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States of Matter
Chapter 3
Matter and Energy
States of Matter (cont.)
Gases
1
Liquids
Properties
• Characteristics of the substance under
observation
• Properties are:
– Directly observable
– The way something interacts with other
substances in the universe
Universe Classified
• Matter: the part of the universe that has
mass and volume
• Chemistry is the study of matter
– The properties of different types of matter
– The wayy matter changes
g and behaves when
influenced by other matter and/or energy
Properties of Matter
• Physical Properties: the characteristics of
matter that can be changed without changing
its composition
– Characteristics that are directly observable
• Chemical Properties: the characteristics that
determine how the composition of matter
changes as a result of contact with other
matter or the influence of energy
– Characteristics that describe the behavior of matter
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Chemical Properties
Chemical Properties (cont.)
• One commonly cited chemical property is
flammability, the ease with which a
substance burns in a flame. Burning is a
chemical reaction.
Classify Each of the following
as a Physical or Chemical Property
• Ethyl alcohol boiling at 78°C.
• Hardness of a diamond.
• Sugar fermenting to form ethyl alcohol.
Classify Each of the following
as a Physical or Chemical Property (cont.)
• Ethyl alcohol boiling at 78°C.
– Physical property: boiling point is a associated with a phase
change. It describes an inherent characteristic of alcohol.
• Hardness of a diamond.
– Physical property: describes an inherent characteristic of
diamond – hardness
• Sugar fermenting to form ethyl alcohol.
– Chemical property: describes behavior of sugar – forming a
new substance (ethyl alcohol) through a chemical reaction
3
Changes in Matter
Chemical Change
• Physical changes: changes to matter that do not
result
lt in
i a change
h
the
th fundamental
f d
t l components
t
that make up the substance
– State changes: boiling, melting, condensing
• Chemical changes: changes that involve a change
in the fundamental components
p
of the substance
– Produce new substances
– Chemical reactions occur
– Reactants → Products
Chemical Change (cont.)
• Chemical change involves a chemical
reaction. At least one new substance
is formed.
Classify Each of the following
as a Physical or Chemical Change
• Iron metal melting.
• Iron combining with oxygen to form rust.
• Sugar fermenting to form ethyl alcohol.
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Classify Each of the following
as a Physical or Chemical Change (cont.)
• Iron metal melting.
– Physical change: describes a state change, but the material is
still iron
• Iron combining with oxygen to form rust.
– Chemical change: describes how iron and oxygen react to
make a new substance, rust
• Sugar fermenting to form ethyl alcohol.
– Chemical change: describes how sugar forms a new
substance (ethyl alcohol) via a chemical reaction
Classification of Matter
Matter
Pure Substance
Constant Composition
Homogeneous
Mixture
Variable Composition
• Homogeneous: uniform throughout, appears to be one thing
– Pure substances
b
– Solutions (homogeneous mixtures)
• Heterogeneous: non-uniform, contains regions with different
properties than other regions
Elements and Compounds
• Elements: substances that cannot be broken
d
down
into
i
simpler
i l substances
b
by
b chemical
h i l
reactions
• Most substances are chemical combinations of
elements. These combinations are called
compounds.
– Compounds are made of elements
– Compounds can be broken down into elements
– Properties of the compound not related to the properties of the
elements that compose it
– Same chemical composition at all times
Pure Substances
• Pure substances
– All samples have the same physical and chemical
properties
– Constant composition: all samples have the same
composition
– Homogeneous
– Separate into components based on chemical
properties
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Mixtures
Pure Substances vs. Mixtures
• Mixtures
– Different samples may show different
properties
– Variable composition
– Homogeneous or heterogeneous
p
into components
p
based on p
physical
y
– Separate
properties
• All mixtures are made of pure substances
Solutions
Solutions (cont.)
• A solution is a homogeneous mixture.
• Phase can be gaseous, liquid, or solid.
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Identity Each of the following as a Pure Substance,
Homogeneous, Mixture, or Heterogeneous Mixture.
Identity Each of the following as a Pure Substance,
Homogeneous Mixture, or Heterogeneous Mixture (cont.)
• Gasoline
• Gasoline
– A homogenous mixture
• A stream with gravel on the bottom
• A stream with gravel on the bottom
• Copper metal
– A heterogeneous mixture
• Copper metal
– A pure substance (all elements are pure
substances)
Separation of Mixtures
Separation of Mixture (cont.)
• Mixtures can be separated based on different
pphysical
y
pproperties
p
of the components
p
– Physical change
Different Physical Property
Technique
Boiling point
Distillation
State of matter
(solid/liquid/gas)
Adherence to a surface
Chromatography
Volatility
Evaporation
Filt ti
Filtration
7
Separation of a Mixture (cont.)
Another Look at Matter
Energy and Energy Changes
Energy and Energy Changes
• Energy: ability to do work or produce heat
• Potential Energy:
energy due to
composition or position
• Energy may affect matter.
• Kinetic Energy: energy
due to motion
– - ½ mv2
– Chemical
Chemical, mechanical
mechanical, thermal
thermal, electrical,
electrical radiant,
radiant
sound, nuclear
– Potential and kinetic
– e.g. Raise its temperature, eventually causing a state
g , or cause a chemical change
g such as
change,
decomposition
• All physical changes and chemical changes
involve energy changes.
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Energy and Energy Changes (cont.)
Temperature and Heat
• Law of Conservation of Energy: energy can
be converted from one form to another, but
cannot be created or destroyed
• Heat: a flow of energy due to a temperature
difference
• Temperature: a measure of the random
motions of the components of a substance
Temperature and Heat (cont.)
Exothermic vs. Endothermic
• System: that part of the universe that we wish to
study
t d
• Surroundings: everything else in the universe
• Exothermic process: a process that results in the
evolution of heat
- Example: when a match is struck, it is an
exothermic p
process because energy
gy is produced
p
as
heat.
• Endothermic process: absorbs heat
- Example: melting ice to form liquid water is an
endothermic process because the ice absorbs heat in
order to melt
9
Exothermic Process
Units of Energy
• One calorie = amount of energy needed to
raise the temperature of one gram of water by
1°C
– kcal = energy needed to raise the temperature of
1000 g of water 1°C
• joule
– 4.184 J = 1 cal
• In nutrition, calories are capitalized.
– 1 Cal = 1 kcal
Example - Converting Calories to Joules
Energy & Temperature of Matter
Convert 60.1 cal to
joules.
• The amount the temperature of an object increases
depends on the amount of heat added (q).
(q)
1 cal = 4.184 joules
4.184 J
60 1cal ×
60.1cal
= 251J
1 cal
– If you double the added heat energy the temperature
will increase twice as much.
• The amount the temperature of an object increases
when heat is added depends on its mass
– Iff you ddouble
bl the
h mass iit will
ill take
k twice
i as muchh heat
h
energy to raise the temperature the same amount.
10
Specific Heat Capacity
Specific Heat Capacity
• Specific heat (s): the amount of energy
required to raise the temperature of one
gram of a substance by one degree Celsius
By definition , the specific heat of water is 4.184
J
g °C
Amount of Heat = Specific Heat x Mass x Temperature Change
Q = s x m x ∆T
Example #1:
Calculate the amount of heat energy (in joules)
needed to raise the temperature of 7.40 g of
water from 29.0°C to 46.0°C.
Example #1 (cont.)
Specific heat of water = 4.184
J
g °C
Mass = 7.40 g
Temperature change = 46.0°C – 29.0°C = 17.0°C
Q = s • m • ∆T
Heat = 4.184
J
× 7.40g ×17.0°C = 526 J
g °C
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Example #2
A 1.6 g sample of metal that appears to be
gold
ld requires
i 5.8
5 8 J to raise
i the
h temperature
from 23°C to 41°C. Is the metal pure gold?
Example #2
Q = s × m × ∆T
Q
m × ∆T
∆T = 41°C - 23°C = 18°C
s=
s=
J
5.8 J
= 0.20
1.6 g x 18°C
g °C
Table 10.1 lists the specific heat of gold as 0.13
Therefore the metal cannot be pure gold.
J
g °C
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