9:59:59.000,9:59:59.000


0:00:00.450,0:00:02.550
In this video, I want to[br]cover several topics

0:00:02.550,0:00:03.650
that are all related.

0:00:03.650,0:00:05.850
And on some level, they're[br]really simple, but on a whole

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other level, they tend to[br]confuse people a lot.

0:00:07.883,0:00:10.110
So hopefully we can[br]make some headway.

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So a good place to start-- let's[br]just imagine that I have

0:00:12.400,0:00:15.460
some type of container here.

0:00:15.460,0:00:18.130
Let's say that's my container[br]and inside of that container,

0:00:18.130,0:00:21.430
I have a bunch of[br]water molecules.

0:00:21.430,0:00:24.070
It's just got a bunch[br]of water molecules.

0:00:24.070,0:00:25.550
They're all rubbing against[br]each other.

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It's in its liquid form,[br]this is liquid water.

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and inside of the water[br]molecules, I

0:00:30.340,0:00:33.050
have some sugar molecules.

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Maybe I'll do sugar in[br]this pink color.

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So I have a bunch of sugar[br]molecules right here.

0:00:40.690,0:00:43.040
I have many, many more water[br]molecules though.

0:00:43.040,0:00:44.290
I want to make that clear.

0:00:44.290,0:00:49.420
I have many, many more water molecules in this container that we are dealing with.

0:00:49.420,0:00:55.660
Now in this type of situation,[br]we call, we call the thing that there's

0:00:55.660,0:01:00.440
more of, the solvent.

0:01:00.440,0:01:03.350
So in this case, there's more[br]water molecules and you can

0:01:03.350,0:01:07.990
literally just view more as[br]the number of molecules.

0:01:07.990,0:01:10.010
I'm not going to go into a whole[br]discussion of moles and

0:01:10.010,0:01:13.140
all of that because you may or[br]may not have been exposed to

0:01:13.140,0:01:15.670
that yet, but just imagine[br]whatever there's more of,

0:01:15.670,0:01:17.740
that's what we're going[br]to call the solvent.

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So in this case, water[br]is the solvent.

0:01:24.630,0:01:30.030
And whatever there is less of, so the more water is the solvent and in that case, that is the[br]in this case, that is the

0:01:30.030,0:01:32.730
sugar-- that is considered[br]the solute.

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this is the solute, so the sugar.

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It doesn't have to be sugar.

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It could be any molecule that[br]there's less of, in the water,

0:01:40.320,0:01:41.570
in this case,sugar.

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is the solute

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And we say that the sugar has[br]been dissolved into the water.

0:01:49.620,0:02:03.500
sugar,has been dissolved, dissolved into, into the water

0:02:03.500,0:02:06.420
And this whole thing right here,[br]the combination of the

0:02:06.420,0:02:10.229
water and the sugar molecules,[br]we call a solution.

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We call this whole[br]thing a solution.

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And a solution has a solvent[br]and the solute.

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The solvent is water.

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That's the thing doing the[br]dissolving and the thing that

0:02:21.110,0:02:23.220
is dissolved is the sugar.

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That's the solute.

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Now all of this may or may not[br]be review for you, but I'm

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doing it for a reason-- because[br]I want to talk about, I want to talk about

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the idea of diffusion, diffusion

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And the,the idea is actually[br]pretty straightforward.

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If I have, let's say,let's same[br]the same container.

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Let me do it in a slightly[br]different container here, just

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to talk about diffusion.

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We'll go back to water[br]and sugar--

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especially back to water.

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Let's say we have a container[br]here and let's say it just has

0:02:58.570,0:03:00.830
a bunch of-- let's say it just[br]has some air particles in it.

0:03:00.830,0:03:03.560
It could be anything-- oxygen[br]or carbon dioxide.

0:03:03.560,0:03:07.880
So let me just draw a couple[br]of air molecules here.

0:03:07.880,0:03:11.060
So let's say that that is a[br]gaseous-- just for the sake of

0:03:11.060,0:03:12.590
argument-- gaseous oxygen.

0:03:12.590,0:03:14.900
So each of this is an O2--[br]each of those, right?

0:03:14.900,0:03:16.900
And let's say that this is the[br]current configuration, that

0:03:16.900,0:03:19.710
all of this is a vacuum here[br]and that there's some

0:03:19.710,0:03:20.220
temperatures.

0:03:20.220,0:03:22.490
So these water molecules,[br]they have some

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type, some type of kinetic energy.

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They're moving in some type of[br]random directions right there.

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So my question is, what is going[br]to happen, what is goign to happen in this type

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of container?

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Well, any of these guys are[br]going to be randomly bumping

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into each other.

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They're more likely to bump into[br]things in this down-left

0:03:43.030,0:03:45.120
direction than they are in[br]the up-right direction.

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So if this guy was happening[br]to go in this down-left

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direction, he's going to bump[br]into something and then

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ricochet into the up-right[br]direction.

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But in the up-right[br]direction, there's

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nothing to bounce into.

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So in general, everything is[br]moving in random directions,

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but you're more likely[br]to be able to move in

0:04:00.250,0:04:01.000
the rightward direction.

0:04:01.000,0:04:02.500
When you go to the left, you're[br]more likely to bump

0:04:02.500,0:04:04.130
into each other, into something.

0:04:04.130,0:04:06.090
So it's almost common sense.

0:04:06.090,0:04:09.550
Over time, if you just let this[br]system come to some type

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of equilibrium-- I'm not[br]going to go into detail

0:04:11.580,0:04:12.340
on what that means.

0:04:12.340,0:04:14.340
You can watch the thermodynamics[br]videos if you'd

0:04:14.340,0:04:15.470
like to see that.

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You'll eventually see the[br]container will look

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something like this.

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I can't guarantee it.

0:04:20.200,0:04:22.500
There's some probability it[br]would actually stay like this,

0:04:22.500,0:04:25.920
but very likely that those five[br]particles are going to

0:04:25.920,0:04:27.970
get relatively spread out.

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This is diffusion and so it's[br]really just the spreading of

0:04:32.790,0:04:36.940
particles or molecules from[br]high concentration to low

0:04:36.940,0:04:39.140
concentration areas, right?

0:04:39.140,0:04:41.420
In this case, the molecules are[br]going to spread in that

0:04:41.420,0:04:43.780
direction from a high[br]concentration to a low

0:04:43.780,0:04:45.130
concentration area.

0:04:45.130,0:04:47.920
Now you're saying, Sal,[br]what is concentration?

0:04:47.920,0:04:51.060
And there's many ways to measure[br]concentration and you

0:04:51.060,0:04:54.120
can go into molarity and[br]molality and all of that.

0:04:54.120,0:04:57.830
But the very simple idea is, how[br]much of that particle do

0:04:57.830,0:04:59.900
you have per unit space?

0:04:59.900,0:05:02.780
So here, you have a lot of those[br]particles per unit space

0:05:02.780,0:05:04.550
and here you have very[br]few of those

0:05:04.550,0:05:05.850
particles per unit space.

0:05:05.850,0:05:09.230
So this is a high concentration[br]and that's a low

0:05:09.230,0:05:09.970
concentration.

0:05:09.970,0:05:12.740
So you could imagine other[br]experiments like this.

0:05:12.740,0:05:17.000
You could imagine a solution[br]like-- let's do

0:05:17.000,0:05:18.250
something like this.

0:05:18.250,0:05:21.570
let me make

0:05:21.570,0:05:22.820
Let's say I have[br]two containers.

0:05:22.820,0:05:25.440
let's see two container.

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Let's go back to the[br]solution situation.

0:05:27.230,0:05:29.720
This was a gas, but I started[br]off with that example so let's

0:05:29.720,0:05:31.432
stay with that example.

0:05:31.432,0:05:35.530
So let's say that I have a door[br]right there that's larger

0:05:35.530,0:05:38.370
than either the water or[br]the sugar molecules.

0:05:38.370,0:05:41.305
On either side, I have a bunch[br]of water molecules.

0:05:41.305,0:05:52.020
I have a bunch of water molecules on either side, just like that on either side

0:05:52.020,0:05:53.300
So I have a lot of[br]water molecules.

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So if I just had water molecules[br]here-- they're all

0:05:55.650,0:05:58.690
bouncing around in random[br]directions-- and so the odds

0:05:58.690,0:06:01.890
of a water molecule going this[br]way, equivalent to what odds of a

0:06:01.890,0:06:04.590
water molecule going that way,[br]assuming that both sides have

0:06:04.590,0:06:06.570
the same level of water[br]molecule, otherwise the

0:06:06.570,0:06:07.510
pressures would be different.

0:06:07.510,0:06:10.070
But let's say, you know that the top[br]of this is the same

0:06:10.070,0:06:11.170
as the top of this.

0:06:11.170,0:06:12.730
So there's no more pressure[br]going in one

0:06:12.730,0:06:13.790
direction or another.

0:06:13.790,0:06:17.240
So you know if,it for whatever reason, a[br]bunch of more water molecules

0:06:17.240,0:06:18.772
were going in the rightward[br]direction, then all of a

0:06:18.772,0:06:20.760
sudden this would fill up with[br]more water and we know that

0:06:20.760,0:06:22.620
that isn't likely to occur.

0:06:22.620,0:06:28.200
So this is,you know, this is just a solution, with or , this is just two containers of waters[br]of water.

0:06:28.200,0:06:30.340
Now let's put some[br]solute in it.

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Let's dissolve some solute in it[br]and let's say we do all the

0:06:33.230,0:06:35.630
dissolving on the[br]left-hand side.

0:06:35.630,0:06:40.620
So we put some sugar molecules[br]on the left-hand side.

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And these are small enough to[br]fit through this little pipe.

0:06:42.910,0:06:44.280
right, that's just one assumption[br]that I'm making.

0:06:44.280,0:06:45.120
So what's going to happen?

0:06:45.120,0:06:47.710
All of these things have some[br]type of kinetic energy.

0:06:47.710,0:06:52.630
They're all bouncing , they're all bouncing around.

0:06:52.630,0:06:56.250
Well, over time,you know, the water's[br]going back and forth.

0:06:56.250,0:06:57.600
This water molecule[br]might go that way.

0:06:57.600,0:07:00.040
That water molecule might go[br]that way, but they net out each

0:07:00.040,0:07:03.810
other out, but over time one of[br]these big sugar molecules

0:07:03.810,0:07:06.520
will be going in just the[br]right direction to go

0:07:06.520,0:07:08.470
through--maybe you know maybe this guy's,[br]instead of going that

0:07:08.470,0:07:10.380
direction, he starts off going[br]in that direction.

0:07:10.380,0:07:15.630
He goes just through this,throught this,uhm throught this tunnel[br]connecting this two

0:07:15.630,0:07:18.050
containers and he'll end[br]up there, right?

0:07:18.050,0:07:20.320
And this guy will still[br]be bouncing around.

0:07:20.320,0:07:23.570
There's some probability he goes[br]back, but there's still

0:07:23.570,0:07:25.420
more particles,more sugar particles[br]here than there.

0:07:25.420,0:07:31.350
So there's still more[br]probability that one of, so these

0:07:31.350,0:07:33.350
guys will go to that side[br]than one of these guys

0:07:33.350,0:07:34.340
will go to that side, that one of these guys will go to that side,

0:07:34.340,0:07:36.980
So you can imagine if you're[br]doing this with gazillions of

0:07:36.980,0:07:40.650
particles-- I'm only doing it[br]with four-- over time, the

0:07:40.650,0:07:43.440
particles will have spread out[br]so that their concentrations

0:07:43.440,0:07:44.550
are roughly equal.

0:07:44.550,0:07:46.950
So that maybe you'll have[br]two here over time.

0:07:46.950,0:07:49.430
But if, but when you're only dealing[br]with three or four or five

0:07:49.430,0:07:51.380
particles, there's some[br]probability it doesn't happen,

0:07:51.380,0:07:53.240
but when you're doing it with a[br]gazillion and they're super

0:07:53.240,0:07:56.810
small, it's a very, very,[br]very high likelihood.

0:07:56.810,0:07:59.590
But anyway, this whole process--[br]we went from a

0:07:59.590,0:08:02.460
container of high concentration[br]to a container

0:08:02.460,0:08:06.080
of low concentration and the[br]particles would have spread

0:08:06.080,0:08:08.530
from the low concentration[br]container to the high

0:08:08.530,0:08:09.590
concentration container.

0:08:09.590,0:08:11.130
So they diffused.

0:08:11.130,0:08:12.820
This is diffusion.

0:08:12.820,0:08:16.170
This is diffusion

0:08:16.170,0:08:18.880
And just so that we learn some[br]other words that tend to be

0:08:18.880,0:08:21.800
used with the idea of[br]diffusion-- when we started

0:08:21.800,0:08:24.260
off, this had a higher[br]concentration.

0:08:24.260,0:08:26.715
The left-hand side container[br]had higher concentration.

0:08:26.715,0:08:33.110
Higher concentration, higher concentration

0:08:33.110,0:08:34.130
It's all relative, right?

0:08:34.130,0:08:37.480
It's higher than this guy,higher concentration

0:08:37.480,0:08:39.505
And this right here had[br]a lower concentration.

0:08:39.505,0:08:42.799
Lower concentrarion

0:08:42.799,0:08:44.450
And there are words[br]for these things.

0:08:44.450,0:08:47.650
This solution with a high[br]concentration is called a

0:08:47.650,0:08:50.330
hypertonic solution.

0:08:50.330,0:08:51.730
Let me write that in yellow.

0:08:51.730,0:08:58.330
Hyoer, Hypertonic solution

0:08:58.330,0:09:01.120
Hyper, in general, meaning[br]having a lot of something,

0:09:01.120,0:09:02.620
having too much of something.

0:09:02.620,0:09:05.925
And this lower concentration[br]is hypo, hypotonic

0:09:05.925,0:09:13.720
Hypotonic solution,lower concentration

0:09:13.720,0:09:16.660
You might have heard maybe one[br]of your relatives, if they

0:09:16.660,0:09:20.730
haven't had a meal in awhile[br]say, I'm hypoglycemic.

0:09:20.730,0:09:22.230
That means that they have[br]not-- they're feeling

0:09:22.230,0:09:22.910
lightheaded.

0:09:22.910,0:09:24.800
There's not enough sugar in[br]their bloodstream and they

0:09:24.800,0:09:26.730
want to pass out so[br]they want a meal.

0:09:26.730,0:09:29.930
If you just had a candy bar,[br]maybe you're hyperglycemic--

0:09:29.930,0:09:32.930
or maybe you're just[br]hyper in general.

0:09:32.930,0:09:35.580
But, so, you know, so these are just good[br]prefixes to know, but

0:09:35.580,0:09:38.650
hypertonic-- you have[br]a lot of the solute.

0:09:38.650,0:09:40.510
You have a high concentration.

0:09:40.510,0:09:44.500
And then in hypotonic, not too[br]much of the solute so you have

0:09:44.500,0:09:46.010
a low concentration.

0:09:46.010,0:09:47.130
These are good words to know.

0:09:47.130,0:09:51.220
So in general, diffusion-- if[br]there's no barriers to the

0:09:51.220,0:09:54.790
diffusion like we had here, you[br]will have the solute go

0:09:54.790,0:09:58.820
from a high concentration or[br]hypertonic solution if they

0:09:58.820,0:10:03.490
can travel to a hypotonic[br]solution, to a hypo, where the

0:10:03.490,0:10:05.520
concentration is lower.

0:10:05.520,0:10:08.480
Now let's do an interesting[br]experiment here.

0:10:08.480,0:10:10.930
We've talked about diffusion and[br]so far we've been talking

0:10:10.930,0:10:14.530
about the diffusion of[br]the solute, right?

0:10:14.530,0:10:17.770
And in general-- and this is not[br]always the case-- if you

0:10:17.770,0:10:19.780
want to be as general as[br]possible, the solute is

0:10:19.780,0:10:22.400
whatever you have less of,[br]the solvent is whatever

0:10:22.400,0:10:23.510
you have more of.

0:10:23.510,0:10:26.600
And the most common solvent[br]tends to be water, but it

0:10:26.600,0:10:27.520
doesn't have to be water.

0:10:27.520,0:10:28.870
It could be some type[br]of alcohol.

0:10:28.870,0:10:31.390
It could be a...you, know it could be mercury.

0:10:31.390,0:10:34.880
It could be a whole set of[br]molecules, but water in most

0:10:34.880,0:10:38.130
biological or chemical systems[br]tends to be the

0:10:38.130,0:10:39.460
most typical solvent.

0:10:39.460,0:10:41.920
It's what other things[br]are dissolved into.

0:10:41.920,0:10:46.380
But what happens if we have a[br]tunnel where the solute is too

0:10:46.380,0:10:51.060
big to travel, but water is[br]small enough to travel?

0:10:51.060,0:10:55.370
Let's think about[br]that situation, let's think about the situation

0:10:55.370,0:10:57.090
In order to think about it,[br]I'm going to do something

0:10:57.090,0:10:58.830
interesting.

0:10:58.830,0:11:02.670
Let's say we have a[br]container here,let's say

0:11:02.670,0:11:03.950
Actually, I won't even[br]draw a container.

0:11:03.950,0:11:07.190
Let's just say we have an[br]outside environment that has a

0:11:07.190,0:11:09.260
bunch of water.

0:11:09.260,0:11:12.630
This is the outside environment[br]and then you have

0:11:12.630,0:11:13.880
some type of membrane.

0:11:13.880,0:11:19.400
you have some type of membrane here, that's a membrane

0:11:19.400,0:11:22.040
Water can go in and out[br]of this membrane.

0:11:22.040,0:11:23.190
So it's semi-permeable.

0:11:23.190,0:11:26.520
Well, it's permeable to water,[br]but the solute cannot go

0:11:26.520,0:11:27.110
through the membrane.

0:11:27.110,0:11:28.680
So let's say that the[br]solute is sugar.

0:11:28.680,0:11:33.060
So we have water on[br]the outside and

0:11:33.060,0:11:36.126
also inside the membrane.

0:11:36.126,0:11:39.380
So these are little small[br]water molecules.

0:11:39.380,0:11:43.950
This is a membrane right here.

0:11:43.950,0:11:46.520
And let's say that we have some[br]sugar molecules again--

0:11:46.520,0:11:47.560
I'm just picking on sugar.

0:11:47.560,0:11:48.760
It could have been anything.

0:11:48.760,0:11:51.050
So we have some sugar molecules[br]here that are just a

0:11:51.050,0:11:55.950
little bit bigger-- or they[br]could be a lot bigger.

0:11:55.950,0:11:57.750
Actually, they're a lot bigger[br]than water molecules.

0:11:57.750,0:11:59.700
You have a bunch of-- and I only[br]draw four, but you have a

0:11:59.700,0:12:01.210
gazillion of them, right?

0:12:01.210,0:12:03.470
You have that much more[br]water molecules.

0:12:03.470,0:12:05.325
I'm just trying to show you have[br]more water molecules than

0:12:05.325,0:12:06.290
sugar molecules.

0:12:06.290,0:12:07.645
And this membrane is[br]semi-permeable.

0:12:13.140,0:12:15.210
Permeable means it allows[br]things to pass.

0:12:15.210,0:12:18.070
Semi-permeables means it's[br]not completely permeable.

0:12:18.070,0:12:20.650
So semi-permeable-- in this[br]context, I'm saying I allow

0:12:20.650,0:12:22.440
water to pass through[br]the membrane.

0:12:22.440,0:12:28.850
So water can pass,[br]but sugar cannot.

0:12:28.850,0:12:30.100
Sugar is too large.

0:12:35.900,0:12:39.220
So if we were to zoom in on the[br]actual membrane itself--

0:12:39.220,0:12:40.580
maybe the membrane[br]looks like this.

0:12:40.580,0:12:41.980
I'm going to zoom in[br]on this membrane.

0:12:44.530,0:12:48.620
So it has little holes in the[br]membrane, just like that.

0:12:48.620,0:12:51.270
And maybe the water molecules[br]are about that size.

0:12:51.270,0:12:53.820
So they can go through[br]those holes.

0:12:53.820,0:12:56.250
So the water molecules can go[br]back and forth through the

0:12:56.250,0:13:01.520
holes, but the sugar molecules[br]are about that big.

0:13:01.520,0:13:04.990
So they cannot go through[br]that hole.

0:13:04.990,0:13:07.280
They're too big for this opening[br]right here to go back

0:13:07.280,0:13:08.830
and forth between them.

0:13:08.830,0:13:12.680
Now what do you think is going[br]to happen in this situation?

0:13:12.680,0:13:14.330
So first of all, let's[br]use our terminology.

0:13:14.330,0:13:15.720
Remember, sugar is our solute.

0:13:15.720,0:13:17.120
Water is our solvent.

0:13:17.120,0:13:18.930
Semi-permeable membrane.

0:13:18.930,0:13:21.400
Which side of the membrane[br]has a higher or lower

0:13:21.400,0:13:24.330
concentration of solute?

0:13:24.330,0:13:25.690
Well, the inside does.

0:13:25.690,0:13:27.060
The inside is hypertonic.

0:13:32.370,0:13:33.540
The outside has a lower

0:13:33.540,0:13:34.850
concentration so it's hypotonic.

0:13:44.850,0:13:47.680
Now, if these openings were big[br]enough, based on what we

0:13:47.680,0:13:51.330
just talked about-- these guys[br]are bouncing around, water is

0:13:51.330,0:13:53.700
travelling in either direction,[br]and equal

0:13:53.700,0:13:56.520
probability or-- actually[br]I'm going to talk

0:13:56.520,0:13:58.360
about that in a second.

0:13:58.360,0:14:01.660
If everything was wide open, it[br]would be equal probability,

0:14:01.660,0:14:03.780
but if it was wide open, these[br]guys eventually would bounce

0:14:03.780,0:14:06.450
their ways over to this side and[br]you'd probably end up with

0:14:06.450,0:14:08.500
equal concentrations[br]eventually.

0:14:08.500,0:14:10.710
And so you would have your[br]traditional diffusion, where

0:14:10.710,0:14:13.130
high concentration[br]of solute to low

0:14:13.130,0:14:14.530
concentrations of solute.

0:14:14.530,0:14:17.350
But in this case, these[br]guys-- they can't

0:14:17.350,0:14:18.330
fit through the hole.

0:14:18.330,0:14:20.160
Only water can go[br]back and forth.

0:14:20.160,0:14:25.180
If these guys were not here,[br]water would have an equal

0:14:25.180,0:14:28.780
likelihood of going in this[br]direction as they would be

0:14:28.780,0:14:33.940
going in that direction, a[br]completely equal likelihood.

0:14:33.940,0:14:40.090
But because these guys are on[br]the right-hand side of-- or in

0:14:40.090,0:14:42.290
this case, on the inside[br]of our membrane.

0:14:42.290,0:14:47.000
This is our inside of our[br]membrane zoomed up-- it's less

0:14:47.000,0:14:50.440
likely because these guys[br]might be in the approach

0:14:50.440,0:14:55.230
position of the holes-- that's[br]slightly less likely for water

0:14:55.230,0:14:58.110
to be in the approach position[br]for the holes so it's actually

0:14:58.110,0:15:02.720
more probable that water could[br]enter than water exit.

0:15:02.720,0:15:04.180
And I want to make[br]that very clear.

0:15:04.180,0:15:07.150
If these sugar molecules were[br]not here, obviously it's

0:15:07.150,0:15:09.830
equally likely for water to[br]go in either direction.

0:15:09.830,0:15:12.730
Now that these sugar molecules[br]are there, these sugar

0:15:12.730,0:15:15.290
molecules might be on[br]the right-hand side.

0:15:15.290,0:15:18.200
They might be blocking-- I guess[br]the best way to think

0:15:18.200,0:15:20.430
about it is blocking the[br]approach to the hole.

0:15:20.430,0:15:22.060
They'll never be able to go[br]through the hole themselves

0:15:22.060,0:15:24.490
and might not even be blocking[br]the hole, but they're going in

0:15:24.490,0:15:25.720
some random direction.

0:15:25.720,0:15:29.580
So if a water molecule was[br]approaching-- it's all

0:15:29.580,0:15:31.360
probabilistic and we're dealing[br]with gazillions of

0:15:31.360,0:15:34.610
molecules-- it's that much more[br]likely to be blocked to

0:15:34.610,0:15:35.360
get outside.

0:15:35.360,0:15:37.620
But the water molecules from the[br]outside-- there's nothing

0:15:37.620,0:15:40.170
blocking them to get in so[br]you're going to have a flow of

0:15:40.170,0:15:41.480
water inside.

0:15:41.480,0:15:44.310
So in this situation, with a[br]semi-permeable membrane,

0:15:44.310,0:15:45.700
you're going to have water.

0:15:45.700,0:15:49.280
You're going to have a net[br]inward flow of water.

0:15:49.280,0:15:51.430
And so this is kind[br]of interesting.

0:15:51.430,0:15:56.900
We have the solvent flowing from[br]a hypotonic situation to

0:15:56.900,0:15:59.600
a hypertonic solution,[br]but it's only

0:15:59.600,0:16:01.210
hypotonic in the solute.

0:16:07.650,0:16:11.620
But water-- if you flip it the[br]other way-- if you've used

0:16:11.620,0:16:15.290
sugar as the solvent, then you[br]could say, we're going from a

0:16:15.290,0:16:19.470
high concentration of water to[br]a low concentration of water.

0:16:19.470,0:16:20.370
I don't want to confuse[br]you too much.

0:16:20.370,0:16:23.090
This is what tends to confuse[br]people, but just think about

0:16:23.090,0:16:24.040
what's going to happen.

0:16:24.040,0:16:27.260
No matter in what situation,[br]the solution is going to do

0:16:27.260,0:16:30.000
what it can to try to[br]equilibriate the

0:16:30.000,0:16:30.680
concentration.

0:16:30.680,0:16:32.080
To make the concentrations[br]on both

0:16:32.080,0:16:33.710
sides as close as possible.

0:16:33.710,0:16:35.150
And it's not just some magic.

0:16:35.150,0:16:36.160
It's not like the[br]solution knows.

0:16:36.160,0:16:38.300
It's all based on probabilities[br]and these things

0:16:38.300,0:16:41.050
bumping around, but in this[br]situation, water is more

0:16:41.050,0:16:43.790
likely to flow into[br]the container.

0:16:43.790,0:16:46.700
So it's actually going to go[br]from the hypotonic side when

0:16:46.700,0:16:50.460
we talk about low concentration[br]of solute to the

0:16:50.460,0:16:53.690
side that has high[br]concentrations of solute, of

0:16:53.690,0:16:57.320
sugar-- and actually, if this[br]thing is stretchable, more

0:16:57.320,0:17:01.670
water will keep flowing[br]in and this membrane

0:17:01.670,0:17:04.420
will stretch out.

0:17:04.420,0:17:08.420
I won't go to too much detail[br]here, but this idea of water--

0:17:08.420,0:17:12.470
of the solvent-- if in this[br]case, water is the solvent--

0:17:12.470,0:17:15.150
of water as a solvent[br]diffusing through a

0:17:15.150,0:17:18.500
semi-permeable membrane,[br]this is called osmosis.

0:17:22.569,0:17:25.170
You've probably heard learning[br]by osmosis-- if you put a book

0:17:25.170,0:17:27.200
against your head, maybe it'll[br]just seep into your brain.

0:17:27.200,0:17:28.000
Same idea.

0:17:28.000,0:17:29.500
That's where the word[br]comes from.

0:17:29.500,0:17:33.570
This idea of water seeping[br]through membranes to try to

0:17:33.570,0:17:35.600
make concentrations[br]more equal.

0:17:35.600,0:17:38.370
So if you say, well, I have high[br]concentration here, low

0:17:38.370,0:17:39.490
concentration here.

0:17:39.490,0:17:43.020
If there was no membrane here,[br]these big molecules would

0:17:43.020,0:17:48.080
exit, but because there's this[br]semi-permeable membrane here,

0:17:48.080,0:17:48.680
they can't.

0:17:48.680,0:17:52.400
So the system just[br]probabilistically-- no magic

0:17:52.400,0:17:56.090
here-- more water will enter[br]to try to equilibriate

0:17:56.090,0:17:57.160
concentration.

0:17:57.160,0:18:01.970
Eventually-- if maybe there's a[br]few molecules out here-- not

0:18:01.970,0:18:06.440
as high concentration here--[br]eventually if everything was

0:18:06.440,0:18:08.970
allowed to happen fully, you'll[br]get to the point where

0:18:08.970,0:18:11.120
you have just as many--[br]you have just as high

0:18:11.120,0:18:13.650
concentration on this side as[br]you have on the right-hand

0:18:13.650,0:18:16.500
side because this right-hand[br]side is going to fill with

0:18:16.500,0:18:19.380
water and also probably become[br]a larger volume.

0:18:19.380,0:18:21.520
And then, once again, the[br]probabilities of a water

0:18:21.520,0:18:23.600
molecule going to the right and[br]to the left will be the

0:18:23.600,0:18:25.920
same and you'll get to some[br]type of equilibrium.

0:18:25.920,0:18:29.910
But I want to make it very[br]clear-- diffusion is the idea

0:18:29.910,0:18:33.130
of any particle going from[br]higher concentration and

0:18:33.130,0:18:35.740
spreading into a region that has[br]a lower concentration and

0:18:35.740,0:18:36.950
just spreading out.

0:18:36.950,0:18:41.240
Osmosis is the diffusion[br]of water.

0:18:41.240,0:18:44.210
And usually you're talking about[br]the diffusion of water

0:18:44.210,0:18:47.010
as a solvent and usually it's[br]in the context of a

0:18:47.010,0:18:51.260
semi-permeable membrane, where[br]the actual solute cannot

0:18:51.260,0:18:53.530
travel through the membrane.

0:18:53.530,0:18:55.800
Anyway, hopefully you've[br]found that useful and

0:18:55.800,0:18:57.880
not completely confusing.