To ask questions like how much heat is released in a chemical reaction that takes place at constant temperature.
当我们想要知道,当一个化学反应在恒定的温度下发生时,会放出多少热量时。
And the equation of state, pressure versus volume at constant temperature, is going to have some form, let's just draw it in there like that.
系统的态函数,恒温下压强比体积,变化曲线,就像这样。
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。
And in particular let's look at, for example, du/dV du/dV at constant temperature.
更特殊一点考察,恒定温度下的。
It's a state function, so we're at constant temperature and pressure, and now we want to consider some chemical change or a phase transition or you name it.
这就是态函数,我们处于恒定的温度和压强之下,然后考虑某些化学变化或者相变,或者你想考虑的东西。
dS/dV And that, now, we know must equal dS/dV, with a positive sign. At constant temperature.
我们知道这个等于恒定温度下的,符号为正。
There's our condition for equilibrium at constant temperature and pressure.
这就是我们在,恒定温度和压强下的平衡条件。
SdT This has minus T dS minus S dT, but the dT part is zero because we're at constant temperature.
这一项包含负的Tds和,但是dT的部分等于零,因为温度为常数。
dS/dV There's some variation, dS/dV, at constant temperature.
这里有一点变化,即恒定温度下的。
dG/dp And this is dG/dp at constant temperature.
这是恒定温度下的。
In other words, the order of taking the derivatives with respect to pressure and temperature doesn't matter And what this will show is that dS/dp dS/dp at constant temperature, here we saw how entropy varies with volume, this is going to show us how it varies with pressure.
换句话说,对温度和压强的求导顺序无关紧要,结果会表明,恒定温度下的,对应我们上面看到的,熵如何随着体积变化,这个式子告诉我们,熵如何随着压强变化。
The dA/dV is calculated at constant temperature.
就像这样,dA/dV是在恒定温度下的偏导数。
That is, it's easy to write down straight away that dG with respect to temperature at constant pressure S is minus S.
这就是说,可以很简单的写出dG在,恒定压强下对温度的偏导数,是负。
We know how the volume and temperature vary with respect to each other at constant pressure.
知道在恒定压强下,体积如何随着温度变化。
You know how pressure changes with temperature at constant volume if you know the equation of state.
如果你知道状态方程,知道在体积恒定的时压强如何随着温度变化。
The purpose here is to look at a series of processes in which temperature is held constant, and we're going to calculate how much work we get from allowing a gas to expand under various conditions.
目的是让大家了解一下,几个保持温度不变的过程,然后我们将计算,气体在不同膨胀过程中,的对外做功。
pV Also A plus pV and G is minimized at equilibrium with constant temperature and pressure.
同时等于亥姆赫兹自由能A加上,同时在恒定的温度和压强下。
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