessarily tell you if your reaction is spontaneous or not. Entropy is the driving force to all spontaneous reactions of the planet and entropy is just this, its the measurement of the degree of a randomness, that's present, the first law of thermodynamic tells us that energy can be created or destroyed is just kinds of converted from one form to another well, the second law of thermodynamic talks about entropy, the entropy of the universe is increasing, and every spontaneous process that happens, happens to increase the randomness of the universe that's the second law of thermodynamics.