Download Section 12.4 Phase Changes (cont.)

Section 12.4 Phase Changes
• Explain how the addition
and removal of energy
can cause a phase
change.
• Interpret a phase
diagram.
phase change: a
change from one state
of matter to another
Section 12.4 Phase Changes (cont.)
melting point
freezing point
vaporization
condensation
evaporation
deposition
vapor pressure
phase diagram
boiling point
triple point
Matter changes phase when energy is
added or removed.
12.4 Phase Changes That Require Energy
http://www.youtube.com/watch?v=2E4uK6zoJmo
•Watch the video and copy his diagram (see Colson’s white board)
p. 425
Phase Changes That Require Energy (cont.)
• The melting point of a crystalline solid is the
temperature at which the forces holding the
crystal lattice together are broken and it
becomes a liquid.
• Molecules are freer to move as solid
liquid gas
Phase Changes That Require Energy (cont.)
p. 426
Once over the hump
of KE, substance can
vaporize
Phase Changes That Require Energy (cont.)
• Vaporization is the process by which a
liquid changes to a gas or vapor.
• Evaporation is vaporization only at the
surface of a liquid.
Phase Changes That Require Energy (cont.)
• In a closed container, the pressure exerted
by a vapor over a liquid is called vapor
pressure.
•In closed
container,
water
leaving/
entering
is equal
Phase Changes That Require Energy (cont.)
• The boiling point is the temperature at
which the vapor pressure of a liquid equals
the atmospheric pressure.
Phase Changes That Require Energy (cont.)
• Sublimation is the
process by which a solid
changes into a gas
without becoming a
liquid.
Phase Changes That Release Energy
• As heat flows from water to the
surroundings, the particles lose energy.
• The freezing point is the temperature at
which a liquid is converted into a crystalline
solid.
• FYI: Melting point and freezing point are the
same points, just opposite direction of phase
change
Phase Changes That Release Energy (cont.)
• As energy
flows from
water vapor,
the velocity
decreases.
•Deposition is the process
by which a gas or vapor
changes directly to a solid,
and is the reverse of
sublimation.
• The process by
which a gas or
vapor becomes
a liquid is
called
condensation.
Phase Diagrams
• A phase diagram:
• graph of pressure versus temperature
• shows in which phase a substance will
exist under different conditions of
pressure and temperature.
Phase Diagrams (cont.)
• The triple point is the point on a phase
diagram that represents the temperature
and pressure at which all three phases of a
substance can coexist.
p. 429
What do the Lines of a Phase Diagram tell me?
1. Short Yellow Curve: Shows T & P conditions
under which solid water & water vapor can
co-exist.
2. Long Blue Curve: shows T & P conditions
under which liquid water & water vapor can
co-exist
3. Red Curve: shows the T & P conditions
under which solid water & liquid water can
co-exist
What do the Lines of a Phase Diagram tell me?
A. Triple Point: defined on earlier slide
B. Critical Point: this point indicates the
critical T & P above which water cannot
exist as a liquid
Phase Diagrams (cont.)
• The phase diagram for different
substances are different from water.
p. 430
Bright Storm
Video
•http://www.youtube.com/watch?v=e1mo-BVIvcA
Section 12.4 Assessment
The addition of energy to water molecules
will cause them to ____.
A. freeze
B. change to water vapor
D
A
0%
C
D. move closer together
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. form a crystal lattice
Section 12.4 Assessment
The transfer of energy from one object to
another at a lower temperature is ____.
A. heat
B. degrees
D
A
0%
C
D. electricity
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. conductivity
Energy and Chemical Change
Section 15.1 Energy
Section 15.2 Heat
Section 15.3 Thermochemical
Equations
Section 15.4 Calculating Enthalpy
Change
Section 15.5 Reaction Spontaneity
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the corresponding slides.
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Section 15.1 Energy
• Define energy.
• Distinguish between potential and kinetic energy.
• Relate chemical potential energy to the heat lost or
gained in chemical reactions.
• Calculate the amount of heat absorbed or released by
a substance as its temperature changes.
temperature: a measure of the average kinetic
energy of the particles in a sample of matter
Section 15.1 Energy (cont.)
energy
law of conservation of energy
chemical potential energy
heat
calorie
joule
specific heat
Energy can change form and flow, but
it is always conserved.
The Nature of Energy
• Energy is the ability to do work or produce
heat.
• Two forms of energy exist, potential and
kinetic.
• Potential energy is due
to composition or position.
• Kinetic energy is energy
of motion.
The Nature of Energy (cont.)
• The law of conservation of energy states
that in any chemical reaction or physical
process, energy can be converted from
one form to another, but it is neither
created nor destroyed—also known as the
first law of thermodynamics.
The Nature of Energy (cont.)
• Chemical potential energy is energy
stored in a substance because of its
composition.
• Chemical potential energy is important in
chemical reactions.
• Heat is energy that is in the process of
flowing from a warmer object to a cooler
object.
• q is used to symbolize heat/energy.
Measuring Heat
• A calorie is defined as the amount of
energy required to raise the temperature of
one gram of water one degree Celsius.
• Food is measured in Calories, or 1000
calories (kilocalorie).
• A joule is the SI unit of heat and energy,
equivalent to 0.2390 calories.
Measuring Heat (cont.)
Specific Heat
• The specific heat of any
substance is the amount of
heat required to raise one gram
of that substance one degree
Celsius.
• Some objects require more
heat than others to raise their
temperature.
Specific Heat (cont.)
• Calculating heat absorbed and released
• q = c × m × ∆T
• q = heat absorbed or released
• c = specific heat of substance (see
Table 15.2)
• m = mass of substance in grams
• ∆T = change in temperature in Celsius
Click here for tutorial video
Section 15.1 Assessment
The heat required to raise one gram of
a substance by one degree Celsius is
called ____.
A. joule
A
0%
D
D. energy
C
C. specific heat
A. A
B. B
C. C
0%
0%
0%
D. D
B
B. calorie
Section 15.1 Assessment
Which of the following is an example of
chemical potential energy?
A. the moon orbiting Earth
B. a car battery
D
A
0%
C
D. a roller coaster at the top of a hill
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. a compressed spring