Energy is defined as the ability to
do work.
Work = force x distance
The ability to do work.
 Work - cause a change or move an
object.
 Many types- all can be changed into the
other.
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Potential- stored energy
◦ Position, condition or composition
Kinetic Energy- energy something has
because its moving
Heat- the energy that moves because of a
temperature difference.
Chemical energy- energy released or
absorbed in a chemical change.
Electrical energy - energy of moving
charges
Radiant Energy- energy that can travel
through empty space (light, UV, infrared,
radio)
 Nuclear Energy – Energy from changing the
nucleus of atoms

*All types of energy can be converted into
others.
 If you trace the source far enough back, you will end up
at nuclear energy.
Energy can be neither created or destroyed in
ordinary changes (not nuclear), it can only
change form.
 Discovered by Julius Robert Mayer in 1842
 Now called: The First Law of Thermodynamics
Law of Conservation of Mass - Energy
The total amount of mass and energy in
the universe is constant.
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Some theories are based on supporting
postulates.
A postulate is a statement which is agreed on
by consensus among scientists.
The following are important postulates of the
kinetic molecular theory:
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All matter consists of atoms.
Atoms may join together to form molecules.
Solids usually maintain both their shape and
their volume.
Liquids maintain their volume, but not their
shape.
Gases do not maintain shape or volume. They
will expand to fill a container of any size.
Molecular motion is random.
Molecular motion is greatest in gases, less in
liquids, and least in solids.
Collisions between atoms and molecules
transfers energy between them.
Molecules in motion possess kinetic energy.
Molecules in gases do not exert large forces on
one another, unless they are colliding.
Also see chapter 11 of textbook
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Thermal energy is the average of the
potential and kinetic energies possessed by
atoms and molecules experiencing random
motion.
Heat is transferred by convection,
conduction, or radiation. (review the definitions of these
words)

Heat is the thermal energy transferred from
one object to another due to differences in
temperature. Heat flow from high to low
temperature.
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There is no direct method used to measure
heat. Indirect methods must be used.
Temperature is a measure of the average
kinetic energy of the molecules of a
substance.
 There is a direct relationship between
temperature and avg. kinetic energy!
 Temperature can be measured with a
thermometer.
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One way a thermometer can be calibrated is
by the amount of thermal expansion and
contraction that occurs within a given type of
substance.
Thermometers are limited by the physical
properties of the substance from which they
are made. (i.e., An alcohol thermometer is of
little use above the boiling point of alcohol,
and a mercury thermometer will not be of any
use below the freezing point of mercury.)
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Both scales are based on the freezing
conditions of water, a very common and
available liquid.
Since water freezes and boils at temperatures
that are rather easy to generate (even before
modern refrigeration), it is the most likely
substance on which to base a temperature
scale.
100ºC = 212ºF
0ºC = 32ºF
0ºC
32ºF
100ºC 212ºF
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Zero Fahrenheit was the coldest temperature
that the German-born scientist Gabriel Daniel
Fahrenheit could create with a mixture of ice
and ordinary salt.
He invented the mercury thermometer and
introduced it and his scale in 1714 in
Holland, where he lived most of his life.

Anders Celsius, a Swedish astronomer,
introduced his scale is 1742.
 For it, he used the freezing point of water as zero
and the boiling point as 100.
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For a long time, the Celsius scale was called
"centigrade."
 The Greek prefix "centi" means one-hundredth and
each degree Celsius is one-hundredth of the way
between the temperatures of freezing and boiling
for water.

The Celsius temperature scale is part of the
"metric system" of measurement (SI) and is
used throughout the world, though not yet
embraced by the American public.
How much it
changes
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
0ºC 100ºC
212ºF 32ºF
How much it
changes
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
1ºC = (180/100)ºF
1ºC = 9/5ºF
0ºC 100ºC
212ºF 32ºF
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Scientists use a third scale, called the "absolute" or
Kelvin scale.
This scale was invented by William Thomson, Lord
Kelvin, a British scientist who made important
discoveries about heat in the 1800's.
Scientists have determined that the coldest it can
get (theoretically) is minus 273.15 degrees Celsius.
This temperature has never actually been reached,
though scientists have come close. The value,
minus 273.15 degrees Celsius, is called "absolute
zero".
At this temperature scientists believe that
molecular motion would stop. You can't get any
colder than that.
The Kelvin scale uses this number as zero. To get
other temperatures in the Kelvin scale, you add
273 degrees to the Celsius temperature.
The important idea is that temperature is really a
measure
of something, the average motion (kinetic energy,
KE) of the molecules.
KE = ½ mv2
Does 0°C really mean 0 KE? nope... it simply means
the
freezing point of water, a convenient standard.

We have to cool things down to –273.15°C before
we reach
0 KE. This is called 0 Kelvin (0 K, note: NO ° symbol.)

For phenomena that are proportional to the KE of
the
particles (pressure of a gas, etc.) you must use
temperatures in K.

K
= °C + 273
 °C
= K – 273
 °F
= 9/5 °C + 32
 °C
= 5/9 (°F – 32)
Note: In Kelvin
notation, the degree
sign is omitted: 283K
Celsius to Fahrenheit:
*A mental shortcut for a rough estimate:
·
Double the temperature given in Celsius
·
Add 30 to the result to find the approximate temperature
in Fahrenheit.
Celsius Temperature to Fahrenheit
More Celsius to Fahrenheit
Fahrenheit to Celsius
More Fahrenheit to Celsius
Fahrenheit to Celsius:
*A mental shortcut for a rough estimate:
·Subtract 30 from the temperature given in Fahrenheit
· Take half of the result to find the approximate
temperature in Celsius.
Celsius Temperature to Fahrenheit
More Celsius to Fahrenheit
Fahrenheit to Celsius
More Fahrenheit to Celsius
Energy is measured in many ways.
BTU
 One of the basic measuring blocks is called
a Btu. This stands for British thermal unit
and was invented by the English.
 Btu is the amount of heat energy it takes to
raise the temperature of one pound of
water by one degree Fahrenheit, at sea
level.
◦ One Btu equals about one blue-tip kitchen match.
◦ One thousand Btus roughly equals: One average candy bar
or 4/5 of a peanut butter and jelly sandwich.
◦ It takes about 2,000 Btus to make a pot of coffee.
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A calorie is a unit of measurement for energy.
Calorie is a French word derived from the Latin
word: calor (heat).
Modern definitions for calorie fall into two classes:
 The small calorie or gram calorie approximates the
energy needed to increase the temperature of 1
gram of water by 1 °C. This is about 4.184 joules.
 The large calorie or kilogram calorie approximates
the energy needed to increase the temperature of 1
kg of water by 1 °C. This is about 4.184 kJ, and
exactly 1000 small calories.
 1 cal = 4.184 J
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Energy also can be measured in joules.
(Joules sounds exactly like the word jewels,
as in diamonds and emeralds.)
A thousand joules is equal to a British
thermal unit.
1,000 joules = 1 Btu
So, it would take 2 million joules to make a
pot of coffee.
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The term "joule" is named
after an English scientist
James Prescott Joule who
lived from 1818 to 1889.
He discovered that heat is a
type of energy.
One joule is the amount of
energy needed to lift
something weighing one
pound to a height of nine
inches.
Around the world, scientists
measure energy in j.
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Like in the metric system, you can have
kilojoules -- "kilo" means 1,000.
1,000 joules = 1 kilojoule = 1 Btu
1 cal = 4.184 J
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Temperature is a measure of the Average
kinetic energy of the molecules of a
substance.
Higher temperature faster molecules.
At absolute zero (0 K) all molecular motion
would stop.
High temp.
%
o
f
M
o
l
e
c
u
l
e
s
Low temp.
Kinetic Energy
%
o
f
M
o
l
e
c
u
l
e
s
High temp.
Low temp.
Average
kinetic
energies are
temperatures
Kinetic Energy
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The average kinetic energy is directly
proportional to the temperature in Kelvin
If you double the temperature (in Kelvin)
you double the average kinetic energy.
If you change the temperature from 300 K
to 600 K the kinetic energy doubles.
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If you change the temperature from 300ºC to
600ºC the Kinetic energy doesn’t double.
873 K is not twice 573 K
Melting
Solid
Vaporization
Liquid
Freezing
Gas
Condensation
endothermic
Sublimation
Melting
Vaporization
Solid
Liquid
Freezing
Gas
Condensation
Deposition
exothermic
Heating Curve for Water
120
Steam
Water and
Steam
100
80
60
Water
40
20
0
Ice
Water
and Ice
-20
0
40
120
220
760
800
Heating Curve for Water
120
Water and
Steam
100
gas
Steam
80
liquid
60
Water
40
20
0
Ice
Solid
-20
0
40
Slope =
Specific Heat
Water
and Ice
120
220
760
800
Heating Curve for Water
120
Steam
Water and
Steam
100
80
60
Water
40
20
Both Solid
Water
and Ice
Iceand liquid
0
-20
0
40
120
220
760
800
Heating Curve for Water
120
BothWater
liquid
and
and Steam
gas
100
80
Steam
60
Water
40
20
0
Ice
Water
and Ice
-20
0
40
120
220
760
800
Heating Curve for Water
120
Heat
ofand
Water
Steam
Vaporization
100
Steam
80
60
Water
40
20
0
Ice
Water
and Ice
-20
0
40
120
220
760
800
Heating Curve for Water
120
Steam
Water and
Steam
100
80
60
Water
40
20
Heat ofWater
Ice Fusionand Ice
0
-20
0
40
120
220
760
800
Heating Curve for Water
120
Steam
Water and
Steam
100
80
60
Water
40
Plateau = phase equilibrium
20
0
Ice
Water
and Ice
-20
0
40
120
220
760
800
43
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The specific heat capacity (C) determines
the rate at which heat will be absorbed.
Even though mass is present in the
formula it is an intensive property like
density and is unique for each substance.
The specific heat capacity for water is
4.18J/g
The quantity of heat absorbed (Q) can be
calculated by: Q=mCT
m=mass T=change in temperature
J Deutsch 2003
44
Heat capacity is an extensive property,
meaning it depends on the mass of the
object.
Ex: 1000g of water can hold more heat than
10 g of water.
Q means heat energy lost or gained.
Law of Conservation of Mass-Energy
m= mass of substance; Cp= specific heat
capacity; T = change in temperature
Qlost = Qgained
Three equations:
 Q= mass x Cp x T
 Q= Hf x mass
 Q= Hv x mass
Heating Curve for Water
120
Steam
Water and
Steam
100
80
60
Water
40
20
0
Ice
Water
and Ice
-20
0
40
120
220
760
800
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Heat of fusion energy required to change one
gram of a substance from solid to liquid.
(endothermic rxn)
Heat of solidification energy released when
one gram of a substance changes from liquid
to solid. (exothermic rxn)
For water 80 cal/g or 334 J/g
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Heat of vaporization energy required to
change one gram of a substance from liquid
to gas. (endothermic rxn)
Heat of condensation energy released when
one gram of a substance changes from gas to
liquid. (exothermic rxn)
For water 540 cal/g or 2260 J/g
Three equations:
Q= mass x Cp x T
(used at slopes)
Q= Hf x mass
Q= Hv x mass
(used at s/l equilibria)
(used at l/g equilibria)
Heating Curve for Water
120
Steam
Water and
Steam
100
80
60
Water
40
20
0
Ice
Water
and Ice
-20
0
40
120
220
760
800
As ice melts at standard pressure, its temperature remains at 0°C until
it has completely melted. Its potential energy
(1) decreases
(2) increases
(3) remains the same
52
A sample of water is heated from a liquid at 40°C to a gas at 110°C. The
graph of the heating curve is shown in your answer booklet.
a On the heating curve diagram provided in your answer booklet, label
each of the following regions:
Liquid, only
Gas, only
Phase change
Gas Only
Phase change
Liquid Only
53
b For section QR of the graph, state what is happening to the water
molecules as heat is added.
They move faster, their
temperature increases.
c For section RS of the graph, state what is happening to the water
molecules as heat is added.
Their intermolecular
bonds are breaking, their
potential energy is
increasing.
54
What is the melting point of this substance?
(1) 30°C (3) 90°C
(2) 55°C
(4) 120°C
55

Melting (fusion) or freezing
(solidification)
◦ Q=mHf where Hf is the heat of fusion
(for water: 333.6 J/g)

Boiling (vaporization) or condensing
◦ Q=mHv where Hv is the heat of vaporization
(for water: 2259 J/g)
Hf and Hv are given to Table B – m is the
mass
56
In which equation does the term “heat” represent heat of fusion?
(1) NaCl(s) + heat  NaCl(l)
(2) NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(l)+ heat
(3) H2O(l)+ heat  H2O(g)
(4) H2O(l)+ HCl(g) H3O+(aq) + Cl –(aq) + heat
Fusion refers to melting.
J Deutsch 2003
57
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The temperature at which a liquid and a solid
are in equilibrium
The melting point for ice is 0ºC
The melting point of a substance is the same
as its freezing point
J Deutsch 2003
58
The solid and liquid phases of water can exist in a state of equilibrium at
1 atmosphere of pressure and a temperature of
(1) 0°C
(2) 100°C
(3) 273°C
(4) 373°C
J Deutsch 2003
59
The total heat = the sum of all the heats you
have to use
 Go in order
Heat
Ice
Below
0 C
+
Melt
Ice
At
0 C
+
Heat
Water
+
0 C -
100 C
Boil
Water
+
At
100 C
Heat
Steam
Above
100 C
Heating Curve for Water
120
Steam
Water and
Q Steam
+
100
80
Q
+
60
Q
40
Water
+
20
0
Q+
Ice
-20
0
40
Q
Water
and Ice
120
220
760
800
Heating Curve for Water
Q=m x Cp
x ∆T
Steam
Water and
Q= Hv Steam
xm
120
100
80
Q=m x Cp x ∆T
60
Water
40
20
Q= Water
Hf x m
and Ice
Ice
Q=m
x Cp
x ∆T
0
-20
0
40
120
220
760
800