ShmoopTube

00:03

Here’s your Shmoop du jour, brought to you by states of matter.

00:08

Chemistry has three, which is perfectly respectable. [Solid, liquid and a gas]

00:10

America’s just showing off.

00:13

Here’s our question:

00:15

Solid carbon dioxide is sometimes used to refrigerate foods and to make the fog that

00:19

emits from fog machines because carbon dioxide is a solid at low temperature.

00:25

When exposed to air, carbon dioxide immediately converts to a gas.

00:29

What is the direct conversion from a solid to a gas called?

00:33

And here are our potential answers...

00:38

This question is fairly straightforward, but just for fun, let’s look at all the different [Road sign for route to the answer]

00:42

phase transitions you might get thrown at you on a test.

00:45

Hopefully not literally. [Teacher throwing balled up paper at a student]

00:47

Matter exists in one of three states: solid, liquid, or gas.

00:52

The temperature of the matter and pressure on the matter will determine what state the

00:56

matter is in.

00:58

Matter can transition between states if the pressure or temperature of the matter changes, [Liquid pouring out of a soda bottle]

01:02

or if they’re standing in that one cool place where Utah, New Mexico, Arizona, and

01:06

Colorado meet.

01:07

The most common transitions we observe in daily life are solid to liquid and liquid

01:12

to gas, because these are the transitions that water undergoes at normal temperatures [Man sitting on a sofa with a water droplet]

01:17

and pressures.

01:18

If these are not the transitions you observe most frequently, you may be a life form from [People standing in a field and alien appears from a spacecraft]

01:23

another planet in which case please contact NASA so they can study you––no dissections

01:29

we promise.

01:30

However, all matter can undergo a transition between any two phases of matter if the temperature [Girl throwing darts at a board]

01:35

and pressure are in the right spot.

01:37

The question is asking us about a transition from a solid to a gas, which isn’t common

01:42

in water on earth but is the norm for carbon dioxide. [A river streaming with water]

01:46

And because scientists like graphs...really, here’s a graph showing how much we like

01:50

graphs compared to other people….there’s a graphical way to represent phase transitions. [People studying a graph]

01:56

This helps us see how transitions between any states of matter can occur, while having

02:00

all the added fun of being a graph!

02:05

Creatively called a “phase transition diagram,”––what? [Boy with a phase transition diagram]

02:10

We like graphs, not thinking of creative names for them–– this plot shows the state of

02:14

matter for CO2, the molecule in the question.

02:18

Each line between states on the graph represents a point where if the temperature or pressure

02:23

changes, the carbon dioxide will go from one state to another.

02:28

This gives us a total of six ways that matter can change states, because each change is

02:33

reversible.

02:34

Let’s take a look at what each change is called.

02:37

Going from solid to liquid is named “Thomas,” but goes by “Tom” for short. [Ice cubes melt into a puddle of water]

02:41

...Okay, it’s actually called melting, and going from liquid to solid is freezing.

02:47

Going from liquid to gas is boiling and going from gas to liquid is condensing [Person pours boiling water into a pan]

02:52

And going from solid to gas is sublimation and going from gas to solid is deposition

03:00

The question was asking what the transition from a solid to a gas is called, so the answer

03:05

is A. Sublimation. [Answer A circled green]

03:07

Answer B, melting is solid to liquid and answer D, boiling is liquid to gas.

03:12

And answer D, decomposition isn’t even a transition between states of matter, so we

03:16

can toss that one right into the compost bin. [Man throws decomposition into a compost bin]

03:19

We found the right answer and eliminated all the others, so our chemistry skills must be

03:23

sublimation!

03:25

...Whoops. [Chemistry skills explode]

03:26

We meant sublime.

03:27

Now we’ll never get those skills back...

Full Transcript