Using Gibbs Free Energy Bozeman Science English Chinese (Simplified)

Using Gibbs Free EnergyYouTube↗ IA↗(long shot)
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Hi. It's Mr. Andersen and this is chemistry essentials video 59. It's on using Gibbs Free

你好。这是安德森老师，这是化学视频59。我们今天要学习的是怎样使用吉布斯自由

Energy which is essentially energy that's available to do work. So if I were to push

能，也就是可以做功的能量。我现在要推一下

this sphere right here, it's going to move down and it's going to move back. Where's

这个球体，它会向下移动，然后会移动回来。这个能量

the energy coming from? Well that would be gravitational potential energy being converted

来自何处呢？这将是重力势能转化

to kinetic energy. Eventually it comes to rest at the bottom. But if we think of this

为动能。如果我们继续让它这样移动，它最后会留在底部。但是，如果我们把这当作

as an analogy it really explains what's going on in a chemical or physical process. What

一个比喻，它可以说明在化学或物理变化中发生着什么。

we have is reactants and we have products. Those reactants are moving towards products,

我们有的是反应物和产物。这些反应物正在逐渐变为产物，

spontaneously some are moving back. And eventually it reaches equilibrium. What's happened to

但有一些产物将会自发的变回反应物，并最终达到化学平衡。我们的

our Gibbs Free Energy? It's gone to zero. And so we look at Gibbs Free Energy, it's

吉布斯自由能怎么样了呢？它变为了零。所以如果我们关注一下吉布斯自由能，它是

a really good indicator of if we have a spontaneous reaction or a non spontaneous reaction. So

判断一个反应是否为自发反应很好的指标。所以

if Gibbs Free Energy is ever negative or less than 0, then we know that we have a spontaneous

如果吉布斯自由能如果是一个负数或小于0，那么我们就知道，这是一个自发的

reaction. We have a scenario that looks like that. Where we have energy and that energy

反应。我们有这样的一个场景。在这里，我们有一些能量，并且这些能量

can be released. If we have a delta G greater than 0 then we have a scenarios that looks

可以被释放。如果德尔塔G大于0，那么我们的场景，会是

something like this. We have an uphill reaction. It's not going to occur spontaneously. In

这样的。我们有一个上坡的反应，它不是自发的。

other words we're going to have to put a little bit of energy in for it to work. And then

换句话说，我们必须给它一点能量让他做功。然后，

finally we can have equilibrium in the middle. Now in the last video we learned that the

我们可以在中间处达到平衡。在上一段视频中我们了解到，

two things that really contribute to Gibbs Free Energy is enthalpy and entropy. In other

有两样东西可以作为吉布斯自由能，焓和熵。

words those two things together can help us determine if it's a spontaneous reaction or

也就是说这两样东西放在一起可以帮助我们判断它是否是一个自发的反应。

a non spontaneous reaction. But it doesn't answer every question. In this video I'm going

不过，这并不能回答所有问题。在这段视频中，

to try to answer every question. What's missing is our temperature. In other words T is going

我们将尝试回答每一个问题。现在我们缺少的是温度。换句话说，T

to be incredibly important. And so if we're trying to figure out if it's a spontaneous

将会是非常重要的。所以，如果我们试图决定一个反应是否是自发的，

process or not, one of the biggest things is enthalpy or the amount of internal energy.

最重要的事情之一是焓或内部能量。

And so if we have a delta H that's negative, that's a good indication that we're going

所以，如果我们的焓变，德尔塔H是负的，这可以很好地表明我们的反应是

to have a spontaneous reaction. So in a thermite reaction our reactants have more energy than

自发的。因此，在铝热反应中，反应物比产物具有

our products. It's a downhill reaction. And so we'd expect this to occur spontaneously.

更多的能量。这是一个下坡的反应。因此，我们推测这个反应是自发的。

Likewise if we were to rust iron, same thing, we're going to have more energy before then

同样地，如果我们要让铁生锈，同样的道理，我们在反应之前会比在反应之后

we do after. And energy is going to be released. That energy is going to be released into the

有更多的能量。这些能量将被释放到

surroundings. But sometimes you'll have exceptions to that rule. So like a cold pack, if you

环境中。但这个规则并不总是成立。比如说这个冰袋，如果我们考虑一下，

think about that it occurs spontaneously but in fact it's actually consuming energy. And

它的融化是自发的，但同时它在消耗能量，并且

so we're going to have a delta H that's going to be a positive value. And so we can't just

我们的焓变德尔塔H将是正值。因此，我们不能只考虑

stick with enthalpy by itself. We have to add entropy to that. So if I had these two

焓变。我们必须同时考虑熵变。所以，如果我有这两个

spheres and I had gas on the left side and I just open it up, we're going to see that

球，我在左侧充入一些气体，我如果打开这个阀门，左侧的气体

gas move from left to the right. So we're going to have this irreversible process. And

将会向右侧移动。所以，我们将有这样一个不可逆的变化。

so what's going on there, we're not changing the energy. What's really going on is entropy.

所以这里发生了什么呢？我们不能改变任何能量。真正改变的是熵。

And so these two things together, enthalpy and entropy are very important in helping

两个东西放在一起，焓和熵是帮助我们决定

up figure if this is a spontaneous process or not. So we could put it on a grid like

一个反应是否自发的重要指标。因此，我们可以把它放在这样一个

this. And so if we ever have a decrease in enthalpy, so that's going to be an exothermic

方格中。所以，如果我们的焓在减少，这将是一个放热

reaction, or one that increases entropy, we know immediately that's going to be a spontaneous

反应，若熵同时增加，我们马上知道，这将是一个自发的

reaction. Likewise if we have the opposite of that, if we have an increase in enthalpy

反应。同样，如果我们一个相反的情况，我们的焓在增加，

and a decrease in entropy we know that's going to be non spontaneous. Now the nice thing

并且熵在减少，我们知道这将是不自发的反应。但是

about that is the reverse of that we can automatically figure out is going to be spontaneous. But

它的逆反应是自发的。但

what's going to be in these other two spots. What's going to happen, for example, when

但在其他这两处将会发生什么呢？举例来说，我们有一个

we have an endothermic process but we're actually increasing entropy. Or vice versa? And so

吸热反应，但我们的熵在增加。或者反过来呢？一个很好的例子就是

a good place to look at that is just the movement of ice to water. So if we're looking at ice

冰融化成水。如果我们关注一下冰

and water, if we look at the molecules of ice there's going to be a huge amount of order

和水，冰的分子是很有秩序的。

there. And a lot of that has to do with these hydrogen bonds. If we look in liquid water

很多是因为这些氢键。如果我们再看一下在液态水

it's going to be moving around. And so if we were to move from ice to water what's that

它是可以流动的。因此，当我们将冰融为水，那是什么

process? That's simply melting. That's going to be an increase delta H. What does that

样的变化呢？这是简单的融化，并且将是增焓变化。这代表

mean? That's going to be an endothermic process. It's taking energy from its surroundings.

什么呢？这将是一个吸热过程。它是从周围环境中境获取能量。

So we're going to have a delta H that's positive. What's happening to our entropy? Our entropy

因此，我们将有一个三角形^ h这是积极的。熵发生了什么呢？我们的熵

is increasing. In other words our matter is becoming more dispersed. So where would that

正在增加。换句话说我们的物质正变得越来越混乱。那么，在这张图中，

be over here? We have an increase in enthalpy and we have also an increase in entropy. And

这种情况在哪里呢？我们的焓在增加，同时我们的熵也在增加。

so let's go in the opposite. Let's say that we're actually freezing that water. What's

让我们看一下逆反应。比方说，我们要将水凝固成冰。

going on there? We have an exothermic reaction. So we have a decrease in enthalpy and we also

这里发生着什么呢？这是一个放热反应。因此，焓在减少，

have a decrease in entropy. And so this is going to this block right here. And so in

熵也同时在减少。所以在这张图中，这代表的是这一区域。

other words if we could figure out this one slide it would help us unlock what's in these

换句话说，如果我们能明白这个幻灯，我们就能明白这两块放个

other two grids right here. And so what do you know? Well you know that if we take ice

发生着什么。我们现在知道什么？我们知道，如果我们取一块冰

and we have it in an area where our temperature is greater than 0 degrees celsius, this is

然后把它放在大于0摄氏度的地方，这将是

going to be a spontaneous reaction. In other words if you ever take ice and put it in an

一个自发反应。换句话说，只要你将冰放在

area where it's warmer than 0 degrees celsius, we know that ice is spontaneously going to

一个温度超过摄氏0度的地方，我们知道，冰将自发地

melt. Likewise if we take that water and put it in an area where it's less than 0 degrees

融化。同样，如果拿一些水，并把它放在一个小于0度

celsius, then it's going to freeze. And we also know that if it's exactly at 0 we're

的地方，它就会冻结。而我们也知道，如果它正好在0摄氏度我们

not going to see any change. It's going to be non spontaneous in either direction. So

不会观察到任何变化。这个变化将是在任一方向都是非自发的。所以

we've really answered this question right here. So if we were to look at melting, if

我们已经回答了这个问题。因此，如果我们再来看看融化，

we ever have an increase in enthalpy, so this is an endothermic reaction and an increase

这是一个增焓变化，所以这是一个吸热反应，同时是一个

in entropy, that will be spontaneous as long as we have a high enough temperature. Likewise

增熵变化，这在高温的情况下将是自发的。同样，

if we have a decrease in enthalpy, so it's an exothermic reaction and a decrease in entropy,

如果焓在下降，这是一个放热反应，若熵减少，

then that's going to be spontaneous but only at low temperatures. And so now we can finally

反应则只有在低温时是自发的。所以现在我们终于可以

come to Gibbs Free Energy, that equation. And hopefully it makes sense at this point.

考虑吉布斯自由能。我们现在应该可以理解这个公式了。

So if we were to look at Josiah Willard Gibbs' equation, this is going to be delta G on the

因此，如果我们来看看约西亚·威拉德吉布斯的公式，德尔塔G

left side. Remember if it's ever less than 0 we know this is a spontaneous reaction or

将在等号左边。请记住，如果这个量小于0，这将是一个自发的反应；

process. If it's ever greater than 0 we know that it's non spontaneous. And so it totally

如果它大于0，我们知道这是非自发反应。这样，这个方程

makes sense, this grid right here. If you have a decrease in this number, that's a negative

就很清楚了。如果你有这个量在降低，这是一个负

value. And if you have an increase in entropy, so our delta S is going up, since we're subtracting

值。如果熵在增加，我们的德尔塔S为正，当我们减去

it, that's going to give us a negative value. Likewise if we go down to this non spontaneous

它，我们会得到一个负值。同样，如果我们去到这个非自发

right here, what do we have? We have a delta H which is going to be a positive value. That's

反应，我们的增量H的将是一个正数。这将会使德尔塔G

going to make this value go up. And then our delta S, since it's negative, we're subtracting

上升。然后我们的增量S为负，当我们减去

the negatives, so that's going to be a positive. And so hopefully these two make sense. But

它，他也是一个正值。但愿你能理解这两种情况。但

now this should unlock this grid right up here. So what happens if we increase our enthalpy?

现在，我们再来看看这两格。如果我们增加焓，将会发生什么呢？

Well if we're increasing our enthalpy you would start to think well this is going to

如果我们要增加我们的焓，这个值

increase our delta G. But if we have a high temperature that's going to make our entropy

将提高我们的增量G。但是，如果我们有一个高温的环境，那我们的熵

more important since we're subtracting that value. And so we can get away with a low enthalpy

将是更重要的，因为我们减去此值。因此，即使我们有一个很小的焓

or positive enthalpy if we have a really high temperature and an increase in entropy. Likewise

或正焓，只要我们有一个非常高的温度和熵增，反应就可以进行。同样，

the same thing down here. In this case if we can have a decrease in this enthalpy, but

在这种情况下，如果我们可以的焓在减少，但是

our entropy even though it is going down, we have a really low temperature, it's not

我们的熵，即使它正在下降，如果我们有一个非常低的温度，它

going to swing as much. Now this also unlocks that whole idea of a cold pack. What's going

不会有很大的变化。现在，我们可以解释冰袋融化了。这是怎么回事

on there? Well we have an endothermic reaction. Again it's taking energy from its surroundings.

呢？井我们有一个吸热变化，它是从周围环境获取能量。

Our delta H is a positive value. And so why are we getting a spontaneous reaction, since

我们的焓增量是一个正值。为什么我们有一个自发的反应呢？

we have a delta H that's going to be a positive value? Well, we're moving from ammonium nitrate

好了，我们使硝酸铵变化为

into ions of ammonium and ions of nitrate. And since we're doing that we're increasing

铵离子和硝酸根离子。进行这个过程时，我们的熵在增加

our entropy. And so since our delta H value is going to be so big, then we're going to

即使我们的焓增如此之大，我们还是

have a spontaneous reaction. We're going to have an overall delta G that's going to be

有一个自发反应。吉布斯自由能的变量将为负。

a negative value. And so again, Gibbs Free Energy and that equation is really powerful

吉布斯自由能的公式很有用，

because it tells us exactly what's going to happen in that process. If it's less than

因为它可以告诉我们在一个反应过程中究竟会发生什么。如果它小于

0 it's going to be spontaneous. If it's greater than 0 it's going to be non spontaneous. If

0，反应是自发的。如果是大于0这将是不自发的。如果

it's equal to 0 we're at equilibrium. And I hope that was helpful.

它等于0，我们正处于平衡状态。我希望这个视频是很有帮助的。