So what happens when a liquid becomes a gas?
That's going to be the topic of this video.
At the end I'm going to talk about a huge mistake, major misconception that so many
people make when they're dealing with this topic.
So make sure you watch this to the end or if you think you already know all this stuff,
skip right to the end so you can learn what this mistake is and you will never ever ever
make it yourself.
Okay so let's start looking at this topic by examining something that I'm sure you've
seen happen in everyday life.
Let's say that I have a glass and I fill it up with water and I leave it on the kitchen
counter overnight.
In the morning I come and the glass used to be full and now most of the water looks like
it disappeared.
The water level is way down here.
What's happened?
Has the water just disappeared?
Where did it go?
Well as you probably know, what happens is the water evaporated which means the water
that was liquid turned in to gas and it just floated away, it floated off into the air.
This is evaporation and evaporation is a type of what we call vaporization.
Vaporization is that kind of catch-all term that we use whenever anytime a liquid turns
into a gas.
So the water disappearing from the glass of water overnight is an example of vaporization.
So this is like a real-world example that you can actually see.
Here's what I want to do now.
I want to pretend that we have a magic microscope or something and we can look at this glass
of water and we can zoom in on it and look at the atoms or molecules that make up this
glass of water so we can see what vaporization looks like at the molecular level.
It turns out that I don't want to just zoom in anywhere in this glass of water, I want
to zoom in on a very specific point.
I want to zoom in right here at the surface of the water where the water meets the air,
okay?
So let's take our magic microscope or whatever you want to call it and zoom in right on this
surface.
If we can actually do that, check it out, this is what we'd see.
We'd see a whole bunch of these kind of triangular things which are water molecules.
They are made up of one oxygen atom bound to two hydrogen atoms.
We have oxygen and two hydrogens.
And there would be a ton of them here.
The top of where these molecules are is the top of the water and then we have the air
above it.
Now there's something I can't really show with these water molecules here.
And that's that if we were really looking at this realistically, they'd all be moving
around a little bit.
They'd be jiggling around, some of them would be spinning around and turning and so imagine
if you can all these guys here are in constant, random motion bumping into each other and
they're all moving, swimming around, and jiggling around.
Now when vaporization happens, one of these guys is going to be moving a little bit faster
than the others and he or she is going to make it to the top, to the surface of the
water, and they're going to be moving fast enough that they can jump right out and away
from their buddies and float out in to the air.
And now this molecule that used to be a molecule of liquid water has become a molecule of water
gas.
And maybe down here, somebody else is moving a little bit fast, they're moving fast enough,
they make it up to the top and they're able to jump out and become gas and now we have
two molecules of water gas and then one more is moving fast enough that it can jump out
and become a gas.
So this is what happens when liquid water becomes gaseous water.
One of these guys are moving fast enough that it can jump out of the water and enter the
air becoming gas.
Now here is a huge mistake that so many people make when they're talking about vaporization.
Make sure you don't make this mistake yourself.
They think that when this water molecule turns into a gas, that somehow the atoms that make
it up come apart.
It looks like this when it's a liquid but then when it jumps out and becomes a gas,
the hydrogens and oxygens come apart and then this thing is made up of individual atoms,
atoms all split apart.
That does not happen, don't make that mistake.
The water molecule when it's in a gas looks exactly like it did when it was in water,
one oxygen and two hydrogens and that's what we call a phase change where liquid becomes
gas.
We call that a physical process not a chemical process because in a physical process you
don't alter the composition of the compound.
We still have one oxygen and two hydrogens even when the molecule is in gas form.
Okay now this isn't just true for water so don't think that's the only case.
What you learned is exactly the same for any other molecule.
Let's take a look at gasoline here.
Gasoline is a little bit more of a complex molecule.
It has eight carbons surrounded by eighteen hydrogens.
If we could look at a tiny sample of gasoline, liquid gasoline, it would look like this.
We have all these molecules and they'd be kind of packed together but I can't show this
particularly well.
They'd be moving around, one or two of them would be moving fast enough that they'd be
able to jump right out from their buddies and they'd float away in to the air and the
gasoline would vaporize just the same way the water molecules vaporized.
And again, what's true with molecules of water is no different with molecules of gasoline.
So it would be wrong, do not make this mistake, to think that gasoline when it's going from
liquid to vapor would somehow break apart into the atoms that make it up.
That doesn't happen.
The molecules that make up gasoline or water or anything look exactly the same when they're
in gas form as they do when they're in liquid form.
It's just they're not so close together moving around instead they broke away from their
buddies and they're floating out here in the air.
So that's what happens when liquid turns into a gas and never ever ever make a mistake thinking
that the atoms that make up a molecule come apart when it becomes a gas.
It doesn't happen.