Melting is the phase change from a solid to a liquid.

Sublimation is the phase change from a solid directly to a gas, skipping the liquid phase.

What is the triple point?

The triple point on a phase diagram is where the solid, liquid, and gas phases coexist.

What is a supercritical fluid?

A supercritical fluid has properties of both a gas and a liquid, existing beyond the critical temperature and pressure.

What determines whether a material's solid phase is more dense than its liquid phase?

Observing the melting point curve slope; for CO2, a positive slope indicates solid CO2 is denser.

Why does ice float on water?

Ice floats on water because liquid water has a higher density than solid ice.

What is the critical point?

The critical point is the temperature and pressure at which a substance becomes a supercritical fluid.

How do phase diagrams of CO2 and H2O differ?

CO2's melting point slope is positive, indicating solid is denser, while H2O's is negative, with liquid being denser.

When does sublimation occur for water?

Sublimation happens when water is at a pressure below its triple point.

What is the normal boiling point of water?

The normal boiling point is the temperature at which water boils at atmospheric pressure of 1 atm.

Phase Diagrams of Water & CO2 Explained - Chemistry - Melting, Boiling & Critical Point

00:10:27

https://www.youtube.com/watch?v=QrHlwgmMTq4

Ringkasan

TLDRThe video explains the phase diagrams of carbon dioxide (CO2) and water (H2O), starting with basic phase changes like melting, freezing, vaporization, condensation, sublimation, and deposition. It details CO2's phase diagram, highlighting the triple point where all phases coexist, the critical point where a supercritical fluid can form, and the concept of sublimation at standard pressure. CO2 sublimates directly from solid to gas at pressures below the triple point. Unlike many substances, solid CO2 is denser than its liquid due to a positive slope in the melting point curve. Water's phase diagram is introduced to show differences. It has a negative slope in the melting point line, meaning liquid water is denser than ice, explaining why ice floats. Key features like the critical point and normal boiling point where the atmospheric pressure is 1 atm are discussed, helping to understand how pressure and temperature affect phase transitions.

Takeaways

🧊 Melting is solid to liquid transition.
🔥 Vaporization is liquid to gas transition.
🌬️ Sublimation is solid to gas skipping liquid phase.
💧 Condensation is gas to liquid.
❄️ Deposition is reverse of sublimation: gas to solid.
🔺 Triple point is where solid, liquid, gas coexist.
⚖️ CO2 solid is denser than liquid due to positive melting slope.
🌡️ Critical point leads to supercritical fluid forms.
🌊 Ice floats because liquid water is denser.
🔄 H2O sublime below triple point pressure.
📈 Normal boiling point is at 1 atm pressure.
⬇️ H2O melting line has negative slope, unlike CO2.

Garis waktu

00:00:00 - 00:05:00
The video begins with an explanation of phase changes, including melting (solid to liquid), freezing (liquid to solid), vaporization (liquid to gas), and condensation (gas to liquid). Sublimation (solid to gas) and deposition (gas to solid) are also discussed. For CO2, sublimation occurs at standard pressure because it's below the triple point. The phase diagram's x-axis shows temperature, and the y-axis shows pressure, with critical points discussed, highlighting that beyond the critical temperature, gases can't be liquefied just by increasing pressure.
00:05:00 - 00:10:27
Moving on to the phase diagram for water, the melting point line has a negative slope, indicating differences in density between phases. At 1 atm, water transitions from solid to liquid to gas upon increasing temperature. Below the triple point, ice sublimates. Liquid water is denser than ice, explaining why ice floats. The critical point is where supercritical fluids form, having both gas and liquid properties. Boiling and melting points are further discussed, with 'normal' points being defined at 1 atm pressure.

Peta Pikiran

Pertanyaan yang Sering Diajukan

What is melting?
Melting is the phase change from a solid to a liquid.
What is sublimation?
Sublimation is the phase change from a solid directly to a gas, skipping the liquid phase.
What is the triple point?
The triple point on a phase diagram is where the solid, liquid, and gas phases coexist.
What is a supercritical fluid?
A supercritical fluid has properties of both a gas and a liquid, existing beyond the critical temperature and pressure.
What determines whether a material's solid phase is more dense than its liquid phase?
Observing the melting point curve slope; for CO2, a positive slope indicates solid CO2 is denser.
Why does ice float on water?
Ice floats on water because liquid water has a higher density than solid ice.
What is the critical point?
The critical point is the temperature and pressure at which a substance becomes a supercritical fluid.
How do phase diagrams of CO2 and H2O differ?
CO2's melting point slope is positive, indicating solid is denser, while H2O's is negative, with liquid being denser.
When does sublimation occur for water?
Sublimation happens when water is at a pressure below its triple point.
What is the normal boiling point of water?
The normal boiling point is the temperature at which water boils at atmospheric pressure of 1 atm.

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Teks

Gulir Otomatis:

00:00:00
in this video we're going to talk about
00:00:02
the phase diagrams for CO2 and water but
00:00:06
before we jump into that there are a few
00:00:09
things that we need to talk
00:00:11
about so let's go over phase changes if
00:00:14
you go from a solid to a
00:00:16
liquid what is this phase change called
00:00:20
going from a solid to a liquid this is
00:00:23
called
00:00:25
melting think of
00:00:27
ice when ice melts
00:00:31
into water it converts from a solid to a
00:00:33
liquid now what about the reverse liquid
00:00:36
to
00:00:37
solid so when water turns into ice it's
00:00:41
called
00:00:47
freezing now what about going from a
00:00:49
liquid to a
00:00:51
gas going from a liquid to a gas is
00:00:54
known as vaporization
00:01:03
now what about gas to a
00:01:06
liquid this is called
00:01:09
condensation now let's say if you place
00:01:11
a cold glass cup in a humid
00:01:15
environment you'll notice that water
00:01:17
condenses on the outside of the cup
00:01:21
you'll see like water droplets that's
00:01:23
the water vapor in the air condensing
00:01:25
into a
00:01:28
liquid now what about the conversion
00:01:30
from a solid directly into a gas
00:01:33
skipping the liquid
00:01:35
phase this is known as
00:01:40
sublimation a good example of
00:01:41
sublimation is dry ice
00:01:44
CO2 if you ever watch a YouTube video on
00:01:46
dry ice if you see solid
00:01:50
CO2 notice that it converts directly
00:01:53
into a gas it doesn't liquefy at room
00:01:56
temperature or rather at 1 atm at normal
00:02:00
pressure it goes directly from a solid
00:02:03
to a gas that's why it's called dry ice
00:02:06
now if you think about the other one gas
00:02:08
to a
00:02:09
solid this is simply the reverse of
00:02:12
sublimation this is called
00:02:15
deposition that's when the gas goes
00:02:17
directly back into the solid
00:02:21
form now let's start with the phase
00:02:24
diagram for
00:02:28
CO2 so on the x- axis we have uh the
00:02:31
temperature and the pressure is on the Y
00:02:35
AIS and typically the graph
00:02:38
looks something like
00:02:47
this so that's just a rough
00:02:50
sketch so here we have the
00:02:54
solid here is the liquid phas and here's
00:02:56
the gas phas
00:03:01
and here is the standard pressure at 1
00:03:06
atm the point where the solid liquid and
00:03:09
gas phases
00:03:10
coexist is called the triple
00:03:14
point the line between the solid and
00:03:16
liquid phase is known as the melting
00:03:19
point
00:03:20
line because to go from a solid to a
00:03:23
liquid it's melting and going backwards
00:03:26
from a liquid to a solid it's freezing
00:03:31
now the line between the liquid and the
00:03:33
gas phase is called the bowling Point
00:03:36
curve going from a liquid to a gas we
00:03:38
set it's uh vaporization and gas to a
00:03:42
liquid is uh
00:03:47
condensation now at 1 atm if you
00:03:51
increase the temperature for CO2 notice
00:03:53
that it goes directly from a solid to a
00:03:55
gas so CO2 sublimes
00:03:59
notice that at 1 atm the pressure is
00:04:03
below the triple point if the pressure
00:04:05
was above the triple point it would go
00:04:07
from a solid to a liquid to a gas but at
00:04:10
standard pressure it's below the triple
00:04:11
point so that's why CO2 sublimes from a
00:04:14
solid to a
00:04:16
gas as the temperature
00:04:19
increases now here's a question for you
00:04:23
which phase has a higher density the
00:04:26
liquid phase of CO2 or the solid phase
00:04:30
because for some materials the
00:04:33
liquid has a greater density and for
00:04:36
other materials the solids have a
00:04:38
greater density so how can you tell
00:04:40
based on the phase
00:04:41
diagram well pick a point let's start
00:04:45
with the liquid
00:04:46
phase as you increase the pressure the
00:04:49
density of the material increases
00:04:52
because you're compacting the atoms
00:04:54
together as you squeeze atoms into a
00:04:57
tighter space there's more mass unit
00:04:59
volume and so it has a higher density so
00:05:02
as we increase the pressure notice that
00:05:05
we're going to go from the liquid to the
00:05:06
solid phase so we're going to freeze the
00:05:10
substance and that means that the solid
00:05:13
phase is at a higher pressure than the
00:05:15
liquid phase so in the case of CO2
00:05:19
because
00:05:20
the the melting point curve has a
00:05:22
positive
00:05:24
slope the density of solid CO2 is
00:05:28
greater than that liquid CO2 at higher
00:05:33
pressures now there's another point of
00:05:36
interest and it's called the critical
00:05:40
point the critical point is location
00:05:45
where you beyond the temperature and
00:05:47
pressure of that point you can have a
00:05:49
super critical
00:05:51
fluid a super critical fluid is a fluid
00:05:55
that has properties of a gas and a
00:05:57
liquid it's not exactly a gas and it's
00:06:00
not exactly a liquid but it's in between
00:06:05
the
00:06:07
two like a gas it has a lower density
00:06:11
than a liquid but like a liquid it can
00:06:13
dissolve certain materials like a gas it
00:06:17
can euse through different materials so
00:06:20
it has properties of
00:06:23
both notice that beyond the critical
00:06:27
temperature which is this point
00:06:30
you can no longer liquefy a gas by
00:06:32
increasing the pressure If you increase
00:06:34
the pressure the gas will go directly to
00:06:36
the super critical phase it won't go
00:06:38
into liquid phase a gas can be
00:06:42
liquified when the temperature is below
00:06:45
the critical
00:06:46
temperature if it's above it you're
00:06:48
going to go straight to the super
00:06:49
critical fluid rather than liquefying
00:06:52
the gas at high
00:06:57
pressure now let's go over the phase
00:07:01
diagram for
00:07:10
water so it's a little different for H2O
00:07:13
than it is for
00:07:21
cl2 for one thing notice that the
00:07:24
melting point line has a negative slope
00:07:26
instead of a positive slope As you move
00:07:29
towards the right the line
00:07:33
decreases now this is still going to be
00:07:35
the solid phase this is the liquid and
00:07:36
this is the gas
00:07:38
phase and this
00:07:42
time the pressure of 1 atm is above the
00:07:46
triple
00:07:47
point so because standard pressure is
00:07:49
above the triple point as you increase
00:07:52
the temperature for let's say ice ice is
00:07:55
going to melt into a liquid and as you
00:07:57
continue to increase the temperature the
00:07:59
liquid will vaporize into a
00:08:02
gas so at a pressure of 1
00:08:05
atm you can increase the temperature and
00:08:08
get all three phases of water now if you
00:08:10
decrease the pressure below the triple
00:08:13
point when you heat up the solid it will
00:08:16
Sublime directly into a
00:08:20
gas so sublimation can occur when the
00:08:23
pressure is below the triple
00:08:25
point now let's talk about the density
00:08:27
of water
00:08:30
which phase has a higher
00:08:32
density ice or liquid
00:08:35
water so if we start at this point and
00:08:38
if we increase the pressure if we go
00:08:41
vertically upwards in the phase diagram
00:08:43
notice that we're going to travel from
00:08:45
the solid to the liquid so that means
00:08:47
that the liquid is at a higher pressure
00:08:50
and therefore is more dense uh than the
00:08:53
solid so liquid water has a higher
00:08:56
density than ice that's why ice floats
00:08:59
on
00:09:00
water now this is still the critical
00:09:04
point and above this uh region or in its
00:09:07
region you have the super critical fluid
00:09:12
again so the temperature at the critical
00:09:15
point is called the critical temperature
00:09:18
which is whatever that value is and the
00:09:21
pressure that corresponds to the
00:09:23
critical point is the critical pressure
00:09:31
now what is the difference between the
00:09:33
boiling point of
00:09:34
H2O and the normal boiling point of
00:09:38
H2O the boiling point of water can vary
00:09:42
and it's anywhere along this line
00:09:44
however the normal boiling point is a
00:09:48
specific location on that line the
00:09:50
normal boiling point occurs when the
00:09:52
pressure of the atmosphere is 1
00:09:55
atm so this particular point is the
00:09:58
normal boiling point of
00:10:00
water whereas anywhere along this line
00:10:03
is called the bowling Point curve now
00:10:05
the normal melting point occurs at a
00:10:07
pressure of 1 atm so this is the normal
00:10:10
melting
00:10:12
point and this is called the melting
00:10:15
point
00:10:17
curve so if you hear the word normal
00:10:20
attached to melting point or boiling
00:10:23
point the pressure has to be 1 atm