Dipole Forces Bozeman Science English Chinese (Simplified)

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Hi. It's Mr. Andersen and this is chemistry essentials video 17. It's on

你好。这是安德森先生，这是化学基础视频17. 这是关于

dipole forces. Before we talk about dipole forces we should probably identify what a

偶极作用力。在我们谈论偶极作用力之前，我们也许应该确定什么

dipole is. Water is a great example of one. We have one oxygen and two hydrogens. And

是偶极子。水是一个很好的例子。我们有一个氧和两个氢。

since oxygen is highly electronegative, it's going to pull the electrons towards it. And

由于氧的电负性高，它将吸引电子。

so it's going to have partial positive charges where the hydrogen is. And partial negative

所以氢处将会偏正，

charges where the oxygen is. And so it's a dipole. What does that mean? It's if we ever

氧处将会偏负。因此，这是一个偶极子。这意味着什么？这是如果我们

have separation between the positive and negative charges we've created a dipole from the positive

有正电荷和负电荷之间的分离, 我们就创建了一个从正到负的偶极子。

to the negative. And so dipole forces are going to usually occur when we have at least

所以偶极作用力通常出现在至少有

one polar molecule. And so that's called a dipole. It's going to have partial charges,

一种极性分子时。所以，这就是所谓的偶极子。它会有部分电荷，

positive and negative. And so we can have a dipole force between a dipole and a dipole.

正和负。因此，我们可以有一个偶极和偶极之间的偶极作用力。

So it's called a dipole-dipole force. We can use diagrams to figure out how they're going

因此，它被称为偶极-偶极作用力。我们可以用示意图来弄清楚他们是如何取向的。

to orient themselves. And the most famous one is called hydrogen bonds. Hydrogen bonds

而氢键是最有名的(偶极作用力)例子之一。

are going to form when we have hydrogen bonded to either oxygen, nitrogen or fluorine. And

当氧，氮或氟结合氢时, 就会形成氢键。

it creates a dipole. It's going to hold molecules together. We could also have an attraction

形成的偶极子将分子聚在一起。

between a dipole and an induced dipole. This is something that's not polar but can be for

我们也可以有偶极和诱导偶极子之间的吸引力。这种虽然不带极性，但有瞬间极性。

just a second. The strength of this force between the two is going to be based on the

这两者之间的力的强度将是基于极化度，

polarizability, in other words how much we can make that turn into a dipole. And then

换句话说, 我们可以将多少转化成偶极子。

the magnitude of the original dipole. And then finally we can have a force between a

进而原始偶极子的大小。然后终于可以有一个偶极子和离子之间的作用力。

dipole and an ion. This is going to be really important when we're using dipoles to breakdown

我们使用偶极子溶解溶质时, 这非常重要。

solutions. An example would be water breaking down salt. And so before we get into dipoles,

例如:水溶解(食)盐。所以，在我们讲到偶极子之前，

make sure you understand the difference between intermolecular and intramolecular. Intermolecular

首先搞清楚分子间以及分子内作用力的区别,

is going to be between molecules. Like interstate goes between states. And so the force between

分子间作用力将是分子之间。就像州间是指州与州之间。

this one molecule of hydrochloric acid and this one is going to be intermolecular. Intramolecular

因此，这个盐酸分子与另一个盐酸分子的（关系）是分子间的。

is going to be the covalent bond between the chlorine and the hydrogen. Likewise we could

分子内(作用力)是指氯与氢之间的共价键。同样，我们可以

have water around salt. They're going to have a ionic bond between the chlorine and the

有水绕盐。水分子与氯离子, 水分子与钠离子之间将形成离子键。

sodium ions. But it would be an intermolecular between the water and the ions themselves.

但它是将水和离子之间的分子间(作用力)。

Also this helps explain the difference between real and ideal gases. Remember ideal gases

也这有助于解释真实和理想气体之间的差异。记得理想气体

are just theoretical. But as the gases become closer to liquid, as they start to condense,

只是理论上的。但是，随着气体变得更接近于液体，当它们开始凝结时，

we're going to start to have attractive forces and some of these are going to be dipole-dipole

开始会有吸引作用，其中部分会是偶极－偶极作用力。

forces. So let's look at a specific dipole. Let's say we have hydrochloric acid. Hydrochloric

让我们来看一个具体的偶极子。比方说，盐酸。

acid is going to have one atom of hydrogen and one of chlorine. Chlorine is going to

盐酸有一个氢原子和一个氯原子。

pull that electron towards itself. And so it's going to have a partial positive and

氯要朝自身方向拉动电子。便会出现部分正电荷以及部分负电荷。

negative charge. Positive is going to be where the hydrogen is. Negative is going to be where

正电荷在氢处, 负电荷在氯处.

the chlorine is. And so if we have two of these, what we'll get is a dipole-dipole force.

两个盐酸分子便构成偶极-偶极作用力。

It's simply a force between the two dipoles. And it's going to hold hydrochloric acid together.

这只是两个偶极子之间的作用力, 它会将盐酸分子维持在一起。

So if I had a bunch of hydrochloric acid molecules and I put them like this. They can never exist

所以，如果我有一堆盐酸分子的我把它们摆成这样。它们永远不会这样存在。

like this. But let's say I put them like that. With all of their negatives on the inside

但是，如果把它们摆成这样，所有负电荷在内部，所有正电荷在外面。

and positives on the outside, how do you think they would orient themselves? Well, it would

你猜它们会怎样取向呢？那么，它会

be something like this. They're going to orient themselves so we have a negative to a positive

是这样的。他们将定位成这样,由负到正

to a negative to a positive to a negative to a positive. So imagine in hydrochloric

到负到正到负到正。可想而知, 盐酸分子

acid we have all these interconnections going on. Now a specific type of dipole-dipole is

都是以这种内部连接方式存在的。氢键是偶极－偶极作用力的一个特例。

going to be a hydrogen bond. Hydrogen bonds are going to occur, lots of people think it's

氢键将要发生，很多人认为，氢键是由氢与其他(元素)之间形成的。

between hydrogen and something else. It's not that. So hydrogen bond is going to occur

when we have hydrogen bonded to either a nitrogen, oxygen or a fluorine. And so in water we have

当有氢键合到任何一个氮，氧或氟时, 就会生成氢键。

hydrogen bonded to oxygen. So when it does that, we're going to have unequal sharing

因此在水中，有氢与氧结合。因此，当它结合时，就会有不均等的共用(電子),

and so we're going to have a dipole. We're going to have a negative side where the oxygen

就会产生偶极子。就会有带负电的氧，

is. And a positive side where the hydrogen is. Now let me show you where the hydrogen

以及带正电的氢。我现在告诉你氢键在哪。

bond is. This is how water would really orient itself. This is going to be a hydrogen bond

这就是水很会定位自己。就在这里生成氢键,

right here, between the hydrogen and the oxygen of an adjacent molecule. Or between this hydrogen

在氢和相邻分子中的氧之间。或者是在这个氢

and this oxygen of this adjacent molecule. And hydrogen bonds are incredibly important.

与其相邻的氧之间。氢键是非常重要的。

And they allow small molecules like water to have pretty good bonds that hold them together.

氢键使象水一样的小分子（之间）有很强的键保持在一起。

In fact that's why it's really hard to change the temperature of water. It has a high specific

事实上，这就是为什么它真的很难改变水的温度。它具有高的比热。

heat. It's due to these hydrogen bonds. But we could find it in larger molecules as well.

正是由于这些氢键。我们也可以在大分子中找到氢键。

So if we're looking at the nitrogenous bases, these are the bases on the inside of DNA,

所以如果我们来看一下的DNA内侧的含氮碱基，

this ladder. What's holding them together are going to be these hydrogen bonds. Hydrogen

这个(扭曲的的分子)梯(双螺旋结构)。是氢键将它们聚在一起。

bonds are holding it. It's between the hydrogen and oxygen. Or hydrogen and nitrogen of another

氢键在维持这个(分子梯结构)。氢键在氢与其他分子的氧之间，或是在氢与其他分子的氮之间。

molecule. And so hydrogen bonds are incredibly important. But again they're dipole-dipole.

所以, 氢键是非常重要的。但是再次（强调），氢键是偶极－偶极作用。

We could also have a dipole induced dipole force. Okay. What's this going to be? It's

我们还可以有一个偶极诱导偶极作用力。那么,这又是什么(情况)呢?

going to be between a polar molecular and something that has no charge at all. What's

这是在一个极性分子与一个完全不带电的分子之间。

something that has no charge? A noble gas is an example of that. So let's say we have

什么(物质)会没有电荷呢？惰性气体是一个很好的例子。那么，如果我们有

hydrochloric acid molecule next to argon. Argon remember is going to have no charge.

盐酸分子在氩气旁边。注意氩气不带电。

All of the electrons are equally distributed. Well as it comes closer, watch what happens

所有氩上的电子都平均分配。那么当它靠近时，观察氩气分子靠近盐酸分子发生的现象。

as argon approaches hydrochloric acid. Some of those electrons in its surface are going

氩气分子靠近盐酸分子发生的现象。氩表面上的部分电荷被盐酸分子的正电荷吸引。

to be attracted towards this positive charge of the hydrogen. And as a result, what we're

其结果，会出现一个临时偶极子，

going to create is a temporary dipole, or an instantaneous dipole. So it just happens

或瞬时偶极作用。因此，它只在一小部分时间内发生。

for a fraction in time. But now we have this force holding them together. A force between

现在，我们有了使他们保持在一起的力量。

the dipole and an induced dipole. Now what's going to increase the ability to be induced?

这种偶极与诱导偶极之间的力量。什么能够增加被诱导的能力呢？

Well it's going to be the strength of this dipole. The more strength there is in that

是这个偶极子极性的强度，它的极性强度越强，越容易诱导偶极.

polarity, the more likely we are to induce dipoles. And then the other thing is going

另外就是另一个原子或分子的极化度。

to be the polarizability of that other atom or other molecule. The more electrons it has,

所带电子越多，

the more likely those electrons can be tugged on and we can make these instantaneous dipoles.

这些电子被吸引成瞬间偶极的几率就越大。

And then finally we could have an attraction between a dipole and an ion. And so a great

最后，还有一种偶极与离子之间的吸引力。

example of this is how water dissolves salt. There are going to be huge bonds, intermolecular

水是如何溶解食盐的便是一个很好的例子。氯离子与钠离子之间存在极强的分子间键。

between the chloride and the sodium ions. And that's why salt has this beautiful crystalline

的氯和钠离子之间。这就是盐有美丽结晶的原因。

structure. But you know if we add it to water we can quickly break it down. It can form

但是，你知道，盐中加水, 盐会很快溶解成溶液。

a solution. Well what's going on there? We have a chlorine ion. And then we have a sodium

那么这是怎么回事呢？我们有一个氯离子。然后还有一个钠离子。

ion. And what's going to happen is the water will orient like this around that chloride

会怎样呢，水会像这样围绕氯离子定向。

ion. And so we're going to have the positive ends of the water attracted to the negative

那么，水的正极端被氯离子的负极端吸引。

ends of the ion. If we look at the sodium we're going to have the negative parts of

对钠离子来说，水的负极端被钠离子的正极端所吸引。

the water attracted to the positive parts of the sodium. And so what they're really

doing is kind of ushering these ions away from that original ionic compound. What happens

水像像是从原来的化合物中”请走“这些离子。

if we remove the water? Then those ionic compounds come back again and we get that sodium chloride.

如果去掉水会怎样呢? 那么, 这些离子化合物重新变回氯化钠。

So did you learn the following? That we could relate the real gas behavior to some of these

所以，你学过这些吗? 涉及真实气体与分子间作用力。

intermolecular? Remember as a gas gets closer to condensation we're going to have more of

记得气体越凝集分子间吸引力越大。

these attractive intermolecular forces. Did you learn to relate the feature of a polar

你学过极性分子的特性与分子间吸引力有关吗？

molecule to the attraction between them. Or remember this diagram shows that. We've got

记得这个图显示了这一点。有两个偶极子，

two dipoles. And you could probably turn it so you could orient it the correct way. And

可以转动到正确定向。

then finally could we use Coulomb's law to explain why dipoles are attracted to ions?

那么，最终可以用库仑定律来解释为什么离子吸引偶极子。

Remember all it has to do is those partial charges of the dipole, in this case water,

记得这与偶极子的部分电荷有关, 在这种情况下的水，

attracted to the ionic charges or the ions. And so that's going to allow it to dissolve

被离子电荷或离子所吸引。就会发生水溶解。

it. And it's simply Coulomb's law. That attracting between positive and negative. And I hope

只是库仑定律。正极负极之间的吸引力。

that was helpful.

我希望这是有益的.

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