OB: Intro to phases chemistry
The three states of matter
Solids, liquids, and gases, and
Changing from phase to phase.
You must have a calculator and a
reference table or you won’t learn.
1. Matter comes in three phases, and we know that the matter can
change from phase to phase. We’ll soon learn how and why this happens.
2. There are six phase changes that you need to know always:
Melting/freezing
boiling/condensing
Sublimation/deposition
3. Energy is associated with the phases as well
Gases have the highest energy, solids the lowest.
4. Water is our most common substance, and therefore we need to
always be aware of the temperatures that the phase changes occur
at (at normal pressures).
5. Temperature chart for water at normal pressure.
373 K = 100°C
273 K = 0°C
0 K = absolute zero
5. Temperature chart for water at normal pressure.
Gas phase
373 K = 100°C
Steam condenses, water
vaporizes
Liquid phase
Ice melts, water freezes
SOLID phase
273 K = 0°C
0 K = absolute zero
6. Water is weird, because it’s common to us in all 3 phases.
Most substances are not normally seen in all 3 phases in the normal temperatures
that we live in.
For example:
Kelvin
Temps
Boil temp
gas phase
starts
Freeze
temp
solid below
this temp
Water
Iron
Gold
CO2
373
3023
3080
217
273
1808
1338
195
7. Although most of us wouldn’t
realize this, boiling point is
influenced by the air pressure as
well.
Just like most fish don’t know
they’re wet, we don’t often
realize the effect that the air has
on us or everything else.
8.
Air pressure is measured with these unusual units…
A.
Atmospheres of pressure (atm). One atmosphere is the normal amount of air
above us, so 1.0 atm is considered “normal” air pressure.
B. Millimeters of Mercury (mm Hg) is next. I’ll show you tomorrow how the original
barometers worked, how they measured air pressure. “Normal” was when the
mercury rose up to a height of 760 mm.
C. Kilo-pascals (kPa) is last, and most metric. We’ll use this one the most, and
we’ll get used to the funky names.
D. Pounds per Square Inch (psi) in America. It’s 14.7 psi for standard pressure.
LOOK now at table A on the reference tables. Normal temperature is
both 273 Kelvin or 0°C, and
10.
Normal Pressure is 101.3 kPa, or 1.0 atm. (It’s also 760. mm Hg)
Time for a fun demo of air pressure (or two).
First, notice I have nothing up my sleeves.
I need one of those hats!
11. First, let me tell you that “normal” air pressure is
sometimes still measured in pounds per square inch or psi.
12. Normal pressure is 14.7 psi. I just happen to have a hunk
of steel that’s 1 square inch on the bottom and 14.7 pounds.
Next, let’s notice the force of the air pressure that we never even notice.
Here’s a water glass, like the one in my hand.
The top is about 2 inches across, and with that
Area of a circle formula = πr2
A = (3.14) x (1.25 inch) x (1.25 inch) = 4.91 in2
My water is about a 0.75 pounds, so the
pressure that this water would create if I turned
it upside down would be slight
(about ____________psi)
WATCH! Think!
Water pressure
pushes down,
about ______ psi
Which is stronger?
Air pressure pushes up (14.7 psi)
15.
Air pressure conversions, using the “normal” air pressure equalities
101.3 kPa = 760. mm Hg = 1.0 atm = 14.7 psi
Let’s convert higher than normal air pressure of
145 kPa into atmospheres.
15.
Air pressure conversions, using the “normal” air pressure equalities
101.3 kPa = 760. mm Hg = 1.0 atm = 14.7 psi
Let’s convert higher than normal air pressure of 145 kPa into atmospheres.
145 kPa
1
X 1.0 atm
101.3 kPa
= 1.43 atm
16.
The pressure in a balloon is 905 mm Hg.
What’s that in kPa (kilopascals)?
16. The pressure in a balloon is 905 mm Hg,
what’s that in kilopascals?
905 mm Hg X 101.3 kPa = 121 kPa
760. mm Hg
1
17. As you climb up Mt. Everest (which is
totally unsafe and also dangerous) the air
pressure drops from normal to about
31.0 kPa. What is that in atmospheres?
17. As you climb up Mt. Everest (which is
totally unsafe and also dangerous) the air
pressure drops from normal to about
31.0 kPa. What is that in atmospheres?
31.0 kPa
1
X
1 atm
101.3 kPa
=
= 0.306 atm
3 SF
18. The air pressure in a scuba tank
is in the range of 224 atm.
Convert that into kilo-Pascals.
18. The air pressure in a scuba tank
is in the range of 224 atm.
Convert that into kilo-Pascals.
224 atm
1
X
101.3 kPa
1 atm
=
= 22,691 kPa
= 22,700 kPa
3 SF
Phase class #2
OB: Describing gases with the kinetic
molecular theory of gases, detailing
how barometers work, and then, lots of
pressure unit conversion math
You
Your dog:
Pressure Unit
Conversion Math
AKA: PUC
This theory explains how gases “work”. How they
exist as gases, how they stay gases, how the
particles of gas act (atoms or molecules),
and how we understand gases in our minds.
Depending how you count the concepts, there are
seven points to ponder…
19. The kinetic molecular theory of gases states that gases
A. Are made up of small particles such as atoms or molecules
B. And that these particles will act as if they are small, hard
spheres. They aren’t really, they do have shapes, and
are not spheres, but they act as if this is true.
19. The kinetic molecular theory of gases states that gases
A. Are made up of small particles such as atoms or molecules
B. And that these particles will act as if they are small, hard spheres. They aren’t
really, they do have shapes, and are not spheres, but they act as if this is true.
C. They have no attraction for or any repulsion for any
other gas particles. This is not true either, but the
attraction and repulsion they have for one another
is small, and unless crazy cold, no real effect on
gases.
D. The particles move very fast, and only in straight
lines. It’s very geometric, no spiraling particles.
19. The kinetic molecular theory of gases states that gases
E. All collisions are elastic: when the gas particles hit each
other all of their energy is transferred, none is lost.
This is not true, but the loss of energy is small, and the
addition of energy all the time from the Sun, and the Earth
more than makes up for it. Gases do stay gases usually.
F. Collisions result in pressures being exerted.
The more collisions the higher the pressure.
The stronger the collisions, the higher the gas pressure too.
19. The kinetic molecular theory of gases states that gases
G. Particles are separated by vast distances from each other
relative to the size of the particles. Gases are mostly
empty space, and particle size is insignificant.
The particles do take up some space, but it’s tiny.
In theory, the particles act as if they take up no space at all,
but that’s silly.
20. Gas pressure was originally measured in
pounds per square inch because a bunch of smart
guys, who came from Europe, where they used
pounds for measuring, and who happened to invent
the barometer, decided things.
So a bunch of these science guys go on a long round the world road trip, with a
barometer (so they could say they were working!), and they measured how high up
the mercury went near the oceans, up the mountains, in the hills, in cities, towns,
caves, etc.
They decided amongst themselves what “normal” was. The decision was that
When the mercury rose up to 760. mm in height in the vacuum tube, the air
pushing it that much was “normal” pressure.
The rest is just math conversions,
different instruments, and more math.
Easy but we’ll practice some now.
21. Evangelista Torricelli, circa
1640, father of the Torricelli Tube, or
the early mercury air barometer.
(1 Torr is about 1 mm Hg)
22.
Today it’s a higher pressure day (cold air is denser than warm),
so the pressure outside is about 825 mm Hg. Convert that to
atmospheres and then to kilopascals.
22.
Today it’s a higher pressure day (cold air is denser than warm),
so the pressure outside is about 825 mm Hg. Convert that to
atmospheres and then to kilopascals.
825 mm Hg
1
825 mm Hg
1
X
X
1.0 atm
760. mm Hg
= 1.09 atm
101.3 kPa
760. mm Hg
= 110. kPa
23.
In Boulder, Colorado, where my mean sister in law Donna lives, the air
pressure is notably lower than Vestal. That’s because she’s so high in the
mountains, there is less air pressing on them than at lower altitudes like here.
Air pressure in Boulder the other day was just 644 mm Hg. You’d be
light headed probably. Convert that to atm and to kPa.
23.
In Boulder, Colorado, where my mean sister in law Donna lives, the air
pressure is notably lower than Vestal. That’s because she’s so high in the
mountains, there is less air pressing on them than at lower altitudes like here.
Air pressure in Boulder the other day was just 644 mm Hg. You’d be
light headed probably. Convert that to atm and to kPa.
644 mm Hg
1
X
644 mm Hg X
1
101.3 kPa
760. mm Hg
1.0 atm
760. mm Hg
= 85.8 kPa
= 0.847 atm
24. Convert 40.0 kPa into mm Hg and then into atm.
24. Convert 40.0 kPa into mm Hg and then into atm.
40.0 kPa
1
40.0 kPa
1
X
760 mm Hg
101.3 kPa
X
1.0 atm
101.3 kPa
= 300. mm Hg
= 0.395 atm
25. Last set today.
Convert 2.55 atm into kilopascals and
then into mm Hg
25. Last set today.
Convert 2.55 atm into kilopascals and
then into mm Hg
2.55 atm X 101.3 kPa
1
1.0 atm
2.55 atm X 760 mm Hg
1
1.0 atm
= 258 kPa
= 1938 kPa
1940 kPa
with 3SF
Phase Class #3 – Liquids
get a calculator + reference table now
Review temperature and
pressure conversions,
Table H and
vapor pressure.
26. Convert these 4 now…
A. 120⁰C into Kelvin
B. 327 Kelvin to centigrade
C. 0.556 atm to mm Hg
D. 4.57 atm to kPa
26. Convert
120⁰C into Kelvin
327 Kelvin to centigrade
0.556 atm to mm Hg
4.57 atm to kPa
K = C + 273
K = 120 + 273 = 393 Kelvin
K = C + 273
327 K = C + 273
327 K = 54⁰C
0.556 atm
1
X
760 mm Hg
1.0 atm
4.57 atm X 101.3 kPa
1
1.0 atm
=
=
423 mm Hg
463 kPa
27. Liquids are substances with particles
sliding on each other, attached loosely
by inter particle attractions.
The particles do not have enough kinetic
energy (motion) to shake apart into a gas, nor
so little energy that they would lock together
into a solid.
28. When liquids get enough energy they reach the boiling point.
At the boiling point ALL molecules of a liquid have enough energy
to go into the gas phase. This is called vaporization.
29. Vaporization is evaporation too, which is when few particles of
a liquid get enough energy by bouncing around to escape to the
gas phase.
30. Evaporation happens to every liquid at every temperature.
32. The hotter liquids are, the more evaporation can occur since more particles
get enough energy to leap to a gas.
See the water evaporating
from the lake?
On every day, no matter
what the temperature, all
day long, at least some
water evaporates.
Phase change from liquid to gas…
33. Evaporation is when some water molecules (any liquid) escape because
individually they get enough kinetic energy to jump into the air.
Boiling is when the entire liquid has enough kinetic energy to change phase.
34. When kinetic energy
exceeds the forces of
attraction, liquids become gases.
This is an OPEN SYSTEM, the
beaker will eventually empty.
LIQUID
35. If this liquid is boiling it’s
quicker, if it’s cool, then the
vaporization process is slower.
In Vestal we have a normal air
pressure, our altitude is about 1000
feet above sea level.
In Boulder, they’re nearly 5,400
feet above sea level, so their air
pressure is markedly lower.
If the pressure is normal here, it’s
about 85% lower there.
Vestal 1.0 atm
Boulder 0.85 atm.
What temperature will that water
boil in Boulder?
36. How do we figure this out?
Donna lives high up in the
Rockies, in Boulder Colorado.
She does like to cook potions,
but things with her are not like
they are with you here.
For example, she never shops
at a mall.
37.
Vestal
101.3 kPa
70°C
Vestal
101.3 kPa
100°C
Boulder
85.0 kPa
~97°C
Air Pressure
Air Pressure
Air Pressure
water
water
water
Water does not boil.
Water does boil.
It can’t over come the
attraction and downward
air pressure
Evaporation happens
It can overcome the
attraction and downward
air pressure
Evaporation happens
Water boils at a lower
temperature!
There is lower air pressure
holding it down
in the pot!
38. Liquids (even water) boil when all the particles have enough energy to
overcome the internal attraction that they have for themselves, and
enough energy to overcome the air pressure pushing down upon the surface.
39. Boiling point is not JUST temperature driven, it’s controlled by the
temperature and the pressure together.
40. High pressures will increase the energy (temperature) required to boil
any liquid. Lower pressures will decrease the energy needed to boil a liquid.
41. The internal attraction of the particles is a constant for each particular
liquid. This internal attraction is measured by VAPOR PRESSURE.
42. In a closed system, at a steady temperature a dynamic equilibrium
is reached. This is when the evaporation rate equals the condensation
rate. This is only possible in a closed system.
Corked
top
Condensation
(down arrows)
Evaporation (up arrows)
WATER
In a closed system, at a steady temperature a dynamic equilibrium is
reached. This is when the evaporation rate equals the condensation
rate. This is only possible in a closed system.
Corked
top
43.
If the system is heated,
more evaporation occurs,
until a new
dynamic equilibrium
is reached.
If it’s cooled,
less evaporation will occur,
until a new dynamic equilibrium
is reached.
WATER
Condensation
(down arrows)
Evaporation (up arrows)
44.
This space above the
water contains air, and has
air pressure that matches
the air pressure outside
the glass. The evaporation
causes more particles of
gas to move into that space,
increasing the pressure.
This extra pressure is
called
VAPOR PRESSURE.
Corked
top
WATER
Condensation
(down arrows)
Evaporation (up arrows)
45.
The vapor pressure of water (part of table H)
101.3 kPa
Pressure
kPa
0
50
100
temperature, Centigrade degrees
The vapor pressure of water (part of table H)
46. Big black dot indicates the
“normal boiling point”, which is
the BP at normal pressure.
101.3 kPa
47. The curved
line indicates ALL
of the boiling points
of water, at all
different
pressures.
Pressure
kPa
0
50
100
temperature, Centigrade degrees
The vapor pressure of water (part of table H)
48. H2O at these
pressures and
temperatures is a
101.3 kPa
LIQUID
49. H2O at
these pressures
and temperatures
is a GAS
Pressure
kPa
0
50
100
temperature, Centigrade degrees
50. Table H is the vapor pressure of 4 different compounds, water included.
Only look at one curve, or one liquid, at any time. Behind the curve is liquid,
in front of the curve it’s a gas.
Phase Class #4
Understanding Table H and
Vapor Pressure
Take out your reference tables now
51. In a closed system, at a steady temperature a dynamic equilibrium
is reached. This is when the evaporation rate equals the condensation
rate. This is only possible in a closed system.
Corked
top
Air pressure outside bottle is
about 101.3 Pa, same inside
to start.
Condensation
(down arrows)
WATER
Evaporation (up arrows)
52.
If the close system is heated, more evaporation occurs,
until a new dynamic equilibrium is reached.
If it’s cooled, less evaporation will occur, until a new dynamic equilibrium is reached.
Corked
top
Air pressure outside still about 101.3 kPa,
inside the pressure is increasing.
WATER
Condensation
(down arrows)
Evaporation (up arrows)
53.
The extra pressure inside that bottle is called the vapor pressure.
It’s added to the existing air pressure present from the start.
Corked
top
Air pressure outside still about 101.3 kPa,
inside the pressure is increasing.
WATER
Condensation
(down arrows)
Evaporation (up arrows)
54.
Table H is the vapor pressure of 4 different compounds, water included. Only look at
one curve, or one liquid, at any time. Behind the curve is liquid. In front is a gas.
Table H is the vapor pressure of 4 different compounds, water included. Only look at one
curve, or one liquid, at any time. Behind the curve is liquid. In front is a gas.
Let’s Just Do This Slide, no notes…
Let’s talk ONLY
about water…
At each point,
what phase is
the water in?
1.
2
1
4
2.
3.
3
4.
Table H is the vapor pressure of 4 different compounds, water included. Only look at one
curve, or one liquid, at any time. Behind the curve is liquid. In front is a gas.
Let’s talk ONLY
about water…
At each point,
what phase is
the water in?
1. liquid
2
1
4
2. liquid
3. liquid
3
4. gas
55.
At each point,
what is the vapor
pressure of water?
101.3 kPa + 40⁰C
75 kPa + 95⁰C
150 kPa + 110⁰C
20 kPa + 65⁰C
55. At each point,
what is the vapor
pressure of water?
101.3 kPa + 40⁰C
LIQUID
75 kPa + 95⁰C
GAS
150 kPa + 110⁰C
LIQUID
20 kPa + 65⁰C
GAS
JUST DO
THESE TOO
At these points
A, B, and C
What phase is
water?
A
C
B
What phase is
ethanoic acid?
What phase is
ethanol?
What phase is
propanone?
At points
A, B, and C
What
phase is
water?
A
C
B
A liquid
B gas
C liquid
At points
A, B, and C
A
C
B
What
phase is
ethanoic
acid?
A liquid
B liquid
C liquid
At points
A, B, and C
What
phase is
ethanol?
A
C
B
A liquid
B gas
C gas
At points
A, B, and C
What phase
is
propanone?
A
C
B
A gas
B gas
C gas
56.
How much
extra
pressure is
added to a
sealed flask
containing
water at
50⁰C?
56A.
(what’s the
vapor pressure
of water at
50⁰C?)
Phase Class #5
OB: Practice phase concepts:
cooling and heating curves,
phase diagrams, pressure conversions,
table H problems.
Take out reference tables.
57.
Draw the Cooling curve for cobalt. 58. On the same graph, draw the heating curve
for cadmium. Titles, axis labels and scales, be big. Write BP + FP for both.
3200
2400
Temp
Kelvin
1600
800
Energy added (or removed) at constant rate over time
Draw the heating curve for cobalt. On the same graph, draw the cooling curve for
cadmium. Titles, axis labels and scales, be big.
3200
Cadmium
BP: 1040 K
FP: 594 K
2400
Temp
Kelvin
1600
Cobalt
BP: 3200 K
FP: 1768 K
800
Energy added (or removed) at constant rate over time
59.
Why are the flat lines different lengths on every heating curve (and every cooling curve)?
60. BC represents the
melting of ice. It takes for
water, 334 Joules of energy
to melt one gram of ice from
solid to liquid without
increasing the temperature.
It’s called the heat of fusion
For water: HF = 334 J/gram
61. DE represents the
boiling of water into steam.
It takes for water, 2260
Joules of energy to vaporize
one gram of water to steam
without increasing the
temperature.
It’s called the heat of
vaporization
For water: HV= 2260 J/gram
62. The phase change from liquid
to gas is MUCH more energetic
than melting solid to liquid.
For water, it’s ~ 7X more!
63. A phase diagram shows a substance’s range of phases through temperature + pressures.
Here is the phase diagram for water.
64. Special Points on
this graph:
Tm: normal melting point
Tb: normal boiling point
TP: triple point
CP: critical point
Imagine you have two beakers of liquid, one has 500. mL ethanol alcohol and the other
has 500. mL of propanone. They are sitting on the desk in front of you. Put a cork into
each top.
AIR PRESSURE
101.3 kPa
Start pressure
inside flasks
the same
Warm up the
room to 25⁰C
65.
What is
pressure
inside each
flask?
Imagine you have two beakers of liquid, one has 500. mL ethanol alcohol and the other
has 500. mL of propanone. They are sitting on the desk in front of you. Put a cork into
each top.
AIR PRESSURE
101.3 kPa
Start pressure
inside flasks
the same
25⁰C
Vapor Pressure ethanol
@ 25⁰C is about
8 kPa
Vapor pressure propanone
@ 25⁰C is about
31 kPa
66. What if we heat it up to 65⁰C next???
Imagine you have two beakers of liquid, one has 500. mL ethanol alcohol and the other
has 500. mL of propanone. They are sitting on the desk in front of you. Put a cork into
each top.
AIR PRESSURE
101.3 kPa
Start pressure
inside flasks
the same
65⁰C
Vapor Pressure ethanol
@ 65⁰C is about
60 kPa
Vapor pressure propanone
@ 65⁰C is about
135 kPa
KABOOM!
67. Properties of SOLIDS, LIQUIDS, and GASES Compared
SOLIDS
Particles are strongly attracted to each other, other than some vibration there is
nearly no movement of the atoms or molecules, they have a rigid or lattice
arrangement of the particles, they keep their shapes and volumes, they do not
take the shape of their containers. Solids cannot be compressed very much
because the particles are very close together.
Because of this most solids have a high density compared to their liquids or
gases. When energy or heat is added, the particles will vibrate more, which often
makes solids expand when heated. Particles in solids have the lowest kinetic
energy. Give solids enough energy (at the proper pressure) and they will vibrate
so much that they break apart and turn into ....
LIQUIDS
Particles have some attraction to each other but not enough to make
them stuck. Liquids flow over themselves, the particles are in
constant random motion. Liquids do not have a definite shape which
means they take the shape of the container you put them in.
If you spill liquids, the force of gravity spreads them out quite well.
The hotter liquids get when you add energy, the faster the particles
move, and liquids too expand slightly when heated. Liquids are dense
as well, but usually not as dense as solids are. Heat a liquid enough,
the particles move so much that they turn into...
GASES
There is virtually no attractive or repulsive force between the
particles. The particles move in straight lines and very fast. They
collide with other particles all of the time. These collisions will cause
gas (or air) pressure. Gases take the shape of the container that you
put them in. Any amount of a gas will fill any container that you put
it in.
The collisions are considered to be elastic, meaning there is no loss
of kinetic energy due to the collisions. Heated gases make the
particles move faster and have more collisions, causing expansion if
possible, or greater pressures if contained in a definite volume. Gas
Particles have the highest kinetic energy. Gases have very low
density.
Gas Pressure is measured with different pressure units, all on table A. Let’s add mm Hg
now to the reference tables now.
1.0 atm = 760. mm Hg = 101.3 kPa = 14.7 psi
68. Today’s pressure is exactly 1.14 atm.
Convert that to mm Hg, and kPa right now…
This slide left
intentionally
blank, you
know why…
68.
1.14 atm X
1
760. Mm Hg = 866 mm Hg
1.0 atm
1.14 atm X 101.3 kPa
1
1.0 atm
= 115 kPa
(3 SF)
(3 SF)
69. At any temperature, say 65°C,
ethanonic acid has the
lowest vapor pressure,
propanone the highest. WHY???
Each liquid, these 4 included,
at any one temperature will
evaporate to a certain
degree.
How much this happens is
connected first to the
temperature, and then, to
how strong the intermolecular attractions the
molecules have for each
other.
At 65°C
Propanone has the lowest
intermolecular attraction
and therefore the highest
vapor pressure.
Ethanoic acid has strong
intermolecular attraction,
so low vapor pressure.
70.
Put 2 notes onto your reference tables now.
Propanone has the highest vapor pressure of these four liquids, at any
temperature, because it has the weakest intermolecular attractions for
itself.
Ethanoic acid has the
lowest vapor pressure of
these four liquids, at
any temperature
because it has the
strongest intermolecular
attractions for itself.
Heating curve for an unknown substance
BP
K
FP
71.
Label points A to F left to right
Show what happens to Temperature
from points BC and DE
Then explain
Potential Energy from BC and DE
(use next slide to draw)
Energy being added at a constant rate over time.
Heating curve for an unknown substance
BP
in
K
FP
Energy being added at a constant rate over time.
Heating curve for an unknown substance
D
BP
F
PE
E
BC there is no change in temperature.
in
K
DE there is no change in temperature.
B
FP
Ergo: Kinetic Energy is steady.
PE
Potential Energy must increase there.
C
A
Energy being added at a constant rate over time.
Heating curve for an unknown substance
D
BP
E
in
Temp
K
KE
FP
B
C
From CD there is an increase in
temperature.
That means Kinetic Energy
Increases too
72.
If kinetic energy is changing,
What does the potential energy do
from C to D?
Energy being added at a constant rate over time.
Heating curve for an unknown substance
D
BP
E
in
Temp
K
KE
FP
B
C
From CD
there is an increase in temperature.
That means Kinetic Energy Increases
too
If kinetic energy is changing,
Potential Energy is steady
Energy being added at a constant rate over time.
73. Kinetic Energy & Temperature are the same thing, sort of.
The greater the KE, the greater the temp.
Lower temp = Lower KE
74.
Temp + Kinetic energy
are like Michael Jackson’s hand & his glove.
What ever one does, so does the other.
75.
The other energy, Potential Energy,
is used when there is no change in
the kinetic energy. It’s for those phase change times.
76. If kinetic energy (temp) is changing, potential energy is steady.
77. In a phase change kinetic energy is steady (so is temp),
then the PE is going up in a heating curve, or
the PE is going down in a cooling curve.