Rebellion

WEBVTT
Kind: captions
Language: en

00:00:00.510 --> 00:00:03.000
- [Presenter] Sound the
drums of war, wordsmiths,

00:00:03.000 --> 00:00:06.570
because today I teach you about rebellion.

00:00:06.570 --> 00:00:08.163
Man, I'm a great influence.

00:00:09.060 --> 00:00:10.890
Rebellion.

00:00:10.890 --> 00:00:11.723
It's a noun.

00:00:11.723 --> 00:00:14.940
It means war or pushback
against a government

00:00:14.940 --> 00:00:16.440
or an authority, right?

00:00:16.440 --> 00:00:18.270
The American Revolutionary War

00:00:18.270 --> 00:00:21.090
began as a rebellion
against the British Crown.

00:00:21.090 --> 00:00:23.310
Now, this word has Latin origins.

00:00:23.310 --> 00:00:27.210
The root bel comes from the
Latin bellum, meaning war,

00:00:27.210 --> 00:00:30.960
and the prefix re means
again, against, or back.

00:00:30.960 --> 00:00:32.310
So rebels stand up

00:00:32.310 --> 00:00:35.340
and maybe go to war
against something, right?

00:00:35.340 --> 00:00:36.810
They're seeking change.

00:00:36.810 --> 00:00:39.180
So two countries going
to war with each other

00:00:39.180 --> 00:00:40.230
is not a rebellion,

00:00:40.230 --> 00:00:42.450
but in uprising within a country,

00:00:42.450 --> 00:00:46.020
protesting a tyrannical
ruler, that's a rebellion.

00:00:46.020 --> 00:00:47.760
So re and bel,

00:00:47.760 --> 00:00:50.610
those are our word parts
I wanna focus on today.

00:00:50.610 --> 00:00:53.070
I'm gonna put on some
music for about 10 seconds,

00:00:53.070 --> 00:00:56.370
and while I do that, come up
with as many words as you can

00:00:56.370 --> 00:00:59.280
that contain those elements.

00:00:59.280 --> 00:01:01.297
Okay Let's go.

00:01:01.297 --> 00:01:03.880
(upbeat music)

00:01:12.840 --> 00:01:16.230
Okay, here are three that
I came up with. Remake.

00:01:16.230 --> 00:01:17.520
Like there's an old movie

00:01:17.520 --> 00:01:19.560
and you're making a new
version of it, right?

00:01:19.560 --> 00:01:22.410
You're making it again. Remake.

00:01:22.410 --> 00:01:23.280
Belligerent.

00:01:23.280 --> 00:01:27.600
One of my favorite adjectives.
It means hostile or warlike.

00:01:27.600 --> 00:01:30.240
A belligerent person
starts a lot of arguments,

00:01:30.240 --> 00:01:31.620
a lot of fights.

00:01:31.620 --> 00:01:33.270
And this last one, rebel, right?

00:01:33.270 --> 00:01:34.830
Also contained within rebellion.

00:01:34.830 --> 00:01:37.200
This word can be a noun or a verb.

00:01:37.200 --> 00:01:38.310
I wanted to flag it

00:01:38.310 --> 00:01:40.290
because pronunciations are different

00:01:40.290 --> 00:01:41.880
depending on how you use it.

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When it's a person, they're a rebel.

00:01:43.650 --> 00:01:47.910
But the thing that a rebel
does is rebel, fights back.

00:01:47.910 --> 00:01:51.483
The emphasis changes from the
first syllable to the second.

00:01:53.010 --> 00:01:55.200
First syllable. Second syllable.

00:01:55.200 --> 00:01:56.760
The nouns verbed.

00:01:56.760 --> 00:02:00.330
The rebels rebelled in their rebellion.

00:02:00.330 --> 00:02:02.490
Let's use rebellion in a sentence or two.

00:02:02.490 --> 00:02:04.080
To the mind of a dictator,

00:02:04.080 --> 00:02:06.840
something as innocent as
a sidewalk chalk drawing

00:02:06.840 --> 00:02:09.450
could be seen as an act of rebellion.

00:02:09.450 --> 00:02:12.030
So it's seen as an act of war

00:02:12.030 --> 00:02:14.790
or of open resistance to the dictator.

00:02:14.790 --> 00:02:15.780
Look at a mouth open.

00:02:15.780 --> 00:02:17.970
He looks so scandalized by little house.

00:02:17.970 --> 00:02:21.780
Marta rebelled quietly. She
pulled doors marked push.

00:02:21.780 --> 00:02:23.730
She rode her bike through
the drive-through.

00:02:23.730 --> 00:02:26.010
She microwaved fish in the office.

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I feel like I'm contributing

00:02:27.030 --> 00:02:30.510
to kind of an anti-fish narrative
here, and that's unfair.

00:02:30.510 --> 00:02:33.840
I microwave fish in the Khan
Academy lunchroom, whatever.

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I'm not too proud to admit it.

00:02:35.580 --> 00:02:37.350
Does that make me a hero?

00:02:37.350 --> 00:02:38.820
Maybe.

00:02:38.820 --> 00:02:41.403
Does it make me a rebel? Oh, you betcha.

00:02:42.480 --> 00:02:45.030
Now, if you excuse me,
your boy's got a serving

00:02:45.030 --> 00:02:46.710
of tuna casserole in the refrigerator,

00:02:46.710 --> 00:02:49.861
and I can't eat it cold,
if you know what I mean.

00:02:49.861 --> 00:02:53.257
So you can learn anything. Dig it out.

00:02:54.892 --> 00:02:58.464
(microwave door opens)

00:02:58.464 --> 00:03:00.916
(microwave beeps)

00:03:00.916 --> 00:03:04.780
(microwave door opens)
(presenter laughs)


Eliminate

WEBVTT
Kind: captions
Language: en

00:00:00.210 --> 00:00:01.650
- [David] What's up, wordsmiths?

00:00:01.650 --> 00:00:04.971
This video is about the word eliminate.

00:00:04.971 --> 00:00:06.963
Eliminate.

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It's a verb.

00:00:08.633 --> 00:00:11.313
It means to remove or
get rid of something.

00:00:12.150 --> 00:00:14.580
The word comes to us from Latin,

00:00:14.580 --> 00:00:17.550
and it's a combination of two parts, ex,

00:00:17.550 --> 00:00:20.550
which means out or away, think exit,

00:00:20.550 --> 00:00:25.550
and limin, which means edge
or threshold, think limit.

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You're pushing something
over the threshold

00:00:27.960 --> 00:00:29.159
and out the door.

00:00:29.159 --> 00:00:29.992
(instructor mimicking door slamming)

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There he goes.

00:00:30.825 --> 00:00:32.493
You'll notice it's not exliminate.

00:00:33.390 --> 00:00:36.813
Sometimes ex gets
shortened down to just e,

00:00:37.860 --> 00:00:41.400
as it does here or in
words like eject or emit.

00:00:41.400 --> 00:00:45.270
For now, just know that
sometimes, ex becomes e,

00:00:45.270 --> 00:00:46.770
as in eliminate.

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Thinking of those elements,

00:00:48.420 --> 00:00:52.650
ex or lim, try to come up
with a couple of similar words

00:00:52.650 --> 00:00:54.750
in English that contain those parts.

00:00:54.750 --> 00:00:57.180
I'll give you 10 seconds, all right?

00:00:57.180 --> 00:00:59.152
Take it away, music break.

00:00:59.152 --> 00:01:01.652
(light music)

00:01:10.050 --> 00:01:11.253
Here are some of mine:

00:01:12.150 --> 00:01:14.460
exit, like the opposite of an entrance,

00:01:14.460 --> 00:01:16.260
a place you go out of,

00:01:16.260 --> 00:01:19.710
limit, like the edge or
the end of something,

00:01:19.710 --> 00:01:21.810
and subliminal, this is a fun one.

00:01:21.810 --> 00:01:24.870
It means below the threshold of awareness.

00:01:24.870 --> 00:01:27.450
You might have heard of
subliminal messaging,

00:01:27.450 --> 00:01:29.700
like how I've been
subtly flashing the words

00:01:29.700 --> 00:01:33.420
eat more mangoes onscreen
for the last five seconds.

00:01:33.420 --> 00:01:36.270
I haven't been paid by any
mango growers or anything.

00:01:36.270 --> 00:01:37.950
I just think they're tasty fruits.

00:01:37.950 --> 00:01:41.550
But to eliminate something
is to get rid of it.

00:01:41.550 --> 00:01:42.393
For good.

00:01:43.260 --> 00:01:44.820
Let's try it in a sentence.

00:01:44.820 --> 00:01:47.340
And you can see how it comes across.

00:01:47.340 --> 00:01:51.997
It usually has a kind of dire
connotation, kinda scary.

00:01:51.997 --> 00:01:55.020
"Our new directive of
public order will eliminate

00:01:55.020 --> 00:01:57.150
those troublemakers for good,"

00:01:57.150 --> 00:02:00.060
sneered the Minister of Peace.

00:02:00.060 --> 00:02:01.350
Right, creepy, ew.

00:02:01.350 --> 00:02:03.330
I didn't even need to do the voice.

00:02:03.330 --> 00:02:05.580
Getting rid of troublemakers for good

00:02:05.580 --> 00:02:07.560
sounds pretty frightening.

00:02:07.560 --> 00:02:08.763
Not gonna lie.

00:02:09.900 --> 00:02:11.790
A less creepy example, you might see it

00:02:11.790 --> 00:02:14.347
in an advertising context, like,

00:02:14.347 --> 00:02:18.780
"This fabulous product eliminates
99% of household odors!"

00:02:18.780 --> 00:02:21.210
Fabulous little product in its spray can.

00:02:21.210 --> 00:02:23.490
It removes the odors.

00:02:23.490 --> 00:02:24.330
It takes them away.

00:02:24.330 --> 00:02:26.280
It puts them beyond the threshold,

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the limit of your awareness.

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I hope that this video has
eliminated any confusion

00:02:31.860 --> 00:02:34.710
about the meaning of the word eliminate.

00:02:34.710 --> 00:02:37.050
All right, I'm exiting now.

00:02:37.050 --> 00:02:39.270
Catch you in the next one.

00:02:39.270 --> 00:02:41.403
You can learn anything, David out.


Defiant

WEBVTT
Kind: captions
Language: en

00:00:01.140 --> 00:00:02.730
- [David] To arms, wordsmiths!

00:00:02.730 --> 00:00:05.970
This video is about the word defiant.

00:00:05.970 --> 00:00:07.893
De-fi-ant.

00:00:08.820 --> 00:00:10.170
It's an adjective.

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This word means openly disobeying rules,

00:00:13.050 --> 00:00:15.570
pushing back against authority.

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This word comes to us from
French and ultimately Latin,

00:00:18.480 --> 00:00:22.470
a late Latin verb, disfidare, which means

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to renounce, to go back on one's faith.

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Fidus is Latin for faith or
trust and dis means not or away.

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So with that in mind, what
are some English words

00:00:32.430 --> 00:00:35.280
that you can think of that
contain those elements?

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Dis or fid?

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You're probably wondering
about dis and de,

00:00:39.180 --> 00:00:40.650
those are different sounds.

00:00:40.650 --> 00:00:42.390
They mean the exact same thing in Latin,

00:00:42.390 --> 00:00:44.430
they both mean not or away.

00:00:44.430 --> 00:00:45.960
I'll give you 10 seconds to think,

00:00:45.960 --> 00:00:48.240
and then show you what I came up with.

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Here we go.

00:00:49.201 --> 00:00:54.201
(instructor snaps fingers)
(futuristic upbeat music)

00:01:02.700 --> 00:01:03.930
Here's some of mine.

00:01:03.930 --> 00:01:05.130
Dislike, right?

00:01:05.130 --> 00:01:06.960
Not liking something.

00:01:06.960 --> 00:01:10.470
Fidelity, which is like
faithfulness or loyalty,

00:01:10.470 --> 00:01:13.950
and confidence, which is like
saying you trust yourself.

00:01:13.950 --> 00:01:15.600
You have faith in yourself.

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Let's use it in a sentence or two.

00:01:17.130 --> 00:01:19.740
In fact, let me show you a
couple of forms of this word

00:01:19.740 --> 00:01:23.430
'cause you can use it as
a verb, as defy or defies

00:01:23.430 --> 00:01:28.200
as in Luella defied her
father and snuck out at night.

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And then when we turn it
back into an adjective

00:01:30.000 --> 00:01:33.216
by adding that A-N-T ending,
we get defiant again.

00:01:33.216 --> 00:01:35.190
Plumeria Goodheart was defiant.

00:01:35.190 --> 00:01:37.830
She would never give
in to Lady Mordigaunt.

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Little hobbit-y woman over
her, brimming with goodness,

00:01:40.080 --> 00:01:42.967
big evil sorceress over here,
crackling with lightning.

00:01:42.967 --> 00:01:43.837
"Feel my wrath!"

00:01:43.837 --> 00:01:45.780
"I'll never join you,"
et cetera, et cetera.

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You get the picture.

00:01:46.680 --> 00:01:51.540
To be defiant is to be bold,
audacious, rebellious, unruly.

00:01:51.540 --> 00:01:56.540
A defiant person openly flouts
rules and fights authority.

00:01:56.880 --> 00:02:01.290
So when you wanna turn that
adjective defiant into a noun,

00:02:01.290 --> 00:02:04.230
you turn the A-N-T into A-N-C-E.

00:02:04.230 --> 00:02:06.810
Defiant becomes defiance.

00:02:06.810 --> 00:02:09.390
That's how you talk about it as a noun.

00:02:09.390 --> 00:02:10.890
Let me use it in a sentence.

00:02:10.890 --> 00:02:14.280
The rebels showed their
defiance through performances

00:02:14.280 --> 00:02:16.260
of forbidden dance.

00:02:16.260 --> 00:02:18.240
The most forbidden dance
of all is the dance

00:02:18.240 --> 00:02:20.250
of neurons blazing through your mind

00:02:20.250 --> 00:02:21.510
as they make new connections.

00:02:21.510 --> 00:02:23.640
Sparks flying in the deepness of your mind

00:02:23.640 --> 00:02:25.890
as your brain becomes a
bright shimmering beacon

00:02:25.890 --> 00:02:26.940
of knowledge.

00:02:26.940 --> 00:02:30.390
The rumba of rumination,
the bachata of brilliance,

00:02:30.390 --> 00:02:33.570
the lambada of learning.

00:02:33.570 --> 00:02:36.813
You can learn anything, David out.


Invalid

WEBVTT
Kind: captions
Language: en

00:00:00.930 --> 00:00:02.550
- [David] Hello, Wordsmiths.

00:00:02.550 --> 00:00:05.670
The word we're featuring
in this video is invalid.

00:00:05.670 --> 00:00:07.230
That's right, it's not true.

00:00:07.230 --> 00:00:10.950
Or rather, that's what it means, invalid.

00:00:10.950 --> 00:00:14.550
Incorrect, false, not accepted.

00:00:14.550 --> 00:00:16.290
It's an adjective.

00:00:16.290 --> 00:00:20.280
It comes from Latin where
the prefix in means not,

00:00:20.280 --> 00:00:23.250
and the word validus means strong.

00:00:23.250 --> 00:00:26.520
So it literally means not strong or weak.

00:00:26.520 --> 00:00:28.920
A weak argument, a weak law,

00:00:28.920 --> 00:00:30.960
someone's argument might be invalid

00:00:30.960 --> 00:00:34.050
because it was based on faulty evidence.

00:00:34.050 --> 00:00:35.730
When you look at invalid,

00:00:35.730 --> 00:00:38.430
can you recognize any other English words,

00:00:38.430 --> 00:00:41.133
anything with in or vow in it?

00:00:42.210 --> 00:00:45.120
Take 10 seconds of this
music break to come up

00:00:45.120 --> 00:00:47.070
with some possibilities.

00:00:47.070 --> 00:00:48.037
Here we go.

00:00:48.037 --> 00:00:50.620
(upbeat music)

00:00:59.460 --> 00:01:03.120
Validate, right to prove that
something's right or true.

00:01:03.120 --> 00:01:05.070
I validate your parking.

00:01:05.070 --> 00:01:07.200
I validate your feelings.

00:01:07.200 --> 00:01:09.100
Get you with the big validation stamp.

00:01:10.110 --> 00:01:13.770
Value, meaning something
that has worth, right?

00:01:13.770 --> 00:01:15.840
Strength in worth.

00:01:15.840 --> 00:01:19.350
And inability, which is when
you cannot do something.

00:01:19.350 --> 00:01:21.480
There's ability, right,
when it can do a thing.

00:01:21.480 --> 00:01:25.410
And inability, which is its opposite.

00:01:25.410 --> 00:01:29.100
Let's spend some time
talking about that in prefix,

00:01:29.100 --> 00:01:31.830
honestly, because it can get confusing.

00:01:31.830 --> 00:01:34.590
There are two different
prefixes in English,

00:01:34.590 --> 00:01:36.720
both coming from Latin that are spelled

00:01:36.720 --> 00:01:38.460
and pronounced the same way.

00:01:38.460 --> 00:01:42.690
Both in, I-N, that have
different meanings.

00:01:42.690 --> 00:01:47.310
In, or sometimes I'm, I-M, means not.

00:01:47.310 --> 00:01:50.220
Exactly like the native English, un.

00:01:50.220 --> 00:01:52.953
Like unlikeable, unlovely.

00:01:53.970 --> 00:01:58.860
Think invalid, impolite,
infrequent, right.

00:01:58.860 --> 00:02:02.070
Not correct, not polite, not frequent.

00:02:02.070 --> 00:02:06.243
And then there's in,
I-N, that means inside.

00:02:07.200 --> 00:02:09.753
This also sometimes appears as E-N, en,

00:02:11.400 --> 00:02:13.620
like insight looking inward

00:02:13.620 --> 00:02:17.040
or insert, which is to put
something into something else.

00:02:17.040 --> 00:02:21.930
Or with the E-N, you can
have it as enlist or enrich.

00:02:21.930 --> 00:02:26.220
But today in this video,
we're talking about the in

00:02:26.220 --> 00:02:28.080
that means un.

00:02:28.080 --> 00:02:30.240
The in that means not.

00:02:30.240 --> 00:02:33.330
We'll return to this topic
for sure in other videos.

00:02:33.330 --> 00:02:36.720
Now let's use invalid in a sentence.

00:02:36.720 --> 00:02:37.920
I can't log in.

00:02:37.920 --> 00:02:41.070
It says my password is invalid.

00:02:41.070 --> 00:02:42.090
Makes you furious.

00:02:42.090 --> 00:02:44.640
When something's invalid, it doesn't work.

00:02:44.640 --> 00:02:45.473
It isn't correct.

00:02:45.473 --> 00:02:48.360
When it's valid, it's
proper and appropriate.

00:02:48.360 --> 00:02:51.510
But when it's invalid,
it won't be accepted.

00:02:51.510 --> 00:02:52.890
It's no good.

00:02:52.890 --> 00:02:54.510
You know what is good though?

00:02:54.510 --> 00:02:57.090
You, you're good.

00:02:57.090 --> 00:02:59.580
I believe in you and
the vocabulary journey

00:02:59.580 --> 00:03:01.440
that we are on together.

00:03:01.440 --> 00:03:03.993
You can learn anything, David, out.


Policy

WEBVTT
Kind: captions
Language: en

00:00:01.080 --> 00:00:02.640
- [Instructor] Hello, wordsmiths.

00:00:02.640 --> 00:00:06.195
The word we're featuring
in this video is policy,

00:00:06.195 --> 00:00:10.489
which means an official
rule or set of rules.

00:00:10.489 --> 00:00:12.297
Policy.

00:00:12.297 --> 00:00:13.383
It's a noun.

00:00:14.400 --> 00:00:16.620
It comes from the Greek word polis,

00:00:16.620 --> 00:00:18.930
which means city.

00:00:18.930 --> 00:00:21.723
As a root, has to do with
cities and government.

00:00:22.650 --> 00:00:25.500
I live in Washington, DC so
when I think of this root,

00:00:25.500 --> 00:00:28.290
I think of the capitol building itself,

00:00:28.290 --> 00:00:30.600
a government building in
the middle of the city,

00:00:30.600 --> 00:00:34.490
where rules or policies are created.

00:00:34.490 --> 00:00:37.500
Can you think of words that
sound similar to policy

00:00:37.500 --> 00:00:39.543
that might have that same root, polis?

00:00:39.543 --> 00:00:43.230
Bear in mind that sometimes
we drop the S in polis

00:00:43.230 --> 00:00:44.580
when making new words.

00:00:44.580 --> 00:00:47.490
I'll give you 10 seconds to list some out.

00:00:47.490 --> 00:00:49.097
Cue the music wall.

00:00:49.097 --> 00:00:51.597
(light music)

00:01:00.248 --> 00:01:04.350
Here are three related words I thought of.

00:01:04.350 --> 00:01:07.950
Police, the people who enforce the law,

00:01:07.950 --> 00:01:11.400
politics, or how people
make decisions together

00:01:11.400 --> 00:01:16.400
in a society and metropolis, a huge city.

00:01:17.370 --> 00:01:19.920
So you can see how all of
those words are related

00:01:19.920 --> 00:01:22.230
to governments or cities.

00:01:22.230 --> 00:01:25.803
Let's use policy in a sentence
so you can get a sense of it.

00:01:26.670 --> 00:01:28.500
It's a state policy in Florida

00:01:28.500 --> 00:01:31.920
that if you encounter
a manatee in the wild,

00:01:31.920 --> 00:01:34.080
you have to give her $10.

00:01:34.080 --> 00:01:36.960
The connotation, the feeling of policy is

00:01:36.960 --> 00:01:38.370
that it's an official rule.

00:01:38.370 --> 00:01:39.810
So something that a business

00:01:39.810 --> 00:01:41.640
or a government might come up with.

00:01:41.640 --> 00:01:45.330
A restaurant might have a strict
policy against bringing in

00:01:45.330 --> 00:01:47.460
some other restaurant's food.

00:01:47.460 --> 00:01:51.270
Our policy: no outside food or drink.

00:01:51.270 --> 00:01:52.920
Oh no, this manatee went into a restaurant

00:01:52.920 --> 00:01:55.350
with food from another establishment.

00:01:55.350 --> 00:01:59.430
The D stands for Dugong, which
is another kind of sea cow.

00:01:59.430 --> 00:02:01.290
That's all the time
we've got for this one.

00:02:01.290 --> 00:02:03.390
Tip your server, support
your local manatee,

00:02:03.390 --> 00:02:05.730
and you can learn anything.

00:02:05.730 --> 00:02:06.563
David out.


Align

WEBVTT
Kind: captions
Language: en

00:00:00.090 --> 00:00:01.260
- [David] Hey, there, Wordsmiths.

00:00:01.260 --> 00:00:04.187
This video is about the word align, align.

00:00:05.460 --> 00:00:06.900
This word has two definitions.

00:00:06.900 --> 00:00:11.900
The first is to support, ally
or associate with someone.

00:00:11.910 --> 00:00:13.140
And the second definition

00:00:13.140 --> 00:00:14.820
is to put things in a straight line.

00:00:14.820 --> 00:00:17.010
That's its literal definition.

00:00:17.010 --> 00:00:20.010
It comes from the Latin
lin, which means line.

00:00:20.010 --> 00:00:23.640
It's a very useful little
word and it is a verb.

00:00:23.640 --> 00:00:26.310
Now, I'm gonna throw y'all
a ten second music break

00:00:26.310 --> 00:00:27.510
and in that time,

00:00:27.510 --> 00:00:31.525
see how many words you can
come up with that use lin.

00:00:31.525 --> 00:00:34.191
Please, Mr. Music, won't you play?

00:00:34.191 --> 00:00:37.358
(bright upbeat music)

00:00:45.000 --> 00:00:46.890
Here are some words I
came up with earlier,

00:00:46.890 --> 00:00:48.240
cooking show style.

00:00:48.240 --> 00:00:50.400
Linear, which means in a straight line,

00:00:50.400 --> 00:00:53.310
to delineate, which means
to describe in detail

00:00:53.310 --> 00:00:54.660
or draw out borders

00:00:54.660 --> 00:00:57.480
and perhaps, obviously,
the word line itself.

00:00:57.480 --> 00:00:59.190
But let's dive into align

00:00:59.190 --> 00:01:00.570
because if you're anything like me,

00:01:00.570 --> 00:01:03.633
you're wondering about
that G, why isn't it align?

00:01:04.560 --> 00:01:06.270
I will spare you the lecture

00:01:06.270 --> 00:01:08.580
and say simply that it came from French.

00:01:08.580 --> 00:01:09.570
Don't worry about it.

00:01:09.570 --> 00:01:12.510
We just don't say it, in the
same way we don't say the G

00:01:12.510 --> 00:01:16.680
in sign, or, at least, we
don't say it as a /g/ sound.

00:01:16.680 --> 00:01:18.180
I find this stuff fascinating.

00:01:18.180 --> 00:01:20.430
I could basically keep
talking about this forever,

00:01:20.430 --> 00:01:23.190
but I'm trying to keep these
videos short and snackable.

00:01:23.190 --> 00:01:26.610
So let's use align in some sentences.

00:01:26.610 --> 00:01:28.200
You can use it literally, right?

00:01:28.200 --> 00:01:29.550
Like, all lined up.

00:01:29.550 --> 00:01:30.840
When the planet's aligned,

00:01:30.840 --> 00:01:32.790
are powers we're at their greatest, right?

00:01:32.790 --> 00:01:35.190
You can draw a straight line from Neptune

00:01:35.190 --> 00:01:38.760
straight through to the
sun, straight enough.

00:01:38.760 --> 00:01:41.223
The planets aligned,

00:01:42.540 --> 00:01:45.900
but you can also use it
figuratively, non literally

00:01:45.900 --> 00:01:47.685
to say that people agree.

00:01:47.685 --> 00:01:50.520
Jamelle and I aligned on the fact

00:01:50.520 --> 00:01:53.610
that the cereal milk is
the best part of breakfast.

00:01:53.610 --> 00:01:56.550
Here we are, in fact, in agreement,

00:01:56.550 --> 00:01:59.310
in alignment, in fact,
I'll write that down.

00:01:59.310 --> 00:02:00.900
So this is the noun form.

00:02:00.900 --> 00:02:05.900
We've added -ment to turn it
into a noun, in alignment.

00:02:06.030 --> 00:02:07.980
And one last sentence.

00:02:07.980 --> 00:02:11.220
Supriya had to align
with the other rebels.

00:02:11.220 --> 00:02:14.310
She had to get in line,
they had to link up.

00:02:14.310 --> 00:02:17.340
So I hope you and I are
all aligned on the meaning

00:02:17.340 --> 00:02:19.470
of this word, because I am out of time.

00:02:19.470 --> 00:02:22.140
Until the next one,
you can learn anything.

00:02:22.140 --> 00:02:22.973
David, out.


Regulate

WEBVTT
Kind: captions
Language: en

00:00:00.210 --> 00:00:01.890
- [David] All right,
wordsmiths, what's up?

00:00:01.890 --> 00:00:04.530
The word of the day today is regulate.

00:00:04.530 --> 00:00:07.923
It means to make rules
that control something.

00:00:08.880 --> 00:00:10.680
I'll throw in a 10-second music break.

00:00:10.680 --> 00:00:15.000
Tell me if you can identify
any other common English words

00:00:15.000 --> 00:00:17.220
that start with reg.

00:00:17.220 --> 00:00:19.882
All right, here we go, music break.

00:00:19.882 --> 00:00:28.444
(groovy music made by my wonderful colleague Walt)

00:00:30.150 --> 00:00:33.180
All right, so some
related words are regular,

00:00:33.180 --> 00:00:34.620
regiment, regime.

00:00:34.620 --> 00:00:38.130
All of these words are
related to control or order.

00:00:38.130 --> 00:00:40.440
Regulate comes from the Latin root reg,

00:00:40.440 --> 00:00:42.690
meaning straight like a ruler.

00:00:42.690 --> 00:00:46.140
Something that's regular
follows a rule or a pattern.

00:00:46.140 --> 00:00:47.490
It's predictable.

00:00:47.490 --> 00:00:49.590
So something that is regulated

00:00:49.590 --> 00:00:51.450
has been controlled by a rule.

00:00:51.450 --> 00:00:53.310
That's what that ate part means.

00:00:53.310 --> 00:00:55.380
It's a word part that makes a verb,

00:00:55.380 --> 00:00:58.140
because regulate is a
verb, it's an action word.

00:00:58.140 --> 00:01:00.420
So let's use regulate in some sentences.

00:01:00.420 --> 00:01:02.317
You can use it in a literal sense like

00:01:02.317 --> 00:01:06.030
"This valve regulates how much
fuel goes into the engine."

00:01:06.030 --> 00:01:09.150
It is literally controlling
the rate of fuel release.

00:01:09.150 --> 00:01:12.240
But you can also use regulate
to refer to lawmaking.

00:01:12.240 --> 00:01:13.980
And I can use another word part

00:01:13.980 --> 00:01:16.470
to make this verb into a noun.

00:01:16.470 --> 00:01:18.300
Okay, so we've got the word regulate,

00:01:18.300 --> 00:01:20.710
and let me lop off the E on the end

00:01:21.960 --> 00:01:24.240
and add I-O-N.

00:01:24.240 --> 00:01:27.240
And now it's a noun, regulation.

00:01:27.240 --> 00:01:29.737
Another word for a legal rule.

00:01:29.737 --> 00:01:32.070
"State regulations only allow you to catch

00:01:32.070 --> 00:01:33.030
three fish a week."

00:01:33.030 --> 00:01:35.700
So here's two fisherfolk, doot, doot.

00:01:35.700 --> 00:01:39.810
This woman has three fish, so she's fine.

00:01:39.810 --> 00:01:41.340
This man has four fish,

00:01:41.340 --> 00:01:44.910
so he's probably gonna get a
fine from Fish and Wildlife

00:01:44.910 --> 00:01:47.130
because he didn't adhere
to the regulations.

00:01:47.130 --> 00:01:50.520
Sorry pal, you've been
canceled by the government.

00:01:50.520 --> 00:01:53.193
All right, you can learn
anything, David out.


Le Châtelier's principle

WEBVTT
Kind: captions
Language: en

00:00:01.176 --> 00:00:03.900
- [Instructor] Let's imagine a reaction

00:00:03.900 --> 00:00:05.400
that is in equilibrium.

00:00:05.400 --> 00:00:10.400
So A plus B, they can
react to form C plus D,

00:00:10.530 --> 00:00:11.850
or you could go the other way around.

00:00:11.850 --> 00:00:15.390
C plus D could react to form A plus B.

00:00:15.390 --> 00:00:17.670
And we assume that
they've all been hanging

00:00:17.670 --> 00:00:20.490
around long enough for
this to be in equilibrium

00:00:20.490 --> 00:00:24.060
so that the reaction that goes
from A plus B to C plus D,

00:00:24.060 --> 00:00:25.530
it's happening at the same rate

00:00:25.530 --> 00:00:29.790
as the reaction from C plus D to A plus B.

00:00:29.790 --> 00:00:31.800
Now what we're gonna do is imagine

00:00:31.800 --> 00:00:35.520
what would happen if we
disturb this equilibrium,

00:00:35.520 --> 00:00:37.980
and let's say we disturb this equilibrium

00:00:37.980 --> 00:00:42.960
by taking some C and D out of,

00:00:42.960 --> 00:00:45.210
let's say this was a
solution of some kind.

00:00:45.210 --> 00:00:50.190
So I just one time reduced
the concentration of C and D.

00:00:50.190 --> 00:00:51.900
Well, that disturbance, first of all,

00:00:51.900 --> 00:00:54.300
is going to throw us out of equilibrium,

00:00:54.300 --> 00:00:57.000
because now the reaction
that goes from C plus D

00:00:57.000 --> 00:01:00.060
to A plus B isn't going to
be able to happen as often.

00:01:00.060 --> 00:01:01.740
'Cause I just took C and D out,

00:01:01.740 --> 00:01:04.080
they're not going to bump
into each other enough

00:01:04.080 --> 00:01:07.470
to now form A and B at the same rate.

00:01:07.470 --> 00:01:09.870
So if you think about the net direction

00:01:09.870 --> 00:01:11.790
until we hit a new equilibrium,

00:01:11.790 --> 00:01:13.620
this is going to happen less.

00:01:13.620 --> 00:01:15.300
and this, initially, is going

00:01:15.300 --> 00:01:16.920
to be happening at the same amount.

00:01:16.920 --> 00:01:19.950
So you're going to have a net direction

00:01:19.950 --> 00:01:22.020
until we hit equilibrium again

00:01:22.020 --> 00:01:26.040
that goes from A plus B to C plus D.

00:01:26.040 --> 00:01:27.240
And then if you wait long enough,

00:01:27.240 --> 00:01:29.940
you're going to hit
back at an equilibrium.

00:01:29.940 --> 00:01:31.830
Now, let's think about what just happened.

00:01:31.830 --> 00:01:35.400
We disturbed the equilibrium
by taking C and D out.

00:01:35.400 --> 00:01:37.500
Until we hit our new equilibrium,

00:01:37.500 --> 00:01:41.010
we have more of the
reaction going from A plus B

00:01:41.010 --> 00:01:43.500
to C plus D on a net basis.

00:01:43.500 --> 00:01:44.790
And so it's relieving it.

00:01:44.790 --> 00:01:48.540
It's relieving the fact that
we took some C plus D out.

00:01:48.540 --> 00:01:51.840
And it's going to reestablish
a new equilibrium.

00:01:51.840 --> 00:01:54.720
If we took A plus B out, or A and B out,

00:01:54.720 --> 00:01:57.420
or even just one of them, A or B out,

00:01:57.420 --> 00:01:59.430
then you would have the opposite happen.

00:01:59.430 --> 00:02:01.560
But either way, if you disturb it,

00:02:01.560 --> 00:02:04.350
the system shifts to
relieve the disturbance

00:02:04.350 --> 00:02:06.570
and re-establish equilibrium.

00:02:06.570 --> 00:02:08.640
Now this principle, you might imagine,

00:02:08.640 --> 00:02:10.440
'cause it's been sitting
here the whole time,

00:02:10.440 --> 00:02:14.490
is Le Chatelier's Principle
that describes that.

00:02:14.490 --> 00:02:17.520
And it's not just by
disturbing it by changing,

00:02:17.520 --> 00:02:21.180
say, concentrations of
reactants or products.

00:02:21.180 --> 00:02:23.010
You could be changing other things.

00:02:23.010 --> 00:02:27.330
So for example, let's imagine
the reversible reaction,

00:02:27.330 --> 00:02:31.350
let's say A plus B, and let's
say these are all gases.

00:02:31.350 --> 00:02:34.650
So A plus B can react to form C,

00:02:34.650 --> 00:02:37.260
or C could react to,

00:02:37.260 --> 00:02:40.050
I guess you could imagine,
break up into A plus B.

00:02:40.050 --> 00:02:42.513
And let's imagine that
these are all gases.

00:02:43.470 --> 00:02:45.000
So let's assume that it's happening

00:02:45.000 --> 00:02:47.670
in a container of a certain size.

00:02:47.670 --> 00:02:50.580
And let's say that I were to shrink

00:02:50.580 --> 00:02:52.920
the volume of that container.

00:02:52.920 --> 00:02:56.160
What do you think is going
to happen in that situation?

00:02:56.160 --> 00:02:59.880
Well, if I shrink the
volume of that container,

00:02:59.880 --> 00:03:02.370
then you have a situation where A and B

00:03:02.370 --> 00:03:04.140
are going to bump into each other more.

00:03:04.140 --> 00:03:06.540
They're going to collide
into each other more.

00:03:06.540 --> 00:03:11.540
And so you are going to have a
net direction go in that one.

00:03:11.580 --> 00:03:16.580
You'll still have some C reacting
to break up into A and B,

00:03:16.650 --> 00:03:19.230
but you're going to have
more A and B reacting,

00:03:19.230 --> 00:03:21.810
bumping into each other,
colliding each other to form C,

00:03:21.810 --> 00:03:24.240
until we hit a new equilibrium.

00:03:24.240 --> 00:03:26.880
And notice what is happening there.

00:03:26.880 --> 00:03:30.060
When A plus B reacts to form C,

00:03:30.060 --> 00:03:33.150
it decreases the number of
particles in the container

00:03:33.150 --> 00:03:35.760
and it decreases the pressure.

00:03:35.760 --> 00:03:39.810
And so, eventually you're
going to hit a new equilibrium.

00:03:39.810 --> 00:03:41.760
But when you disturb that equilibrium

00:03:41.760 --> 00:03:43.470
by changing the volume,

00:03:43.470 --> 00:03:46.740
the system shifted to
relieve that disturbance.

00:03:46.740 --> 00:03:49.860
In that case, the disturbance
was an increased pressure

00:03:49.860 --> 00:03:52.233
and it reestablished the equilibrium.

00:03:53.070 --> 00:03:55.110
Let's imagine another reaction.

00:03:55.110 --> 00:03:58.590
Let's imagine A plus B.

00:03:58.590 --> 00:04:00.840
And let's say this is
an endothermic reaction.

00:04:00.840 --> 00:04:04.830
So I'm gonna treat energy
really as a reactant here.

00:04:04.830 --> 00:04:07.324
Just to make it clear that
this is an endothermic reaction

00:04:07.324 --> 00:04:10.470
that could form C plus D.

00:04:10.470 --> 00:04:13.710
Or you could have C plus D react

00:04:13.710 --> 00:04:15.750
to form A plus B plus energy.

00:04:15.750 --> 00:04:18.180
So the reaction that starts with C plus D

00:04:18.180 --> 00:04:20.370
and forms A plus B in energy,

00:04:20.370 --> 00:04:23.010
well, that's going to be exothermic.

00:04:23.010 --> 00:04:25.800
So let's imagine what would happen here,

00:04:25.800 --> 00:04:27.900
and let's imagine it's at equilibrium,

00:04:27.900 --> 00:04:30.180
but then we disturb that equilibrium.

00:04:30.180 --> 00:04:32.610
What happens if we
disturb that equilibrium

00:04:32.610 --> 00:04:36.570
by adding more energy over here?

00:04:36.570 --> 00:04:38.837
Well, if I add more energy,

00:04:38.837 --> 00:04:40.410
it's going to be easier

00:04:40.410 --> 00:04:43.710
for this endothermic reaction to occur,

00:04:43.710 --> 00:04:46.110
and so it's going to
disturb the equilibrium

00:04:46.110 --> 00:04:49.140
in that direction right over there.

00:04:49.140 --> 00:04:53.370
And so you're going to have
that energy really get used up

00:04:53.370 --> 00:04:55.590
to form more C and D.

00:04:55.590 --> 00:04:57.570
You could imagine the other way.

00:04:57.570 --> 00:05:00.660
What happens if I were
to take energy away?

00:05:00.660 --> 00:05:05.660
Well, you need energy for A and
B to react to form C plus D.

00:05:05.700 --> 00:05:08.040
So if you were to take energy away,

00:05:08.040 --> 00:05:10.860
then the reaction that starts with A and B

00:05:10.860 --> 00:05:12.600
is going to happen less.

00:05:12.600 --> 00:05:15.180
And so you're gonna have a net direction

00:05:15.180 --> 00:05:19.110
with C plus D reacting to form A plus B

00:05:19.110 --> 00:05:21.540
until you hit a new equilibrium.

00:05:21.540 --> 00:05:23.430
But the important thing to realize here

00:05:23.430 --> 00:05:25.050
is in every situation,

00:05:25.050 --> 00:05:26.700
whether we're disturbing the equilibrium

00:05:26.700 --> 00:05:29.550
by changing concentration,
by changing volume,

00:05:29.550 --> 00:05:31.380
and therefore changing pressure,

00:05:31.380 --> 00:05:33.750
or you're adding or taking away energy,

00:05:33.750 --> 00:05:36.300
which you could do in the form
of changing the temperature,

00:05:36.300 --> 00:05:39.900
the system shifts to
relieve that disturbance

00:05:39.900 --> 00:05:42.510
and re-establish a new equilibrium,

00:05:42.510 --> 00:05:45.303
which, once again, is Le
Chatelier's Principle.


Reversible reactions and equilibrium

WEBVTT
Kind: captions
Language: en

00:00:00.630 --> 00:00:02.130
- [Instructor] Let's imagine a reaction

00:00:02.130 --> 00:00:06.270
where we start with the reactants A and B,

00:00:06.270 --> 00:00:11.270
and they react to form
the products C and D.

00:00:12.660 --> 00:00:16.350
Now, it turns out that
in certain situations,

00:00:16.350 --> 00:00:19.290
the reaction could go the other way.

00:00:19.290 --> 00:00:22.470
You could start with C + D,

00:00:22.470 --> 00:00:27.470
and those could react
to end up with A + B.

00:00:27.660 --> 00:00:29.490
So when you have a reaction like this,

00:00:29.490 --> 00:00:31.230
that could go in either direction,

00:00:31.230 --> 00:00:33.870
we call that a reversible reaction.

00:00:33.870 --> 00:00:35.700
And that's why the title of this video,

00:00:35.700 --> 00:00:38.430
Reversible Reactions and Equilibrium.

00:00:38.430 --> 00:00:42.390
And one way to say that it
could go in either direction is

00:00:42.390 --> 00:00:46.620
to write it like this, A + B.

00:00:46.620 --> 00:00:48.720
And we use these half arrows.

00:00:48.720 --> 00:00:50.160
So it could go in that direction,

00:00:50.160 --> 00:00:53.340
or it could go in this direction.

00:00:53.340 --> 00:00:56.250
You could go to C + D.

00:00:56.250 --> 00:00:58.410
And what's going to happen is

00:00:58.410 --> 00:01:02.640
the reaction is going to
go in both directions.

00:01:02.640 --> 00:01:06.600
So A + B is going to react to form C + D,

00:01:06.600 --> 00:01:11.600
and C + D is going to react to form A + B.

00:01:11.610 --> 00:01:12.690
And at some point,

00:01:12.690 --> 00:01:15.090
you're going to be hitting an equilibrium.

00:01:15.090 --> 00:01:17.820
That's the point at which the
forward reaction is happening

00:01:17.820 --> 00:01:19.740
at the same rate as,

00:01:19.740 --> 00:01:22.530
I guess you could consider it
to be the backward reaction,

00:01:22.530 --> 00:01:25.650
going from C + D to A + B.

00:01:25.650 --> 00:01:27.270
Now, once you're at equilibrium,

00:01:27.270 --> 00:01:29.460
it doesn't mean that the reactions stop.

00:01:29.460 --> 00:01:33.960
It just means that the rate of
going from A + B to C + D is

00:01:33.960 --> 00:01:38.960
the same as the rate of
going from C + D to A + B.

00:01:39.120 --> 00:01:41.640
This is a really important
thing to realize.

00:01:41.640 --> 00:01:43.890
A common misconception
is that people think,

00:01:43.890 --> 00:01:47.880
at equilibrium, somehow
these reactions stop.

00:01:47.880 --> 00:01:49.320
That is not the case.

00:01:49.320 --> 00:01:52.050
It's just that the rate
of the forward reaction

00:01:52.050 --> 00:01:56.460
and the backward reaction
has now become the same rate.

00:01:56.460 --> 00:02:00.840
So even though you continue
to have A + B forming C + D,

00:02:00.840 --> 00:02:04.800
you have the same rate at
which C + D is now also going

00:02:04.800 --> 00:02:07.740
and forming A + B.

00:02:07.740 --> 00:02:11.520
Another misconception here
is that the concentrations

00:02:11.520 --> 00:02:14.670
of A + B and C + D, once
you're in equilibrium,

00:02:14.670 --> 00:02:16.410
they would've stabilized,

00:02:16.410 --> 00:02:20.460
but it's not necessarily that
the concentrations are equal.

00:02:20.460 --> 00:02:22.080
The point at which we're in equilibrium,

00:02:22.080 --> 00:02:25.290
you might have a much lower
concentration of C + D

00:02:25.290 --> 00:02:27.960
than A + B, or the other way around.

00:02:27.960 --> 00:02:31.200
What equilibrium is telling
us is that at equilibrium,

00:02:31.200 --> 00:02:33.450
the forward rate of reaction is equal

00:02:33.450 --> 00:02:36.603
to the backward rate of reaction.


Catalysts

WEBVTT
Kind: captions
Language: en

00:00:00.180 --> 00:00:01.013
- [Instructor] In this video,

00:00:01.013 --> 00:00:04.050
we're gonna talk a little
bit about catalysts.

00:00:04.050 --> 00:00:08.430
So let's first imagine
that we have two reactants,

00:00:08.430 --> 00:00:09.930
and I'm going to simplify things

00:00:09.930 --> 00:00:12.210
with these overly simplified drawings.

00:00:12.210 --> 00:00:15.720
So let's say you have this
reactant right over here,

00:00:15.720 --> 00:00:17.580
and I'm drawing it that way for a reason.

00:00:17.580 --> 00:00:20.370
And then let's say I have this reactant

00:00:20.370 --> 00:00:23.940
that looks something like this.

00:00:23.940 --> 00:00:26.340
And obviously if we're talking
about a chemical reaction,

00:00:26.340 --> 00:00:28.260
we're not usually talking about just

00:00:28.260 --> 00:00:29.820
two different molecules.

00:00:29.820 --> 00:00:34.170
We're talking about many
trillions of molecules

00:00:34.170 --> 00:00:37.020
that are oftentimes in
some form of a solution.

00:00:37.020 --> 00:00:40.770
But here we're just giving an
example of one of each types

00:00:40.770 --> 00:00:42.780
of the reactant molecules.

00:00:42.780 --> 00:00:47.010
So let's imagine that if they are able to

00:00:47.010 --> 00:00:50.190
run into each other with sufficient energy

00:00:50.190 --> 00:00:53.040
and with the right
orientation, they're going

00:00:53.040 --> 00:00:55.200
to bond with each other.

00:00:55.200 --> 00:00:58.800
So these two reactants would react

00:00:58.800 --> 00:01:02.460
to form this product that looks like this.

00:01:02.460 --> 00:01:07.460
And obviously, as I mentioned,
this is a oversimplification,

00:01:07.500 --> 00:01:10.530
but it gives you the general idea.

00:01:10.530 --> 00:01:15.530
So it might form a molecule
that looks like that.

00:01:15.540 --> 00:01:19.230
Now, as we mentioned, it
has to have the right energy

00:01:19.230 --> 00:01:21.420
and the right orientation.

00:01:21.420 --> 00:01:26.420
So we can think about this
in terms of an energy diagram

00:01:26.527 --> 00:01:30.180
right over here, where in
this axis, let's call this

00:01:30.180 --> 00:01:33.180
the progress,

00:01:33.180 --> 00:01:36.633
progress of reaction.

00:01:37.770 --> 00:01:41.673
And in this axis, let's just say energy.

00:01:43.470 --> 00:01:45.150
Energy.

00:01:45.150 --> 00:01:47.730
Now we have our reactants

00:01:47.730 --> 00:01:49.950
that are at a certain
energy level when they are

00:01:49.950 --> 00:01:52.200
left to their own devices.

00:01:52.200 --> 00:01:56.910
But if they have enough
energy added to the system,

00:01:56.910 --> 00:01:59.640
they are able to react.

00:01:59.640 --> 00:02:01.950
And then after they react,

00:02:01.950 --> 00:02:04.350
the product will have a certain energy.

00:02:04.350 --> 00:02:05.550
So this is a reaction where we've had

00:02:05.550 --> 00:02:07.680
to put energy into the reaction

00:02:07.680 --> 00:02:11.490
'cause the products have a
higher energy than the reactants.

00:02:11.490 --> 00:02:13.110
So this is the prod.

00:02:13.110 --> 00:02:14.520
In this case, there's just one product,

00:02:14.520 --> 00:02:15.750
let's call it products.

00:02:15.750 --> 00:02:18.273
And let's call this reactants.

00:02:19.380 --> 00:02:21.330
Now this hump over here where we have

00:02:21.330 --> 00:02:23.640
to put even more energy than we end up

00:02:23.640 --> 00:02:26.280
with our products at the end, we call

00:02:26.280 --> 00:02:29.200
that the activation energy, the energy

00:02:29.200 --> 00:02:31.020
that you need in order

00:02:31.020 --> 00:02:34.320
to make this reaction
happen from left to right.

00:02:34.320 --> 00:02:38.613
So this right over here
is the activation energy.

00:02:39.870 --> 00:02:42.393
Activation energy.

00:02:43.230 --> 00:02:47.280
Now I said that this video was
going to be about catalysts.

00:02:47.280 --> 00:02:49.380
What does a catalyst do?

00:02:49.380 --> 00:02:51.750
Well, a catalyst can lower

00:02:51.750 --> 00:02:55.290
the activation energy for a reaction.

00:02:55.290 --> 00:02:57.450
It's not a part of the reaction.

00:02:57.450 --> 00:02:59.070
You could view it as a bystander.

00:02:59.070 --> 00:03:01.590
It's something that's
helping the reaction happen.

00:03:01.590 --> 00:03:04.110
It's not getting used up in the reaction,

00:03:04.110 --> 00:03:06.120
it's not getting produced in the reaction.

00:03:06.120 --> 00:03:08.340
It's just helping the reaction happen.

00:03:08.340 --> 00:03:11.730
And it would help it by
lowering that activation energy.

00:03:11.730 --> 00:03:13.980
So if you have the presence of a catalyst,

00:03:13.980 --> 00:03:16.380
it might look something like this.

00:03:16.380 --> 00:03:17.880
So all of a sudden you need less energy

00:03:17.880 --> 00:03:20.790
to get over this hump
and to form the products.

00:03:20.790 --> 00:03:24.120
Now what could a catalyst
actually be that does that?

00:03:24.120 --> 00:03:26.220
Well, we could think
about biological systems

00:03:26.220 --> 00:03:30.510
where a common catalyst
is an enzyme or enzymes.

00:03:30.510 --> 00:03:33.210
And one way that they lower
the activation energy,

00:03:33.210 --> 00:03:35.360
it could be providing a surface

00:03:35.360 --> 00:03:37.470
where the reactants can react.

00:03:37.470 --> 00:03:40.170
It could be to make it a
little bit easier for them

00:03:40.170 --> 00:03:42.043
to get in the right orientation.

00:03:42.043 --> 00:03:46.365
So for example, imagine
if you had a huge enzyme

00:03:46.365 --> 00:03:49.350
that looked something like this.

00:03:49.350 --> 00:03:53.550
And this once again is
an over simplification.

00:03:53.550 --> 00:03:57.750
And it just happened to be
that this part of the enzyme,

00:03:57.750 --> 00:04:01.560
it's able to bond to that first reactant.

00:04:01.560 --> 00:04:03.690
Lemme do that same color,

00:04:03.690 --> 00:04:05.250
to that first reactant

00:04:05.250 --> 00:04:09.570
and puts it into the right
orientation where this other part

00:04:09.570 --> 00:04:12.630
of the enzyme can bond
with that second reactant

00:04:12.630 --> 00:04:16.260
and puts it in the right
orientation so that you don't need

00:04:16.260 --> 00:04:19.500
quite as much energy for them to be able

00:04:19.500 --> 00:04:21.180
to react with each other.

00:04:21.180 --> 00:04:23.550
And you might say, well,
why do we even need these?

00:04:23.550 --> 00:04:25.230
Or why are enzymes even important?

00:04:25.230 --> 00:04:27.570
Remember, enzymes are type of catalyst.

00:04:27.570 --> 00:04:29.940
Well, it turns out that your body,

00:04:29.940 --> 00:04:33.930
or many biological systems need
a lot of reactions to occur,

00:04:33.930 --> 00:04:35.370
but without a catalyst,

00:04:35.370 --> 00:04:38.820
and in this case, in a biological
system without an enzyme,

00:04:38.820 --> 00:04:41.820
the temperature would have to
be too high, where all sorts

00:04:41.820 --> 00:04:43.680
of other bad things will happen.

00:04:43.680 --> 00:04:46.980
But by having catalysts,
in this case, an enzyme,

00:04:46.980 --> 00:04:49.740
it allows the reaction to
proceed, in this case from left

00:04:49.740 --> 00:04:52.860
to right, without having
the energy be so high

00:04:52.860 --> 00:04:55.620
that it's damaging to
the system as a whole.

00:04:55.620 --> 00:04:57.840
So it's a label to have
this reaction happen

00:04:57.840 --> 00:05:01.110
at a lower energy or in
this biological system

00:05:01.110 --> 00:05:02.373
at a lower temperature.


Electronegativity and bond type

WEBVTT
Kind: captions
Language: en

00:00:02.040 --> 00:00:03.420
- [Instructor]
Electronegativity is probably

00:00:03.420 --> 00:00:05.280
the most important concept to understand

00:00:05.280 --> 00:00:06.660
in organic chemistry.

00:00:06.660 --> 00:00:08.670
We're gonna use a definition
that Linus Pauling gives

00:00:08.670 --> 00:00:11.340
in his book, "The Nature
of the Chemical Bond".

00:00:11.340 --> 00:00:14.310
So Linus Pauling says
that electronegativity

00:00:14.310 --> 00:00:18.240
refers to the power of
an atom in a molecule

00:00:18.240 --> 00:00:20.700
to attract electrons to itself.

00:00:20.700 --> 00:00:22.290
So if I look at a molecule,

00:00:22.290 --> 00:00:25.238
I'm going to compare two
atoms in that molecule.

00:00:25.238 --> 00:00:28.200
I'm going to compare carbon to oxygen

00:00:28.200 --> 00:00:30.900
in terms of the electronegativity.

00:00:30.900 --> 00:00:33.060
And to do that, I need to
look over here in the right

00:00:33.060 --> 00:00:34.500
at the organic periodic table,

00:00:34.500 --> 00:00:36.240
which shows the elements
most commonly used

00:00:36.240 --> 00:00:38.340
in organic chemistry, and then in blue,

00:00:38.340 --> 00:00:41.220
it gives us the Pauling
scale for electronegativity.

00:00:41.220 --> 00:00:43.230
So Linus Pauling actually calculated

00:00:43.230 --> 00:00:44.909
electronegativity values for the elements

00:00:44.909 --> 00:00:46.980
and put them into the table,

00:00:46.980 --> 00:00:49.560
and that allows us to
compare different elements

00:00:49.560 --> 00:00:51.480
in terms of their electronegativities.

00:00:51.480 --> 00:00:53.228
For example, we are concerned with carbon,

00:00:53.228 --> 00:00:55.683
which has an electronegativity
value of 2.5,

00:00:57.000 --> 00:00:58.787
and we're going to compare that to oxygen,

00:00:58.787 --> 00:01:02.760
which has an electronegativity
value of 3.5.

00:01:02.760 --> 00:01:06.540
So oxygen is more
electronegative than carbon.

00:01:06.540 --> 00:01:09.300
And the definition tells us

00:01:09.300 --> 00:01:11.280
that if oxygen is more electronegative,

00:01:11.280 --> 00:01:14.880
oxygen has a greater power to
attract electrons to itself

00:01:14.880 --> 00:01:15.960
than carbon does.

00:01:15.960 --> 00:01:17.277
And so if you think about the electrons

00:01:17.277 --> 00:01:19.944
and the covalent bond
between carbon and oxygen

00:01:19.944 --> 00:01:22.643
that are shared, they're shared unequally,

00:01:22.643 --> 00:01:24.601
because oxygen is more electronegative.

00:01:24.601 --> 00:01:27.480
Oxygen's going to pull
those electrons in red

00:01:27.480 --> 00:01:28.950
closer to itself.

00:01:28.950 --> 00:01:31.440
And since electrons
are negatively charged,

00:01:31.440 --> 00:01:34.156
the oxygen's gonna get a little
bit more negative charge,

00:01:34.156 --> 00:01:35.332
and so it's going to have

00:01:35.332 --> 00:01:38.550
what we call a partial
negative charge on it.

00:01:38.550 --> 00:01:39.690
So partial negative,

00:01:39.690 --> 00:01:43.590
partial sign is a lowercase
Greek letter delta.

00:01:43.590 --> 00:01:45.990
And so the oxygen is partially negative.

00:01:45.990 --> 00:01:48.810
It's pulling the electrons
in red closer to itself.

00:01:48.810 --> 00:01:52.020
Another way to show the movement
of those electrons in red

00:01:52.020 --> 00:01:54.390
closer to the oxygen would
be this funny arrow here.

00:01:54.390 --> 00:01:56.550
So the arrow points in the
direction of the movement

00:01:56.550 --> 00:01:58.740
of the electrons in red.

00:01:58.740 --> 00:02:02.790
So carbon is losing some
of those electrons in red.

00:02:02.790 --> 00:02:05.700
Carbon is losing a little
bit of electron density.

00:02:05.700 --> 00:02:08.430
Carbon is losing a little
bit of negative charge.

00:02:08.430 --> 00:02:09.840
So carbon used to be neutral,

00:02:09.840 --> 00:02:12.330
but since it's losing a
little bit of negative charge,

00:02:12.330 --> 00:02:15.840
this carbon will end up being
partially positive like that.

00:02:15.840 --> 00:02:17.850
So the carbon is partially positive,

00:02:17.850 --> 00:02:20.100
and the oxygen is partially negative.

00:02:20.100 --> 00:02:22.620
That's a polarized situation, right?

00:02:22.620 --> 00:02:24.148
You have a little bit of
negative charge on one side,

00:02:24.148 --> 00:02:26.640
a little bit of positive
charge on the other side.

00:02:26.640 --> 00:02:28.710
So it's still a covalent bond,

00:02:28.710 --> 00:02:30.282
but it's a polarized covalent bond

00:02:30.282 --> 00:02:32.696
due to the differences
in electronegativities

00:02:32.696 --> 00:02:35.130
between those two atoms.

00:02:35.130 --> 00:02:37.169
Let's do a few more examples here

00:02:37.169 --> 00:02:39.830
where we show the differences
in electronegativity.

00:02:39.830 --> 00:02:42.540
So if I were thinking about a molecule

00:02:42.540 --> 00:02:44.700
that has two carbons in it,

00:02:44.700 --> 00:02:48.600
and I'm thinking about what
happens to the electrons in red,

00:02:48.600 --> 00:02:50.760
well, for this example,

00:02:50.760 --> 00:02:54.390
each carbon has the same value
for electronegativity, right?

00:02:54.390 --> 00:02:56.700
So the carbon in the
left has a value of 2.5.

00:02:56.700 --> 00:02:59.160
The carbon in the right
has a value of 2.5.

00:02:59.160 --> 00:03:02.520
That's a difference in
electronegativity of zero,

00:03:02.520 --> 00:03:05.460
which means that the electrons
in red aren't gonna move

00:03:05.460 --> 00:03:07.350
towards one carbon or
towards the other carbon.

00:03:07.350 --> 00:03:08.760
They're gonna stay in the middle,

00:03:08.760 --> 00:03:11.130
they're gonna be shared
between those two atoms.

00:03:11.130 --> 00:03:12.840
So this is a covalent bond,

00:03:12.840 --> 00:03:15.300
and there's no polarity
situation created here,

00:03:15.300 --> 00:03:17.610
since there's no difference
in electronegativity.

00:03:17.610 --> 00:03:22.170
So we call this a nonpolar
covalent bond, right?

00:03:22.170 --> 00:03:27.170
So this is a nonpolar
covalent bond, like that.

00:03:27.720 --> 00:03:29.340
Let's do another example.

00:03:29.340 --> 00:03:31.340
Let's compare carbon to hydrogen.

00:03:31.340 --> 00:03:33.142
So if I had a molecule

00:03:33.142 --> 00:03:35.779
and I have a bond between
carbon and hydrogen,

00:03:35.779 --> 00:03:39.630
and I want to know what
happens to the electrons in red

00:03:39.630 --> 00:03:42.960
between the carbon and the
hydrogen, we've seen that carbon

00:03:42.960 --> 00:03:44.860
has an electronegativity value of 2.5,

00:03:45.780 --> 00:03:49.087
and we go up here to hydrogen,
which has a value of 2.1,

00:03:50.340 --> 00:03:51.833
and so that's difference of 0.4.

00:03:53.460 --> 00:03:55.109
So there is a difference
in electronegativity

00:03:55.109 --> 00:03:58.050
between those two atoms, but
it's a very small difference.

00:03:58.050 --> 00:04:00.270
and so most textbooks
would consider the bond

00:04:00.270 --> 00:04:01.500
between carbon and hydrogen

00:04:01.500 --> 00:04:05.340
to still be a nonpolar covalent bond.

00:04:05.340 --> 00:04:06.173
All right, let's go ahead

00:04:06.173 --> 00:04:09.030
and put in the example
we did above, right.

00:04:09.030 --> 00:04:11.010
where we compared the electronegativies

00:04:11.010 --> 00:04:13.770
of carbon and oxygen, like that.

00:04:13.770 --> 00:04:15.564
When we looked up the
values, we saw that carbon

00:04:15.564 --> 00:04:18.780
had an electronegativity value of 2.5,

00:04:18.780 --> 00:04:22.470
and oxygen had a value of
3.5 for a difference of one.

00:04:22.470 --> 00:04:26.130
And that's enough to have a
polar covalent bond, right?

00:04:26.130 --> 00:04:30.160
This is a polar covalent bond

00:04:31.380 --> 00:04:33.330
between the carbon and the oxygen.

00:04:33.330 --> 00:04:35.850
So when we think about
the electrons in red,

00:04:35.850 --> 00:04:38.700
the electrons in red are
pulled closer to the oxygen,

00:04:38.700 --> 00:04:41.670
giving the oxygen a
partial negative charge,

00:04:41.670 --> 00:04:44.640
and since electron density is
moving away from the carbon,

00:04:44.640 --> 00:04:47.133
the carbon gets a partial positive charge.

00:04:48.582 --> 00:04:50.452
And so we can see that if your difference

00:04:50.452 --> 00:04:53.040
in electronegativity is one,

00:04:53.040 --> 00:04:55.440
it's considered to be
a polar covalent bond,

00:04:55.440 --> 00:04:58.530
and if your difference in
electronegativity is 0.4,

00:04:58.530 --> 00:05:00.720
that's considered to be
a nonpolar covalent bond.

00:05:00.720 --> 00:05:03.514
So somewhere in between
there must be the difference

00:05:03.514 --> 00:05:07.860
between non-polar covalent
bond and a polar covalent bond.

00:05:07.860 --> 00:05:11.730
And most textbooks will tell
you approximately somewhere

00:05:11.730 --> 00:05:13.680
in the 0.5 range.

00:05:13.680 --> 00:05:15.210
So if the difference in electronegativity

00:05:15.210 --> 00:05:17.430
is greater than 0.5, you
can go ahead and consider it

00:05:17.430 --> 00:05:19.620
to be mostly a polar covalent bond.

00:05:19.620 --> 00:05:22.770
If the difference in
electronegativity is less than 0.5,

00:05:22.770 --> 00:05:25.800
we would consider that to
be a nonpolar covalent bond.

00:05:25.800 --> 00:05:28.380
Now, I should point out that
we're using the Pauling scale

00:05:28.380 --> 00:05:29.730
for electronegativity here,

00:05:29.730 --> 00:05:31.170
and there are several different scales

00:05:31.170 --> 00:05:32.220
for electronegativity.

00:05:32.220 --> 00:05:34.740
So these numbers are not absolute.

00:05:34.740 --> 00:05:36.371
These are more relative differences,

00:05:36.371 --> 00:05:39.630
and it's the relative
difference in electronegativity

00:05:39.630 --> 00:05:41.970
that we care the most about.

00:05:41.970 --> 00:05:43.413
Let's do another example.

00:05:45.350 --> 00:05:47.880
Let's compare oxygen to hydrogen.

00:05:47.880 --> 00:05:51.120
So let's think about what
happens to the electrons

00:05:51.120 --> 00:05:52.720
between oxygen and hydrogen.

00:05:52.720 --> 00:05:55.890
So the electrons in red here.

00:05:55.890 --> 00:05:57.150
All right, so we've already seen

00:05:57.150 --> 00:05:59.550
the electronegativity values
for both of these atoms.

00:05:59.550 --> 00:06:04.550
Oxygen had a value of 3.5, and
hydrogen had a value of 2.1.

00:06:05.670 --> 00:06:08.580
So that's an electronegativity
difference of 1.4.

00:06:08.580 --> 00:06:11.520
So this is a polar covalent bond.

00:06:11.520 --> 00:06:13.703
Since oxygen is more
electronegative than hydrogen,

00:06:13.703 --> 00:06:16.510
the electrons in red are going
to move closer to the oxygen.

00:06:16.510 --> 00:06:19.830
so the oxygen's going to get
a partial negative charge,

00:06:19.830 --> 00:06:22.740
and the hydrogen's gonna get
a partial positive charge,

00:06:22.740 --> 00:06:23.573
like that.


London dispersion forces introduction

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:01.590
- [Instructor] What we're
going to do in this video

00:00:01.590 --> 00:00:04.410
is start talking about forces that exist

00:00:04.410 --> 00:00:08.790
between even neutral atoms
or neutral molecules.

00:00:08.790 --> 00:00:11.130
And the first of these
intermolecular forces

00:00:11.130 --> 00:00:15.390
we will talk about are
London dispersion forces.

00:00:15.390 --> 00:00:16.980
So it sounds very fancy,

00:00:16.980 --> 00:00:18.510
but it's actually a pretty interesting

00:00:18.510 --> 00:00:20.760
and almost intuitive phenomenon.

00:00:20.760 --> 00:00:22.860
So we are used to thinking about atoms

00:00:22.860 --> 00:00:24.450
and let's just say we have a neutral atom,

00:00:24.450 --> 00:00:26.940
so it has the same number
of protons and electrons,

00:00:26.940 --> 00:00:29.340
and so that's all those
are all the protons

00:00:29.340 --> 00:00:31.800
and the neutrons in the nucleus.

00:00:31.800 --> 00:00:34.620
And then it'll have a cloud of electrons.

00:00:34.620 --> 00:00:36.271
So I'm just imagining all these electrons

00:00:36.271 --> 00:00:37.339
kind of jumping around.

00:00:37.339 --> 00:00:39.900
That's how I'm going to represent it.

00:00:39.900 --> 00:00:41.370
And let's imagine,

00:00:41.370 --> 00:00:43.110
and this is definitely not drawn to scale,

00:00:43.110 --> 00:00:45.990
the nucleus would actually
be much smaller if it was.

00:00:45.990 --> 00:00:48.658
But let's say that there is an
adjacent atom right over here

00:00:48.658 --> 00:00:50.100
and it's also neutral.

00:00:50.100 --> 00:00:52.440
Maybe it's the same type of
atom, it could be different,

00:00:52.440 --> 00:00:53.880
but we're gonna say it's neutral.

00:00:53.880 --> 00:00:57.000
And it also has an electron cloud.

00:00:57.000 --> 00:01:00.210
And so if these are
both neutral in charge,

00:01:00.210 --> 00:01:02.700
how would they be attracted to each other?

00:01:02.700 --> 00:01:05.850
And that's what London dispersion
forces actually explain.

00:01:05.850 --> 00:01:09.240
Because we have observed
that even neutral atoms

00:01:09.240 --> 00:01:12.987
and neutral molecules can
get attracted to each other.

00:01:12.987 --> 00:01:15.810
And the way to think about it is electrons

00:01:15.810 --> 00:01:18.870
are constantly jumping
around probabilistically.

00:01:18.870 --> 00:01:21.480
They're in this probability density cloud

00:01:21.480 --> 00:01:24.240
where electron could be
anywhere at any given moment,

00:01:24.240 --> 00:01:27.000
but they're not always going
to be evenly distributed.

00:01:27.000 --> 00:01:30.810
You can imagine that there is
a moment where that left atom

00:01:30.810 --> 00:01:32.910
might look like this, just for a moment

00:01:32.910 --> 00:01:35.250
where most of, or maybe slightly more

00:01:35.250 --> 00:01:37.800
of the electrons are spending
time on the left side

00:01:38.682 --> 00:01:41.100
of the atom than on the right side.

00:01:41.100 --> 00:01:43.320
So maybe it looks something like that.

00:01:43.320 --> 00:01:45.300
And so for that brief moment,

00:01:45.300 --> 00:01:47.520
you have a partial negative charge.

00:01:47.520 --> 00:01:50.370
This is the Greek letter
delta, lower case delta,

00:01:50.370 --> 00:01:53.310
which is used to denote partial charge.

00:01:53.310 --> 00:01:57.390
And on this side, you might
have a partial positive charge.

00:01:57.390 --> 00:01:59.340
Because remember, when it
was evenly distributed,

00:01:59.340 --> 00:02:00.771
the negative charge was offset

00:02:00.771 --> 00:02:03.120
by the positive charge of the nucleus.

00:02:03.120 --> 00:02:04.530
But here on the right side,

00:02:04.530 --> 00:02:05.850
because there's fewer electrons here,

00:02:05.850 --> 00:02:08.070
maybe you have a partial
positive on the left side,

00:02:08.070 --> 00:02:09.510
you have where most of the electrons

00:02:09.510 --> 00:02:11.760
are in that moment, partial negative.

00:02:11.760 --> 00:02:16.440
Now what might this induce
in the neighboring atom?

00:02:16.440 --> 00:02:17.273
Think about that.

00:02:17.273 --> 00:02:18.106
Pause the video.

00:02:18.106 --> 00:02:20.740
Think about what might happen
in the neighboring atom then?

00:02:21.780 --> 00:02:24.930
Well, we know that like
charges repel each other

00:02:24.930 --> 00:02:27.570
and opposite charges attract each other.

00:02:27.570 --> 00:02:30.210
So if we have a partial
positive charge out here

00:02:30.210 --> 00:02:32.790
on the right side of this left atom,

00:02:32.790 --> 00:02:34.740
well then the negative electrons

00:02:34.740 --> 00:02:38.040
might be attracted to
it in this right atom.

00:02:38.040 --> 00:02:40.230
So these electrons here
might actually be pulled

00:02:40.230 --> 00:02:42.540
a little bit to the left.

00:02:42.540 --> 00:02:45.120
So they might be pulled
a little bit to the left.

00:02:45.120 --> 00:02:50.120
And so that will induce
what is called a dipole.

00:02:50.430 --> 00:02:52.830
So now you'll have a
partial negative charge

00:02:52.830 --> 00:02:54.630
on the left side of this atom,

00:02:54.630 --> 00:02:58.500
and then a partial positive
charge on the right side of it.

00:02:58.500 --> 00:03:01.520
And we already had a
randomly occurring dipole

00:03:01.520 --> 00:03:04.230
on the left-hand side, but
then that would've induced

00:03:04.230 --> 00:03:06.030
a dipole on the right-hand side.

00:03:06.030 --> 00:03:08.730
A dipole is just when you
have the separation of charge

00:03:08.730 --> 00:03:11.100
where you have your
positive negative charges

00:03:11.100 --> 00:03:14.340
at two different parts
of a molecule or an atom

00:03:14.340 --> 00:03:16.410
or really, anything.

00:03:16.410 --> 00:03:18.450
But in this world, then all of a sudden,

00:03:18.450 --> 00:03:21.240
these two characters are
going to be attracted

00:03:21.240 --> 00:03:23.100
to each other or the atoms

00:03:23.100 --> 00:03:24.810
are going to be attracted to each other.

00:03:24.810 --> 00:03:29.460
And this attraction that
happens due to induced dipoles,

00:03:29.460 --> 00:03:34.460
that is exactly what London
dispersion forces is all about.

00:03:34.500 --> 00:03:36.480
You can actually call
London dispersion forces

00:03:36.480 --> 00:03:39.630
is induced dipole, induced dipole forces.

00:03:39.630 --> 00:03:41.430
They become attracted to each other

00:03:41.430 --> 00:03:44.340
because of what could start
out as a temporary imbalance

00:03:44.340 --> 00:03:47.670
of electrons, but then it induces
a dipole in the other atom

00:03:47.670 --> 00:03:50.430
or the other molecule, and
then they get attracted.

00:03:50.430 --> 00:03:52.350
So the next question you might ask is,

00:03:52.350 --> 00:03:54.270
how strong can these forces get?

00:03:54.270 --> 00:03:59.270
And that's all about a
notion of polarizability.

00:04:00.180 --> 00:04:04.020
How easy is it to polarize
an atom or molecule?

00:04:04.020 --> 00:04:08.550
And generally speaking, the
more electrons you have.

00:04:08.550 --> 00:04:13.550
So the larger the electron
cloud, larger electron cloud,

00:04:13.890 --> 00:04:18.000
electron cloud, which
is usually associated

00:04:18.000 --> 00:04:22.323
with molar mass, so usually, molar mass,

00:04:23.490 --> 00:04:26.460
then the higher polarizability
you're gonna have,

00:04:26.460 --> 00:04:27.840
'cause you're just gonna
have more electrons

00:04:27.840 --> 00:04:28.673
to play around with.

00:04:28.673 --> 00:04:31.890
If this was a helium atom,
which has a relatively small

00:04:31.890 --> 00:04:34.230
electron cloud, you couldn't have

00:04:34.230 --> 00:04:36.030
a significant imbalance.

00:04:36.030 --> 00:04:39.480
At most, you might have
two electrons on one side,

00:04:39.480 --> 00:04:41.640
which would cause some imbalance.

00:04:41.640 --> 00:04:44.730
But on the other hand,
imagine a much larger atom

00:04:44.730 --> 00:04:46.770
or a much larger molecule,

00:04:46.770 --> 00:04:49.080
you could have much more
significant imbalances.

00:04:49.080 --> 00:04:52.110
Three, four or five, 50 electrons.

00:04:52.110 --> 00:04:54.690
And that would create a
stronger temporary dipole,

00:04:54.690 --> 00:04:58.170
which would then induce a
stronger dipole in the neighbors.

00:04:58.170 --> 00:04:59.820
That could domino

00:04:59.820 --> 00:05:02.670
through the entire
sample of that molecule.

00:05:02.670 --> 00:05:07.470
So for example, if you were
to compare some noble gases

00:05:07.470 --> 00:05:10.650
to each other, and so we
can look at the noble gases

00:05:10.650 --> 00:05:12.420
here on the right-hand side.

00:05:12.420 --> 00:05:15.450
If you were to compare the
London dispersion forces

00:05:15.450 --> 00:05:18.660
between say, helium and argon,

00:05:18.660 --> 00:05:19.560
which one would you think

00:05:19.560 --> 00:05:21.810
would have higher London
dispersion forces?

00:05:21.810 --> 00:05:23.610
A bunch of helium atoms
next to each other,

00:05:23.610 --> 00:05:26.580
or a bunch of argon
atoms next to each other?

00:05:26.580 --> 00:05:30.600
Well, the argon atoms have
a larger electron cloud,

00:05:30.600 --> 00:05:34.230
so they have higher polarizability.

00:05:34.230 --> 00:05:37.860
And so you're going to have
higher London dispersion forces.

00:05:37.860 --> 00:05:40.740
And you can actually see
that in their boiling points.

00:05:40.740 --> 00:05:45.450
For example, the boiling point of helium

00:05:45.450 --> 00:05:47.790
is quite low.

00:05:47.790 --> 00:05:52.790
It is negative 268.9 degrees Celsius

00:05:53.070 --> 00:05:55.680
while the boiling point of argon,

00:05:55.680 --> 00:05:58.320
it's still at a low
temperature by our standards,

00:05:58.320 --> 00:06:00.210
but it's a much higher temperature

00:06:00.210 --> 00:06:02.100
than the boiling point for helium.

00:06:02.100 --> 00:06:07.100
It's at negative 185.8 degrees Celsius.

00:06:07.980 --> 00:06:11.070
So one way to think about
this, if you were at say,

00:06:11.070 --> 00:06:15.360
negative 270 degrees Celsius,

00:06:15.360 --> 00:06:19.260
you would find a sample of
helium in a liquid state.

00:06:19.260 --> 00:06:21.060
But as you warm things up,

00:06:21.060 --> 00:06:26.060
as you get beyond negative
268.9 degrees Celsius,

00:06:26.220 --> 00:06:29.970
you're going to see that
those London dispersion forces

00:06:29.970 --> 00:06:32.490
that are keeping those
helium atoms together

00:06:32.490 --> 00:06:34.980
sliding past each other in a liquid state,

00:06:34.980 --> 00:06:37.260
they're going to be overcome

00:06:37.260 --> 00:06:40.680
by the energy due to the temperature.

00:06:40.680 --> 00:06:43.500
And so they're going to be able
to break free of each other.

00:06:43.500 --> 00:06:46.470
And essentially, the
helium is going to boil

00:06:46.470 --> 00:06:49.530
and you're going to enter into
a gaseous state, the state

00:06:49.530 --> 00:06:51.930
that most of us are used
to seeing helium in.

00:06:51.930 --> 00:06:56.010
But that doesn't happen for
argon until a good bit warmer.

00:06:56.010 --> 00:06:57.600
Still cold by our standards.

00:06:57.600 --> 00:07:00.060
And that's because it takes more energy

00:07:00.060 --> 00:07:03.390
to overcome the London
dispersion forces of argon

00:07:03.390 --> 00:07:08.390
because the argon atoms
have larger electron clouds.

00:07:10.350 --> 00:07:13.800
So generally speaking,
the larger the molecule,

00:07:13.800 --> 00:07:15.600
because it has a larger electron cloud,

00:07:15.600 --> 00:07:17.310
it'll have higher polarizability

00:07:17.310 --> 00:07:19.203
and higher London dispersion forces.


Endothermic and exothermic reactions

WEBVTT
Kind: captions
Language: en

00:00:00.420 --> 00:00:03.720
- [Narrator] So what we have
depicted here is a reaction.

00:00:03.720 --> 00:00:04.860
I have a beaker.

00:00:04.860 --> 00:00:07.350
In that beaker, I have molecules,

00:00:07.350 --> 00:00:09.060
I have these purple molecules.

00:00:09.060 --> 00:00:11.640
I also have these blue ones.

00:00:11.640 --> 00:00:14.970
And if I were to just leave
this beaker at room temperature

00:00:14.970 --> 00:00:17.259
in my laboratory, nothing
is going to happen.

00:00:17.259 --> 00:00:20.490
These molecules aren't going
to react with each other.

00:00:20.490 --> 00:00:24.690
But then if I add energy to
this, if I were to heat it up,

00:00:24.690 --> 00:00:26.460
then I can get it to react.

00:00:26.460 --> 00:00:28.230
And so that's what we have over here.

00:00:28.230 --> 00:00:32.340
The energy is used to break these bonds

00:00:32.340 --> 00:00:36.450
and then the bonds can reform
to form different molecules.

00:00:36.450 --> 00:00:37.590
So we have a reaction here.

00:00:37.590 --> 00:00:39.750
Here are the reactants,
here are the products.

00:00:39.750 --> 00:00:42.600
And I'm also going to
assume that as these bonds,

00:00:42.600 --> 00:00:46.230
as these new bonds form,
it also releases energy.

00:00:46.230 --> 00:00:48.450
And what we're going to
think about in this video

00:00:48.450 --> 00:00:50.400
is whether the energy

00:00:50.400 --> 00:00:54.030
that is released from this
reaction is greater than,

00:00:54.030 --> 00:00:57.030
or less than, than the
energy that we put into it.

00:00:57.030 --> 00:00:59.220
And depending on the answer to that,

00:00:59.220 --> 00:01:02.550
we would label this as
either an endothermic

00:01:02.550 --> 00:01:05.280
or an exothermic reaction.

00:01:05.280 --> 00:01:07.560
So let's think about
this a little bit more.

00:01:07.560 --> 00:01:10.687
So if you have a system,
and you might say,

00:01:10.687 --> 00:01:12.180
"What's a system?"

00:01:12.180 --> 00:01:15.510
Well, a system is really just a fancy way

00:01:15.510 --> 00:01:17.700
of saying the thing
that you are focused on.

00:01:17.700 --> 00:01:20.730
And you can define that
system in any which way.

00:01:20.730 --> 00:01:23.820
Here we will call our system this beaker

00:01:23.820 --> 00:01:25.890
that has the solution inside of it.

00:01:25.890 --> 00:01:27.870
So our system is going to include that,

00:01:27.870 --> 00:01:30.840
but it's not going to include the outside,

00:01:30.840 --> 00:01:33.930
the burner that we're
using to create the heat.

00:01:33.930 --> 00:01:35.460
It's just that beaker.

00:01:35.460 --> 00:01:39.060
So this is the system in either situation.

00:01:39.060 --> 00:01:42.330
And then we could also label
the things outside the system.

00:01:42.330 --> 00:01:44.940
We could call that the surroundings.

00:01:44.940 --> 00:01:47.940
Hopefully, that's an
intuitive thing to call it.

00:01:47.940 --> 00:01:52.560
And when we light the flame
underneath this beaker,

00:01:52.560 --> 00:01:54.930
were transferring energy
from the surroundings

00:01:54.930 --> 00:01:56.070
into the system.

00:01:56.070 --> 00:01:58.140
The law of conservation of energy,

00:01:58.140 --> 00:02:00.990
which is also known as the
first law of thermodynamics,

00:02:00.990 --> 00:02:05.730
tells us that energy can neither
be created nor destroyed.

00:02:05.730 --> 00:02:07.320
So if we're getting energy into a system,

00:02:07.320 --> 00:02:09.270
it has to come from someplace.

00:02:09.270 --> 00:02:12.420
In this situation, the energy is coming

00:02:12.420 --> 00:02:15.510
from our surroundings, but as we know,

00:02:15.510 --> 00:02:17.730
we're not just putting
energy into the system.

00:02:17.730 --> 00:02:20.970
When these new bonds are formed,
it's also releasing energy.

00:02:20.970 --> 00:02:23.610
In a situation where it's
releasing less energy

00:02:23.610 --> 00:02:24.480
than was put in,

00:02:24.480 --> 00:02:28.440
I'll do that with a less
wide arrow, like this,

00:02:28.440 --> 00:02:31.350
this we would call an
endothermic reaction.

00:02:31.350 --> 00:02:33.870
Even though some is being
released, on a net basis,

00:02:33.870 --> 00:02:38.070
you're putting more in than
you are actually getting out.

00:02:38.070 --> 00:02:39.900
Now, if you had it the other way around,

00:02:39.900 --> 00:02:42.480
where if you had your system here

00:02:42.480 --> 00:02:45.180
and you're putting in a certain amount

00:02:45.180 --> 00:02:47.850
of energy into the system,

00:02:47.850 --> 00:02:50.460
but you're getting a lot more
energy out of the system,

00:02:50.460 --> 00:02:53.740
I'll do that as a big arrow, like this,

00:02:53.740 --> 00:02:56.220
that's an arrow, that's not a house,

00:02:56.220 --> 00:02:58.290
if you have a big arrow, like this,

00:02:58.290 --> 00:03:02.202
well, now, this we would
call an exothermic,

00:03:02.202 --> 00:03:05.460
exothermic reaction.

00:03:05.460 --> 00:03:09.180
Let me box these off, so
that we don't get confused.

00:03:09.180 --> 00:03:10.920
Now, we can also understand this

00:03:10.920 --> 00:03:12.750
in terms of potential energy

00:03:12.750 --> 00:03:15.600
and how the reaction progresses.

00:03:15.600 --> 00:03:18.750
So on the horizontal axis,

00:03:18.750 --> 00:03:23.223
we'll call this reaction
progress, reaction progress.

00:03:25.470 --> 00:03:28.650
And then the vertical
axis is potential energy.

00:03:28.650 --> 00:03:31.770
Now, our system, before
we start heating it up,

00:03:31.770 --> 00:03:35.400
our system is going to be
at some potential energy

00:03:35.400 --> 00:03:37.680
and maybe it's just happy right there.

00:03:37.680 --> 00:03:40.380
But then we start putting
energy into the system.

00:03:40.380 --> 00:03:42.870
We're doing this right
over here by lighting

00:03:42.870 --> 00:03:44.520
that burner under it.

00:03:44.520 --> 00:03:47.520
So as we put energy into the system,

00:03:47.520 --> 00:03:50.010
the potential energy goes up.

00:03:50.010 --> 00:03:53.280
And that energy is used to
essentially break the bonds

00:03:53.280 --> 00:03:55.530
of these reactants.

00:03:55.530 --> 00:03:58.710
And then once those
molecular parts are all free

00:03:58.710 --> 00:04:01.530
of each other, they can
now reform new bonds.

00:04:01.530 --> 00:04:04.500
And if we're in an exothermic reaction,

00:04:04.500 --> 00:04:08.850
those new bonds are going to
be at a lower potential energy

00:04:08.850 --> 00:04:12.570
than the original bonds of the reactants.

00:04:12.570 --> 00:04:14.850
So one way to think about it here is,

00:04:14.850 --> 00:04:17.310
at this phase, we are putting in energy.

00:04:17.310 --> 00:04:19.320
This is the energy we're
putting into the system.

00:04:19.320 --> 00:04:22.770
And you can calculate it by
thinking about this arrow.

00:04:22.770 --> 00:04:25.800
And then once those
molecular parts reform,

00:04:25.800 --> 00:04:27.480
you are releasing energy.

00:04:27.480 --> 00:04:29.340
And so you could think of that height

00:04:29.340 --> 00:04:32.100
as the release of energy.

00:04:32.100 --> 00:04:34.110
And if you thought about
what the net energy

00:04:34.110 --> 00:04:35.670
that gets released is,

00:04:35.670 --> 00:04:37.320
well, that's going to be the difference

00:04:37.320 --> 00:04:39.180
between the potential energy

00:04:39.180 --> 00:04:40.980
as you're entering into the reaction

00:04:40.980 --> 00:04:42.780
and then your final potential energy.

00:04:42.780 --> 00:04:46.800
So this distance right over
here is the net energy.

00:04:46.800 --> 00:04:48.900
And in this case, it is the net energy

00:04:48.900 --> 00:04:51.300
that has actually been
released from the reaction.

00:04:51.300 --> 00:04:54.870
So this right over here
is an exothermic reaction.

00:04:54.870 --> 00:04:55.703
You might be wondering, "Well,

00:04:55.703 --> 00:04:57.900
"what would an endothermic
reaction look like?"

00:04:57.900 --> 00:04:58.980
Well, in that situation,

00:04:58.980 --> 00:05:00.210
and I'll just draw it really fast,

00:05:00.210 --> 00:05:03.540
it would have the same
labels on the chart,

00:05:03.540 --> 00:05:05.430
you would be putting energy in.

00:05:05.430 --> 00:05:07.830
So let's say, you have some molecules,

00:05:07.830 --> 00:05:12.060
energy in to break those
bonds, the bonds are broken,

00:05:12.060 --> 00:05:13.590
and now things reform,

00:05:13.590 --> 00:05:15.390
but they get to a higher potential energy

00:05:15.390 --> 00:05:17.070
than you were before.

00:05:17.070 --> 00:05:20.760
So here we're putting in a lot of energy,

00:05:20.760 --> 00:05:24.300
but then when those bonds,
when we have new bonds forming,

00:05:24.300 --> 00:05:27.933
that's not quite as much as
the energy that we put in.

00:05:28.830 --> 00:05:31.320
And so there's a net
amount that we put in.

00:05:31.320 --> 00:05:33.660
The net amount that we put
in is gonna be the difference

00:05:33.660 --> 00:05:34.590
between that and that.

00:05:34.590 --> 00:05:37.740
It's going to be this
height right over here.

00:05:37.740 --> 00:05:39.330
So this is exothermic

00:05:39.330 --> 00:05:41.703
and this is endothermic right over here.


Physical and chemical changes

WEBVTT
Kind: captions
Language: en

00:00:00.210 --> 00:00:01.950
- [Instructor] So what we have
are three different pictures

00:00:01.950 --> 00:00:05.910
of substances undergoing
some type of change.

00:00:05.910 --> 00:00:08.220
And what we're gonna
focus on in this video

00:00:08.220 --> 00:00:11.970
is classifying things as
either being physical changes

00:00:11.970 --> 00:00:14.010
or chemical changes.

00:00:14.010 --> 00:00:16.050
And you might already have
already thought about this

00:00:16.050 --> 00:00:18.780
or seen this in a previous science class,

00:00:18.780 --> 00:00:21.120
but when we talk about a physical change,

00:00:21.120 --> 00:00:23.490
we're talking about where
there could be a change

00:00:23.490 --> 00:00:25.890
in properties but we're
not having a change

00:00:25.890 --> 00:00:29.130
in the actual composition
of what we're talking about.

00:00:29.130 --> 00:00:30.870
While in a chemical change,

00:00:30.870 --> 00:00:34.020
you actually do have a
change in composition,

00:00:34.020 --> 00:00:37.680
how the different constituent
atoms and elements match up

00:00:37.680 --> 00:00:41.670
or connect or bond to each
other might be different.

00:00:41.670 --> 00:00:43.950
So my first question to
you is pause this video,

00:00:43.950 --> 00:00:45.690
and we have some ice melting here,

00:00:45.690 --> 00:00:49.050
we have some propane
combusting or burning here,

00:00:49.050 --> 00:00:52.410
and we have some iron rusting here.

00:00:52.410 --> 00:00:53.280
And I want you to think about

00:00:53.280 --> 00:00:54.960
which of these are physical changes

00:00:54.960 --> 00:00:57.360
and which of these are
chemical changes and why.

00:00:58.710 --> 00:01:01.560
All right, now let's first
think about this water,

00:01:01.560 --> 00:01:02.940
this ice melting.

00:01:02.940 --> 00:01:06.600
And if we wanted to write it
in fancy chemical language

00:01:06.600 --> 00:01:09.900
or chemistry language, we
could write this as H2O

00:01:09.900 --> 00:01:14.900
going from its solid form to
H2O going into its liquid form.

00:01:16.890 --> 00:01:19.500
Now we don't have a change in composition.

00:01:19.500 --> 00:01:20.370
In either state,

00:01:20.370 --> 00:01:22.440
whether you're looking
at this liquid water here

00:01:22.440 --> 00:01:24.990
or whether you're looking
at the solid water there,

00:01:24.990 --> 00:01:29.220
you'll see a bunch of water molecules.

00:01:29.220 --> 00:01:33.360
Each oxygen is still
bonded to two hydrogens

00:01:33.360 --> 00:01:36.480
and so you're not having
a change in composition,

00:01:36.480 --> 00:01:41.430
and so this over here
is a physical change.

00:01:41.430 --> 00:01:42.900
And if we kept heating that water up

00:01:42.900 --> 00:01:44.340
and it started to vaporize,

00:01:44.340 --> 00:01:46.680
that would also be a physical change.

00:01:46.680 --> 00:01:49.020
Whereas it turns into water vapor,

00:01:49.020 --> 00:01:52.140
you have your intermolecular
forces being overcome

00:01:52.140 --> 00:01:54.447
but the covalent bonds between the oxygens

00:01:54.447 --> 00:01:55.620
and the hydrogens,

00:01:55.620 --> 00:01:58.710
those aren't breaking
or forming in some way.

00:01:58.710 --> 00:02:00.990
So once again, when you
go from ice to water,

00:02:00.990 --> 00:02:01.823
physical change.

00:02:01.823 --> 00:02:04.860
From water to vapor, or you
could say from liquid to gas,

00:02:04.860 --> 00:02:08.400
that is also going to
be a physical change.

00:02:08.400 --> 00:02:10.560
One general rule of thumb,

00:02:10.560 --> 00:02:12.990
when you think about what's
going on on a microscopic level,

00:02:12.990 --> 00:02:15.090
and this is a general rule of
thumb, it doesn't always apply

00:02:15.090 --> 00:02:17.250
and we'll think about an
edge case in a little bit,

00:02:17.250 --> 00:02:21.840
is when you're overcoming
intermolecular forces,

00:02:21.840 --> 00:02:23.940
that tends to be a physical change.

00:02:23.940 --> 00:02:27.750
But if you have chemical
bonds forming or breaking,

00:02:27.750 --> 00:02:30.870
that would be a chemical change.

00:02:30.870 --> 00:02:33.840
Now let's think about what's
going on here with the propane.

00:02:33.840 --> 00:02:35.970
If you were to write the
chemical reaction here,

00:02:35.970 --> 00:02:40.710
it would be propane, C3H8 in gas form.

00:02:40.710 --> 00:02:43.020
It needs oxygen to combust,

00:02:43.020 --> 00:02:44.340
so for every mole of propane,

00:02:44.340 --> 00:02:48.840
we have five moles of
molecular oxygen in gas form.

00:02:48.840 --> 00:02:51.750
And then when it combusts,

00:02:51.750 --> 00:02:53.640
you're going to produce three,

00:02:53.640 --> 00:02:55.620
for every one mole of propane

00:02:55.620 --> 00:02:57.300
and five moles of molecular oxygen,

00:02:57.300 --> 00:03:02.130
you're gonna produce three
moles of carbon dioxide gas,

00:03:02.130 --> 00:03:07.130
and four moles of water
in vapor form as well.

00:03:07.770 --> 00:03:09.210
And so what you actually have

00:03:09.210 --> 00:03:11.880
is the bonds in those
molecules are actually breaking

00:03:11.880 --> 00:03:13.890
and then reforming.

00:03:13.890 --> 00:03:16.950
So you don't just have
physical change going on here,

00:03:16.950 --> 00:03:19.320
you have chemical change.

00:03:19.320 --> 00:03:21.690
Chemical change.

00:03:21.690 --> 00:03:22.530
One way to think about it,

00:03:22.530 --> 00:03:25.860
you had propane here before, C3H8,

00:03:25.860 --> 00:03:29.370
after the reaction, you no
longer have the propane here.

00:03:29.370 --> 00:03:32.280
What you actually see as
fire, which is fascinating,

00:03:32.280 --> 00:03:34.800
this is just very hot gas.

00:03:34.800 --> 00:03:36.540
And that very hot air that you're seeing,

00:03:36.540 --> 00:03:38.580
and there's going to be
some carbon dioxide in there

00:03:38.580 --> 00:03:41.190
and there's going to be
some water vapor in there,

00:03:41.190 --> 00:03:42.900
the reason why it's getting so hot

00:03:42.900 --> 00:03:46.470
is because this releases a lot of energy.

00:03:46.470 --> 00:03:50.370
Now let's think about what's
going on here with this iron.

00:03:50.370 --> 00:03:53.640
If I were to write this
as a chemical reaction;

00:03:53.640 --> 00:03:57.090
for every four moles of iron in solid form

00:03:57.090 --> 00:04:00.834
plus three moles of
molecular oxygen in gas form,

00:04:00.834 --> 00:04:04.170
and that would just be the
ambient oxygen around this iron,

00:04:04.170 --> 00:04:09.170
it is going to produce two
moles of iron oxide as a solid.

00:04:13.740 --> 00:04:15.750
And that's what you see
there in the orange,

00:04:15.750 --> 00:04:17.160
that is the iron oxide.

00:04:17.160 --> 00:04:21.030
So notice this reaction
is forming new ionic bonds

00:04:21.030 --> 00:04:22.920
in that ferrous oxide.

00:04:22.920 --> 00:04:24.480
And to undergo the reaction,

00:04:24.480 --> 00:04:28.290
we had to break the metallic
bonds of the solid iron

00:04:28.290 --> 00:04:31.710
and the covalent bonds
in the molecular oxygen.

00:04:31.710 --> 00:04:36.120
So anytime we are breaking and
making these chemical bonds,

00:04:36.120 --> 00:04:37.893
we have a chemical change.


Ionization energy trends

WEBVTT
Kind: captions
Language: en

00:00:00.540 --> 00:00:01.470
- [Narrator] We're now going to think

00:00:01.470 --> 00:00:04.320
about ionization energy trends.

00:00:04.320 --> 00:00:05.820
What's ionization energy?

00:00:05.820 --> 00:00:07.800
It's the energy required

00:00:07.800 --> 00:00:12.800
to remove the highest energy
electron from an atom.

00:00:13.140 --> 00:00:16.113
And to think about this,
let's look at some data.

00:00:16.950 --> 00:00:20.580
So right over here is ionization energy

00:00:20.580 --> 00:00:22.890
plotted against atomic number

00:00:22.890 --> 00:00:26.040
for elements in the
periodic table of elements.

00:00:26.040 --> 00:00:29.070
So first, we can look group by group.

00:00:29.070 --> 00:00:31.200
So for example, if we look at Group 1,

00:00:31.200 --> 00:00:33.390
that's the first column,

00:00:33.390 --> 00:00:36.060
the leftmost column in the
periodic table of elements,

00:00:36.060 --> 00:00:37.770
starting with hydrogen here,

00:00:37.770 --> 00:00:40.080
you can see that as we
go down that column,

00:00:40.080 --> 00:00:42.750
it looks like, generally speaking,

00:00:42.750 --> 00:00:46.260
our ionization energy is decreasing.

00:00:46.260 --> 00:00:48.870
For Group 2, we see a similar pattern,

00:00:48.870 --> 00:00:51.180
as we go down that second column,

00:00:51.180 --> 00:00:53.610
our ionization energy, generally speaking,

00:00:53.610 --> 00:00:56.100
it looks like there's a
few slight anomalies here,

00:00:56.100 --> 00:00:57.990
it looks like it's decreasing.

00:00:57.990 --> 00:01:02.370
So as you go down a group,
the data seems to imply

00:01:02.370 --> 00:01:04.950
that ionization energy decreases.

00:01:04.950 --> 00:01:07.500
It takes less and less energy to remove

00:01:07.500 --> 00:01:10.770
that highest energy electron.

00:01:10.770 --> 00:01:13.380
Now let's look at the periods.

00:01:13.380 --> 00:01:16.380
So remember, the periods are
the rows in the periodic table,

00:01:16.380 --> 00:01:19.470
so if we look at that second
row in the periodic table,

00:01:19.470 --> 00:01:22.470
as we go from left to right,

00:01:22.470 --> 00:01:24.420
it looks like, generally speaking,

00:01:24.420 --> 00:01:27.780
ionization energy is increasing.

00:01:27.780 --> 00:01:29.700
It becomes harder and harder to remove

00:01:29.700 --> 00:01:31.230
that highest energy electron.

00:01:31.230 --> 00:01:34.500
Now, there are some anomalies here.

00:01:34.500 --> 00:01:37.410
It looks like it briefly decreases,

00:01:37.410 --> 00:01:39.180
and it increases, briefly decreases,

00:01:39.180 --> 00:01:42.840
but the general trend is as
you go from left to right,

00:01:42.840 --> 00:01:46.680
along that period, energy is increasing.

00:01:46.680 --> 00:01:48.840
We see the same thing in Period 3,

00:01:48.840 --> 00:01:50.880
once again, there are some anomalies here,

00:01:50.880 --> 00:01:53.340
but the trend seems to generally hold.

00:01:53.340 --> 00:01:58.110
We could also look at Period
4, and so on and so forth.

00:01:58.110 --> 00:02:00.690
So if we think about ionization energy,

00:02:00.690 --> 00:02:05.490
what we saw is, as we go
down a group right over here,

00:02:05.490 --> 00:02:07.440
it becomes easier and easier

00:02:07.440 --> 00:02:10.350
to remove that highest energy electron,

00:02:10.350 --> 00:02:11.790
or another way to think about it

00:02:11.790 --> 00:02:16.650
is ionization energy decreases.

00:02:16.650 --> 00:02:19.740
If you go from left to right

00:02:19.740 --> 00:02:22.740
along a period right over here,

00:02:22.740 --> 00:02:27.740
we saw from the data, that
ionization energy increases.

00:02:28.560 --> 00:02:30.960
Now let's think about why this is.

00:02:30.960 --> 00:02:33.090
Well, if you look at this trend,

00:02:33.090 --> 00:02:34.710
or get an intuition for why this is,

00:02:34.710 --> 00:02:37.530
if you look at this trend
along a group over here,

00:02:37.530 --> 00:02:40.500
we already said that you're
gonna have the same number

00:02:40.500 --> 00:02:41.430
of valence electrons,

00:02:41.430 --> 00:02:44.790
but those valence electrons
are further and further out,

00:02:44.790 --> 00:02:47.100
they're at higher and
higher energy shells,

00:02:47.100 --> 00:02:49.380
and so you have a lot more shielding

00:02:49.380 --> 00:02:51.420
from all of those core electrons,

00:02:51.420 --> 00:02:52.980
so that causes some interference,

00:02:52.980 --> 00:02:55.680
we've already seen that
as you go down a group,

00:02:55.680 --> 00:02:58.320
your atomic radius increases,

00:02:58.320 --> 00:03:00.510
so you're also going to have less

00:03:00.510 --> 00:03:04.440
of that effective nuclear force,

00:03:04.440 --> 00:03:07.890
which is essentially how
much the force is between

00:03:07.890 --> 00:03:10.830
when you consider the nucleus,

00:03:10.830 --> 00:03:12.840
when you consider the shielding

00:03:12.840 --> 00:03:14.370
from the electrons in between,

00:03:14.370 --> 00:03:15.990
and when you think about the distance

00:03:15.990 --> 00:03:17.700
of those outer electrons.

00:03:17.700 --> 00:03:20.040
And so it makes sense that
it's easier and easier

00:03:20.040 --> 00:03:22.350
to remove the highest energy electron

00:03:22.350 --> 00:03:24.510
from say, caesium, because
it's further out there,

00:03:24.510 --> 00:03:28.410
there's more electrons
shielding it from that nucleus,

00:03:28.410 --> 00:03:31.440
even though there's a lot
of protons in that nucleus,

00:03:31.440 --> 00:03:34.410
than, say, in the case of hydrogen.

00:03:34.410 --> 00:03:38.430
Now, as you go from left
to right along a period,

00:03:38.430 --> 00:03:39.960
we already talked about the fact

00:03:39.960 --> 00:03:42.000
that you're adding electrons,

00:03:42.000 --> 00:03:46.260
but you're either backfilling
into a lower energy shell

00:03:46.260 --> 00:03:50.340
or you're adding at that
same outer valence shell.

00:03:50.340 --> 00:03:53.490
But as you're doing so, as
you're going from left to right,

00:03:53.490 --> 00:03:56.430
you have more and more protons.

00:03:56.430 --> 00:03:59.400
So those protons, as
you add more and more,

00:03:59.400 --> 00:04:01.500
you're gonna have a
stronger positive charge,

00:04:01.500 --> 00:04:04.620
it's gonna pull more and more
on those outer electrons.

00:04:04.620 --> 00:04:07.980
And remember, you have the
same number of core electrons,

00:04:07.980 --> 00:04:08.970
'cause you're just adding

00:04:08.970 --> 00:04:11.070
to the outer shells right over here,

00:04:11.070 --> 00:04:13.110
and so it's going to pull
harder and harder on them

00:04:13.110 --> 00:04:14.490
and bring them closer and closer.

00:04:14.490 --> 00:04:16.650
And we saw that atomic radii

00:04:16.650 --> 00:04:18.720
decreases as you go from left to right,

00:04:18.720 --> 00:04:22.020
and so it makes sense that
ionization energy increases.

00:04:22.020 --> 00:04:23.730
It's going to be harder and harder

00:04:23.730 --> 00:04:26.760
to pull off that highest energy electron,

00:04:26.760 --> 00:04:28.680
from say, bromine,

00:04:28.680 --> 00:04:31.143
than it would be from say, potassium.