Chapter 3
Matter and
Energy
Homework
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Assigned Problems (odd numbers only)
“Questions and Problems” 3.1 to 3.41
(begins on page 61)
“Additional Questions and Problems”
3.49 to 3.69 (page 87-88)
“Challenge Questions” 3.71 and 3.75,
(page 88)
Matter
Matter is any material that has mass and
occupies space
„ Matter is made up of small particles
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Atoms
„ Molecules
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Includes all things (living and nonliving)
such as plants, soil, and rocks
„ Any material we use such as water,
wood, clothing, etc.
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Matter and Energy
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Chemistry is the study of matter
„ The properties of different types of matter
„ The way matter behaves when influenced by
other matter and/or energy
Nearly all changes that matter undergoes
involves the release or absorption of energy
Energy is the part of the universe that has the
ability to do work
Classification of Matter
Matter
Pure Substance
Mixture
Pure Substance
Matter that has a definite and
constant composition
„ Always contains the same
substance, never varies
„ Either elements or compounds,
all of one type
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A pure sample of water only
contains water molecules
„ Pure table salt contains only salt
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Pure Substances
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Elements
„ Substances which can not be broken down
into simpler substances by chemical
reactions
„ Fundamental substances
Compounds
„ Two or more elements combined chemically
in a definite and constant ratio
„ Can be broken down into simpler substances
„ Most of matter is in the compound form
Compounds
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Compounds
„ Results from a chemical combination of two or more
elements
„ Can be broken down into elements by chemical processes
„ Properties of the compound not related to the properties of
the elements that compose it
„ Water is composed of hydrogen and oxygen gases
(combined in a 2:1 ratio)
Mixtures
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Something of variable composition
Result from the physical combination of two
or more substances (elements or
compounds)
Made up of two or more types of
substances physically mixed
Not mixed in a fixed ratio, no chemical
combination between the two substances
Compounds vs. Mixtures
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Compounds are not mixtures
„ Cannot be separated by a physical process
„ Can be subdivided by a chemical process
into two or more simpler substances
Mixtures
„ Unlike compounds, mixtures can be
separated by a physical process
„ Retain the properties of their individual
components
Types of Mixtures
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Two types of mixtures:
Homogeneous mixture:
„ Same uniform composition throughout
„ Not possible to see the two substances
present
Heterogeneous mixture:
„ Composition is not uniform throughout the
sample.
„ It contains visibly different parts or phases
Types of mixtures
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Homogenous mixtures
„ A sugar solution
„ 14 karat gold, a mixture of copper and gold
„ Air, a mixture of gases (oxygen, nitrogen)
Heterogeneous mixture
„ Oil and vinegar
„ Raisin cookies
„ Sand
Pure substance
„ i.e. copper (all elements are pure substances)
Classification of Matter
Matter
Pure Substances
Elements
Compounds
Mixture
Homogeneous
Mixture
Heterogeneous
Mixture
Physical Methods
Chemical Methods
Pure Substances
Properties of Matter
Many properties used to identify chemical
substances
„ Two types
„ Physical Properties
„ Chemical Properties
„ Properties can be:
„ Directly observable
„ The interaction of the matter with other
substances
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States of Matter
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Solid
„ Has a rigid, definite shape and definite
volume
Liquid
„ Has an indefinite shape and a definite
volume.
„ It will take the shape of the container it fills
Gas
„ Has an indefinite shape and an indefinite
volume.
„ It will take the shape and completely fill the
volume of the container it fills
(a) Solid (Ice)
Fig3_2
(b) Liquid (Water)
(c) Gas (Steam)
Physical Properties
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Physical Properties
Characteristics of matter that can be
observed or measured without
changing its identity or composition
„ Characteristics that are directly
observable
„ Color, odor, physical state, density,
melting point, boiling point
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Physical Changes
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Cutting a piece of metal, melting ice
Physical Change
A process that alters the
appearance of a substance but
does not change its identity or
composition
„ No new substance is formed
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Most common are changes of state
Chemical Properties
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Chemical Properties
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Describes the ability of a substance to react
and change into a new substance
Properties that matter exhibits as it
undergoes changes in chemical
composition
During a chemical change, the original
substance is converted into one or more
new substances with different chemical and
physical properties
Chemical Change
A change in the fundamental
components of the substance:
„ A substance undergoes a change in
chemical composition
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Also called a chemical reaction
„ Conversion of material(s) into one or
more new substances
„ Wood burning, iron rusting, alka seltzer
tablet into water
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Classifying Properties
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The boiling point of ethyl alcohol is 78 °C
„ Physical property – describes an inherent
characteristic of alcohol, its boiling point
Diamond is very hard
„ Physical property – describes inherent
characteristic of diamond – hardness
Sugar ferments to form ethyl alcohol
„ Chemical property – describes behavior
of sugar, ability to form a new substance
(ethyl alcohol)
Classifying Changes
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Melting of snow
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Burning of gasoline
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Physical change – a change of state but
not a change in composition
Chemical change – combines with
oxygen to form new compounds
Rusting of iron
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Chemical change – combines with
oxygen to form a new reddish-colored
substance (ferric oxide)
Classifying Changes
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Iron metal is melted
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Iron combines with oxygen to form rust
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Physical change – describes a state
change, but the material is still iron
Chemical change – describes how iron
and oxygen combine to make a new
substance, rust (ferric oxide)
Sugar ferments to form ethyl alcohol
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Chemical change – describes how sugar
forms a new substance (ethyl alcohol)
Temperature
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A measure of how hot or cold a substance is
compared to another substance
Fahrenheit Scale, °F
„ Used in USA
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Water’s freezing point = 32°F, boiling point = 212°F
Celsius Scale, °C
„ Used in science (USA) and everyday use in
most of the world
„ Temperature unit larger than the Fahrenheit
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Water’s freezing point = 0°C, boiling point = 100°C
Temperature
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Kelvin Scale, K
SI Unit
„ Used in science
„ Temperature unit same size as Celsius
„ Water’s freezing point = 273 K, boiling point
= 373 K
„ Absolute zero is the lowest temperature
theoretically possible
„ No negative temperatures
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Converting °C to °F
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Units are different sizes
Fahrenheit scale: 180 degree intervals
between freezing and boiling
„ Celsius scale: 100 degree intervals
between freezing and boiling
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180 °F 9 °F 1.8 °F
=
=
100 °C 5 °C 1 °C
212ºF
100ºC
100
Celsius
degrees
180
Fahrenheit
degrees
32ºF
1.8 °F
1 °C
Fig2_9
Boiling point
0ºC
Freezing point
1.8 °F
1 °C
Converting °C to °F
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To convert from °C to °F
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Different values for the freezing points
32 °F
0 °C
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add 32 to the °F value
Different size of the degree intervals in each
scale
T° F
1.8 °F
=
(T°C ) +32
1 °C
Converting °C to K
Temperature units are the same size
„ Differ only in the value assigned to
their reference points
„ K = °C + 273
K = °C + 273
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25°C is room temperature, what is the
equivalent temperature on the Kelvin
scale?
25ºC
ºC+++273
273===298
298K
25
ºC
273
298
KK
25
Example
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A cake is baked at 350 °F. What is
this in Centigrade/Celsius? In Kelvin?
T°F =
1.8 °F
(T°C ) +32
1 °C
1 °C
(T° F − 32 ) = (T° C )
1.8 °F
1 °C
(350 − 32 ) = (T°C )
1.8 °F
T°C = 176.6667 °C
176.7 + 273 =
449.7 K
Energy
Capacity to do work or supply heat
„ Electrical, radiant, mechanical,
thermal, chemical, nuclear
„ Two forms of Energy
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Potential: Stored energy
„ Kinetic: Motion energy
„ All physical changes and chemical
changes involve energy changes
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Forms of Energy
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Potential energy:
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Determined by an objects position
Chemical energy is potential energy stored in the bonds
contained within a molecule. It is released in a chemical
reaction
Kinetic energy
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Energy that matter acquires due to motion
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Converted from the potential energy
All physical changes and chemical changes involve
energy changes
These changes convert energy from one form to another
Units of Energy
The joule (J) is the SI unit of heat energy
„ The calorie (cal) is an older unit used for
measuring heat energy (not an SI unit)
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The amount of energy needed to raise the
temperature of one gram of water by 1°C
4.184 J = 1 cal
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1 kcal = 1000 cal
The Cal is the unit of heat energy in
nutrition
1 Cal = 1000 cal = 1 kcal
Specific Heat
Heat energy is the form of energy
most often released or required for
chemical and physical changes
„ Every substance must absorb a
different amount of heat to reach a
certain temperature
„ Different substances respond
differently when heat is applied
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Specific Heat
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If 4.184 J of heat is applied to:
„ 1 g of water, its temperature is raised by 1 °C
„ 1 g of gold, its temperature is raised by 32 °C
„ Some substances requires large amounts of heat
to change their temperatures, and others require a
small amount
„ The precise amount of heat that is required to
cause a substance to have a rise in temperature is
called a substance’s “specific heat”
Specific Heat
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The amount of heat energy (q) needed to
raise 1 gram of a substance by 1 °C
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Specific to the substance
The higher the specific heat value, the less its
temperature will change when it absorbs heat
SH values given in table 3.7, page 76
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Only for heating/cooling not for changes in state
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heat (qheat
)
J J (or cal) cal
= = o oro
SH = SH =
grams
× ∆T × ∆t g × Cg × Cg × oC
grams
Specific Heat Expression with
Calories and Joules
1 cal is the energy needed to
heat 1 g of water 1 °C
„ 1 cal is 4.184 J
„ Make a conversion factor
from the statements
„
1 cal
4.184 J
SH
=
=
water 1g × 1 o C 1g × 1 o C
Specific Heat Equation
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The rearrangement of the SH equation gives the
expression called the “heat equation”
SH =
heat (q)
mass ( g ) × ∆T
heat ( q ) = SH × mass ( g ) × ∆T
SH
⎛ J ⎞
⎟⎟ × m(g) × ∆T(°C)
q(J) = ⎜⎜
⎝ g × °C ⎠
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q = heat
SH = specific heat (different for each substance)
m = mass (g)
∆T = change in temperature (°C)
= answer in joules
Specific Heat Equation
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Energy (heat) required to change
the temperature of a substance
depends on:
The amount of substance being
heated (g)
„ The temperature change (initial T
and final T in °C)
„ The identity of the substance
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Energy and ΔT
Heat (q) = SH × mass (g) × ∆t
2×
2×
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The amount the temperature of an object
increases depends on the amount of heat added
(q)
„ If you double the added heat energy (q), the
temperature will increase twice as much.
„ When a substance absorbs energy, q is
positive, temperature increases
„ When a substance loses energy, q is
negative, temperature decreases
Converting Energy Units
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Use same problem solving steps as before (Chapter 2)
„ State the given and needed units
„ Write the unit plan to convert the given unit to the final unit
„ State the equalities and the conversion factors
„ Set up the problem to cancel the units
Pepsi One™ contains 1 Calorie per can.
How many joules is this?
1 Cal = 1000 cal
4.184 J = 1 cal
1 Cal 1000 cal 4.184 J
= 4184 J
1 cal
1 Cal
Calculating Mass Using Specific Heat
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The 4184 J from the Pepsi One™
will heat how many grams of water
from 0°C to boiling?
q
m=
SH × ΔT
4184 J 1°C×1g
4.184 J 100 °C
=10 g = 10 mL
Calculating Mass Using Specific Heat
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How many grams of water would reach
boiling if the water started out at room
temperature (25°C)?
q
m=
SH × ΔT
4184 J 1 °C ×1 g
° − °25
C°
4.184 J 10075
=
13.33 g = 13.33 mL
Calculating The Temperature
Change Using Specific Heat Values
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If 50.0 J of heat is applied to 10.0 g
of iron, by how much will the
temperature of the iron increase?
50.0 J g × °C
= 11.11 °C
0.45 J 10.0 g
Q = SH × m × ΔT
Q
ΔT =
SH × m
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end