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Description:

Anyone know what the value of "q" is? We took it into a pawn shop, but the woman just looked at us funny.

Language:
English Language

Transcript

00:04

Here’s your Shmoop du jour, brought to you by Thanksgiving Dinner, bringing atoms together [A thanksgiving dinner on a table and atoms drinking wine]

00:09

since 13.82 billion BC!

00:12

…Or maybe that was intermolecular forces….

00:15

Here’s our question…

00:17

Which of the following correctly represents the order of intermolecular forces of attraction

00:21

(IMFs) from weakest to strongest?

00:25

And here are our potential answers…

00:32

To answer this question, we first have to understand how each of these intermolecular [Hydrogen bond, dipole dipole and london dispersion having dinner]

00:36

forces of attraction work.

00:38

That might mean watching a few atom-based romcoms… you know, like Chargeless in Seattle,

00:45

or When Harry Met Electron… [Man with atom as a face meets girl with electron as a face]

00:47

Or it might just mean watching the rest of this video.

00:50

The forces listed in the question are dipole-dipole forces, London Dispersion forces, and hydrogen

00:56

bonding.

00:57

And since we don't have our copy of Bridget Jones Dipole Diary on us, let's just go through [Man in videostore picking a DVD]

01:02

them one by one…

01:03

Starting with dipole-dipole forces.

01:04

When we’re talking about dipoles, we’re actually talking about two important areas

01:08

of small electric charge on a molecule. [Electric charges]

01:11

When a bond exists in a molecule between two atoms with very different electronegativities,

01:14

the atom with the higher electronegativity hogs a disproportionate amount of electrons. [Atom grabs electronegativity at a table]

01:20

Kind of like your cat’s idea of “sharing” furniture space.

01:25

Atoms that control more electrons in a bond become more negative in charge.

01:29

This leaves the other atom in the bond with a slight positive charge.

01:32

Dipole-dipole interactions occur when the slight negative charge of an atom in a dipole [negative charges of a molecule circled]

01:36

is attracted to the slight positive charge of an atom in a dipole in a different molecule.

01:41

Which means dipole-dipole interactions attract the two molecules together. [Molecules attract to dipole dipole magnet]

01:45

Dipole-dipole interactions are reasonably strong intermolecular forces, but the strength

01:50

varies depending on the intensity of the dipole. [Dipoles with flexed biceps]

01:52

The bigger the difference in electronegativities, the stronger the interaction.

01:57

Guess what has a really low electronegativity?

01:59

Hydrogen. [Arrow points to hydrogen]

02:00

And guess what has a really high electronegativity?

02:03

…Well, lots of things, but most commonly Oxygen, Nitrogen, and Fluorine.

02:08

And because we're generous 'round these parts, we'll give you three guesses as to what a [Man holding a sign saying 3 guesses]

02:12

dipole-dipole interaction in a molecule with a bond between Oxygen, Nitrogen, or Fluorine,

02:16

and a Hydrogen is called…

02:18

Yup the answer to our super tricky question is hydrogen bonding. [Hydrogen atoms bonding and explosion occurs]

02:22

A hydrogen bond is a particularly strong dipole-dipole interaction, because the difference in electronegativity

02:28

is so large between Hydrogen and elements like Oxygen or Nitrogen.

02:32

This means that in general, hydrogen bonds will be stronger than general dipole-dipole

02:36

interactions; however, the two interactions are similar in strength. [Hands touch each other]

02:41

Since hydrogen bonds and dipole-dipole interactions are similar in strength, London dispersion [Hydrogen bonds and dipole dipole on a see-saw]

02:46

forces must be either stronger than both or weaker than both.

02:51

So where do they fall?

02:52

Well, London dispersion forces are actually a pretty weak force, because they result from

02:57

a property of the electron cloud of a molecule known as its polarizability. [Electron cloud and weather reporter man appears]

03:01

That's just a fancy way of saying that the electrons can move around to make little tiny

03:07

dipoles….giggity…. [electrons create a dipole in an electron cloud]

03:10

This happens if more electrons end up on one side of a molecule for a short period of time.

03:14

A good way to compare these forces comes, like many good things, from the kitchen. [Selection of food in a kitchen]

03:19

London Dispersion Forces are best approximated by the forces holding together wet spaghetti

03:23

noodles, whereas hydrogen bonds are like the forces holding together a single block of [Man holding large blocks of ice]

03:27

ice.

03:28

You can pull the spaghetti apart with your hands but good luck trying that with ice.

03:33

Since London Dispersion Forces are so weak, the answer must be C.

03:37

But just because London Dispersion Forces are weak, doesn't mean they can't find love. [London Dispersion Force working out in a gym]

03:42

Four Weddings and a London Dispersion Funeral….Coming soon, to a theatre near you.

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