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And if you work out the energetics as we've gone with thermochemistry, dH you discover there's a huge negative delta H.
如果你计算能量变化,就像在化学热力学中所作的一样，你会发现很大的负的。
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And we can actually better visualize this if we plot how that energy changes as a function of internuclear distance.
而我们就能更清楚地看到这些，如果我们画出,能量随核间距的变化曲线。
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Hess' Law states that for any chemical reaction, the energy change is path independent.
盖斯定律表明，对于任意化学反应，能量变化并非是路径依赖的。
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Now, I know how to relate the heat flow to temperature change, through the heat capacity.
现在我知道怎样把能量的流动,和温度的变化联系起来，通过热容。
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So if we have a negative change in energy for any reaction as it's written, what that actually means is we're giving off energy as the reaction proceeds.
如果我们像这里写的这样,在任何一个反应过后，得，到的能量变化为负值,这就意味着我们在这个过程中放出了能量。
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And we haven't talked about reactions at all yet, so you don't need to worry about the specifics of that exactly, but just that if you have this negative change in energy, you have a more stable product than you do reactant.
当然我们还没有开始讨论反应，所以你不用担心它的细节是怎么样的，你只需要知道，如果能量的变化是负值，那么你将得到一个比反应物更稳定的生成物。
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That is to say I can now reroute that sodium plus chlorine reaction and go a different way, but I still end up with the same change in energy.
也就是说，我可以重新定义一种,钠与氯的反应途径,从另一种途径来实现反应，但是能量的变化过程相同。
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Energy may be favoring reaction in one direction, toward let's say products that have lower energy.
能量上的变化可能支持反应，向着产物具有更低能量的方向进行。
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So, if we took the case of nitrogen, if we add an electron to nitrogen and go to n minus, we find that the change in energy is 7 kilojoules per mole.
如果我们以氮为例，如果我们给氮增加个电子令它变成-1价的氮，我们会发现能量的变化是，7，千焦每摩尔。
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If you have an isobaric you're going to have to calculate where the energy changes, and that's a calculation that's likely on the homework and very like on an exam as well, too.
在等压过程中,我们需要计算能量的变化，我们在作业,和考试中,就会遇到这类问题。
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The boundary is impervious to transfer of heat like a thermos Anything that happens inside of the thermos is an adiabatic change because the thermos has no connection in terms of energy to the outside world.
边界不能传递热量,像热水瓶一样,热水瓶里发生的任何事,都是绝热变化,因为热水瓶与外部世界,没有能量方面的联系。
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You just change volume to pressure and basically you're looking at enthalpy under a constant -- anything that's done at a constant volume path with energy, there's the same thing happening under constant pressure path for enthalpy.
可以看到这就是把体积换成了压强,一般我们都是在一种恒定状态下,考虑焓的，任何在恒容条件下,能伴随能量变化的东西，也在恒压条件下伴随焓同样地变化,所以你可以经常。
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And the change in energy for this reaction is negative 349 kilojoules per mole.
然后得到这个过程的能量变化为,负的，349，千焦每摩尔。
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It only cares what temperature is. If temperature is constant, there's no change in energy.
如果温度是常数,能量就没有变化，对理想气体。
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The sum of path number 2 and path number 3 get me to the same place, so the energy change by going through this time path, this intermediate point here back all the way to final state should be the same the red path.
而经过路径2和3可以3,到达同样的末态，因此经过路径,2和3带来的能量的变化，与路径1带来的,能量变化相同。
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So, we were talking, however, about energy in terms of electron affinity, so we can actually relate electron affinity to any reaction by saying if we have this reaction written as here where we're gaining an electron, we say that electron affinity is just equal to the negative of that change in energy.
但是，我们现在讨论的能量,是电子亲和能，因，此我们可以将电子亲和能,与任何反应联系起来,只要我们将反应写成这种得到电子的形式，我们说电子亲和能就等于,反应前后能量变化的负值。
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So path number 1 went from i, f let's call this path up here. went to f, and this is how much energy change there was.
从i出发，经过路径1到达，能量的变化是这么多。
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pV So there is an arbitrary set point that needs to be defined, right? Because what you actually measure in the lab are changes in enthalpy, just like what you measure when you look at energy change of some sort, you measure the change in energy, right.
焓也是一样，焓是U加,所以需要定义一个任意的设定值,对吧？因为实际上你在实验室里,测得的是焓的改变,就像你在研究某种能量变化时，所测量的那样，你测量的是能量的改变，对吧。
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You're always wasting energy into heat somewhere when you dochange that involves mechanical change.
当进行与机械运动有关的变化时,总会有能量变成热量而被浪费掉。
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And the energy changes, it goes up.
能量发生变化，增加了。
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