In the last video we touched on the three states of matter
that are really most familiar to our everyday experience.
The solid, the liquid, and the gas.
And I kind of hinted that there is a fourth state, which
I don't cover, because it's usually not the domain of an
introductory chemistry course.
But a little bit of a discussion ensued on the
message board for that video.
So I thought I would at least touch on that fourth stage.
And that's plasma.
I'll do it in a suitably bright color.
Plasma.
And people consider it a fourth state because it has
some properties of gases.
In some ways it's almost a subset of gases.
But it also has properties of conductivity that you normally
wouldn't associate with a gas.
And just so you know, when you first hear it you think, oh
that's a fairly exotic thing, plasma.
And in the first video, I said it's only something that
occurs at high temperatures, which isn't
exactly 100% right.
It doesn't have to be at high temperatures.
I really should have said that under extenuating
circumstances where you have a very strong
electromagnetic field.
Or something has to happen to essentially bump the the
electrons, or move the electrons off of gases that
would've otherwise have kept their electrons.
So it's kind of analogous to what happens in metal.
When we talk about metal bonds, we talk about this
notion of a sea of electrons.
Let's say if we talked about iron.
What happens with most metals is that they have so many
electrons, and they are so willing to give them, that the
electrons just kind of float outside of the atoms
themselves and create this kind of big sea of electrons.
And then the atoms themselves become
positively charged ions.
Because they essentially donated some
electrons to the sea.
So they're attracted to the sea and that's what makes them
malleable and even more importantly what allows them
to conduct electricity.
But they're all really packed closely together and it's a
very dense structure.
Plasma is a situation where if you take gases, and remember,
in gases things are pretty far apart.
So you take a bunch of gases and they have
high kinetic energy.
Although, they don't have to be, that could be under very
low pressure.
But they're moving around and bumping into each other.
But they're not close to each other.
They don't have a fixed structure with each other.
Or they're not rubbing against each other like in
the case of a liquid.
But what happens in a plasma, or one situation is, that you
apply such a strong electromagnetic field that the
electrons want to disassociate.
So let's say these electrons start
bumping off of the plasma.
And so a solid has its own shape.
A plasma will take the shape of its container like a gas.
And sometimes it is described as an ionized gas.
And it's described as ionized because
electrons are bumped off.
And when the electrons are bumped off, the otherwise
neutral atoms now have positive charges.
And what this allows is, essentially a conduction of
electricity.
Because now these electrons are free to move.
You might say that sounds like a bizarre state of matter,
where does it exist?
Well, probably closest to home, it exists in lightning.
And that's worthy of an entire video.
But the idea is that you start having a huge potential
difference between the clouds and the ground.
And then because you have this huge voltage difference
between the two, you have electrons that are essentially
wanting to go into the ground.
You have a build-up of electrons up here that want to
go into the ground.
They can't because air is normally
a fairly bad conductor.
It's an insulator.
But what happens is because there's so much
electropotential here, the electrons that are close in
the molecules up here, at least how I visualize it,
their electrons want to escape from these clouds.
So their electrons start to want to move
away in the air molecules.
Whether you're talking about the air is a mixture of
oxygen, and nitrogen, and carbon dioxide.
They start wanting to get away from the clouds.
So they start disassociating and start forming
this ionized air.
And eventually, at some point, this happens to such a degree
that you can actually get conduction from the cloud to
the ground.
And that conduction is when the air is in a plasma state.
The conduction allows extremely high temperatures
and the electrons to flow all the way to the ground.
The other common example, you might see something like this,
well actually not like this, but at least a plasma state,
is in stars.
And that's because you have extremely strong
electromagnetic fields, extremely high pressure, and
in that type of environment, once again, I'm old super over
simplifying it, you can get to a state where the electrons
can get disassociated from things that otherwise wouldn't
want to give up their electrons.
I thought I would touch on that because it's an
interesting subject.
And it exists in the universe.
On the universal level, because stars are pretty much
all plasma, it is actually the most common state of matter in
the universe.
Although in our everyday life, we probably encounter solids,
liquids and gases a lot more.
And one other thing I want to maybe clarify from the last
video is, I talk about the bonding
between water molecules.
And let's say we're talking in the solid state.
So I have an oxygen, a hydrogen, a hydrogen.
And I have some electrons here, some electrons here.
Let's say there's another hydrogen here, an oxygen, and
a hydrogen.
Maybe there's an oxygen here.
That has hydrogen.
And then this has a hydrogen.
And it has two electrons, two electron pairs.
So I talked about the notion, and we talked about it many
times before.
That oxygen is so much more electronegative that it hogs
the electrons.
And so the oxygen side starts to have a
partial negative charge.
While the hydrogen side starts to have a
partial positive side.
Because with the hydrogen, essentially all of its
electrons are hanging out close to the oxygen, hydrogen
ends up just becoming like this proton that's
floating out there.
Because we said it doesn't even have
neutrons in most cases.
So this has a slightly positive charge.
This one has a positive charge.
And the positive polar end of the water molecule is
attracted to the negative polar end.
And I called it polar bonds, and it shows you my memory
from high school chemistry is not ideal, I really should
have called it hydrogen bonds.
So this is a hydrogen bond, and this is a hydrogen bond.
It's just a matter of the name I used.
I just want to clarify that because that is what's
typically used in your chemistry class.
I don't want to confuse you.
And that is just the bond that exists from a partially
positive hydrogen atom.
Because its electrons are hanging out near the oxygen.
And a partially negative oxygen atom
in the water molecule.
Because it has stolen all of these
electrons from the hydrogen.
You draw it like that, it's called a hydrogen bond.
And hydrogen bonds tend to form between hydrogen or
really only a handful of super electronegative atoms. And
that's nitrogen, fluorine, and oxygen.
And these are actually the three most electronegative
atoms. So the nitrogen, NH3, when it bonds with hydrogen,
is essentially so electronegative that you have
the same situation.
All the electrons hang out here, so you have a partial
negative charge, partial positive on the hydrogen ends.
Same thing with hydrogen fluorine.
You get the same HF.
You get the same type of hydrogen bonds.
And so in this case, these guys would be attracted to the
nitrogen part of other molecules and would form
hydrogen bonds.
I just want to get that out of the way.
And with that done, I think we can return to some of the
ideas of the last video and actually do some problems.
Let's take the case with water.
Actually, let me just state the problem first. So let's
say that we have a