If you have a quantity which is constant over any closed path, that quantity is a thermodynamics state function.
如果有一个物理量,对任何闭合回路积分是常数,这个物理量就是一个热力学态函数。
But calculating it alone doesn't necessarily tell us whether or not it will just happened of its own accord.
但是计算这些物理量并不一定能够告诉我们,这些变化是否会自发的进行,而这正是我们想要做到的。
OK, now what we'd like to do is be able to calculate any of these quantities in terms of temperature, pressure, volume properties.
现在我们想要做的是能够利用,温度,压强和体积的性质,计算上面的物理量。
It's related to the heat capacity, the constant volume of heat capacity and something you could measure.
它联系了热能,恒容热容和一些,我们能够测量的物理量。
And that's what led us to a number of results to determine what quantities we even need to be looking at.
这就要求我们考察一系列结果,然后决定到底需要计算什么物理量,来找出。
So, this observation is equivalent to saying that there must be something that is path independent.
这个表述相当于说,一定存在某个物理量是与路径无关的。
Whereas under these conditions, these quantities, if you look at free energy change, for example at constant temperature and pressure, H you can still calculate H.
但是,在这些条件下,这些物理量,如果我们考察自由能的变化,例如在恒定的温度和压强下,我们仍然可以计算。
That tells us the direction of spontaneous change for ordinary processes, chemical processes, mixing and you name it, under conditions that are easy to achieve in the lab.
这个物理量告诉我们在实验室,能够实现的条件下通常的过程,化学过程,混合以及你所能想到的过程,自发进行的方向。
So a reversible process leads to requiring certain quantities to be maximized.
因此可逆过程要求,一些物理量要达到最大值。
There's a zeroth law The zeroth law every one of these laws basically defines the quantity in thermodynamics and then defines the concept.
有第零定律,这些定律中的每一条都定义了,热力学中一个基本物理量的概念,第零定律定义了温度。
That is, in terms of equations of state. For any material Then we would really be able to essentially calculate anything. Anything thermodynamic.
换句话说,利用任何一种物质的状态方程,我们就能够实质上,计算所有物理量,所有热力学量。
And the main points of the latter part of the lecture is what are these quantities?
方程右边的物理量,是什么?
And so that led us to the definitions of other energy quantities, the Helmholtz and Gibbs free energy.
这就要求我们定义,其他的和能量相似的物理量,亥姆赫兹和吉布斯自由能。
Now, the purpose of this exercise is to give you a little bit of practice in figuring out what these quantities are.
就有这样的结论,这个练习的作用时让你们理解,这些物理量是什么。
And this is the familiar result from ordinary mechanics, where you're not worrying about something like entropy for a whole collection of particles.
在普通力学中,如果不关注大量粒子的熵,诸如此类的物理量的话,这就是我们通常见到的结果。
You can still calculate the heat that's released. This is what will tell you under some particular conditions what will actually happen. Where will you end up.
你仍然可以计算放热,在特定条件这些下这些物理量,能告诉我们将会发生的事情。
We could choose any two quantities, and, in fact, it turns out that these are going to prove, after we have the second law, not to be the best choice.
我们可以任选两个物理量,其实,在学习了热力学第二定律之后,我们可以证明,这样的选择并不是最好的。
In other words, we're taking advantage of the fact that we now know that quantity. In the case of the ideal gas we just have a simple model for it.
换句话说,我们可以利用我们已经,了解这个物理量的这个优势,对理想气体我们有一个简单的模型。
Be careful, and this is going to be especially complicated and confusing when we get to quantities that have a more obscure meaning like entropy.
大家要小心,如果需要测量的物理量,如熵,没有很明确的意义,那么着可能变得很复杂。
Things that we can relate to the properties of the substance that we're doing the experiment on.
我们实验对象性质,有关的物理量来表示。
Certainly in principle we know how to calculate this and other stuff for a change in state of this sort, for lots of changes of state.
的确原则上我们可以对某个状态变化,计算这些物理量,或者其他物理量,对其他的变化也可以做相同的计算。
This one turns out to be the heat capacity, and this one turns out to be something that we measure in the Joule-free expansion.
其实,这就是热容,这是焦耳自由膨胀实验中,我们要测量的物理量。
So we have this condition that's established in a quantity that we know how to calculate.
在种种条件下,我们得到了一个我们知道如何计算的物理量。
So here, let's combine these to define a new quantity.
我们把这些结合起来组成新的物理量。
We've formulated one particular kind of engine, and seen how we can analyze what it does, come up with relations that seem of value for efficiency and other quantities.
这是一个很典型的热机,我们来分析它是怎么工作的,然后得到效率和其它一些,有用物理量之间的关系。
So the result is we can combine all of these as a single differential, and just like we've seen before, what that suggests is that we define another new quantity given by this expression.
结果就是我们能把所有的结果,整理成一个单一的微分,就像我们前面看到的一样,这说明我们可以利用这个式子,定义一个新的物理量。
It certainly is, it still is going to be useful to do thermochemistry.
实际上,这样的物理量在化学热力学中是非常有用的。
But it doesn't tell you, by itself, which direction things run in.
但是这些物理量并不能告诉我们,反应朝着那个方向进行。
So, these two quantities, again, are path dependent.
这两个物理量,再次。
All these things though are incredibly practical, useful criteria.
尽管这些物理量,都是很实用判据。
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