Transcript Introductory Chemistry: A Foundation FOURTH EDITION by

Introductory Chemistry:
A Foundation
FIFTH EDITION
by Steven S. Zumdahl
University of Illinois
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1
Matter and Energy
Chapter 3
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2
Universe Classified
• Matter is the part of the universe that has
mass and volume
• Energy is the part of the universe that has
the ability to do work
• 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
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3
States of Matter
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4
Properties
•
Characteristics of the substance under observation
•
Properties can be either
directly observable or
the manner something interacts with other substances
in the universe
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5
Properties of Matter
• Physical Properties are the characteristics of
matter that do not affect the composition of the
substance
– Characteristics that are directly observable
• Chemical Properties are 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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6
Classify Each of the following as
Physical or Chemical Properties
The boiling point of ethyl alcohol is 78°C.
Diamond is very hard.
Sugar ferments to form ethyl alcohol.
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Classify Each of the following as
Physical or Chemical Properties
The boiling point of ethyl alcohol is 78°C.
– Physical property – describes inherent characteristic of
alcohol – 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 –
forming a new substance (ethyl alcohol)
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8
Changes in Matter
• Physical Changes are changes to matter that do
not result in a change the fundamental components
that make that substance
– State Changes – boiling, melting, condensing
• Chemical Changes involve a change in the
fundamental components of the substance
– Produce a new substance
– Chemical reaction
– Reactants  Products
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9
Physical Changes:
The Three States of Water
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10
Chemical
Changes:
Electrolysis - the
Decomposition Of
Water by Electric
Current
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11
Classify Each of the following as
Physical or Chemical Changes
Iron metal is melted.
Iron combines with oxygen to form rust.
Sugar ferments to form ethyl alcohol.
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12
Classify Each of the following as
Physical or Chemical Changes
Iron is melted.
– Physical change – describes a state change, but the
material is still iron
Iron combines with oxygen to form rust..
– Chemical change – describes how iron and oxygen
react to make a new substance, rust
Sugar ferments to form ethyl alcohol.
– Chemical change – describes how sugar forms a new
substance (ethyl alcohol)
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13
Elements and Compounds
• Substances which can not be broken down into
simpler substances by chemical reactions are
called elements
• Most substances are chemical combinations of
elements. These are called compounds.
– Compounds are made of elements
– Compounds can be broken down into elements
– Properties of the compound are not related to the
properties of the elements that compose it
– Same chemical composition at all times
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14
Classification of Matter
Matter
Pure Substance
Constant Composition
Homogeneous
Mixture
Variable Composition
• Homogeneous = uniform throughout, appears to be one
thing
– pure substances
– solutions (homogeneous mixtures)
• Heterogeneous = non-uniform, contains regions with
different properties than other regions
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15
Pure Substances vs. Mixtures
• Pure Substances
– All samples have the same physical and chemical properties elements or compounds
– Constant Composition  all samples have the same composition
– Homogeneous
– Separate into components based on chemical properties
• Mixtures
– Different samples may show different properties
– Variable composition
– Homogeneous or Heterogeneous
– Separate into components based on physical properties
• All mixtures are made of pure substances
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Identity Each of the following as a Pure
Substance, Homogeneous Mixture or
Heterogeneous Mixture
Table salt in water
Sand in water
Copper metal
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Identity Each of the following as a Pure
Substance, Homogeneous Mixture or
Heterogeneous Mixture
Table salt in water
– a homogenous mixture - solution
Sand in water
– a heterogeneous mixture
Copper metal
– A pure substance (all elements are pure substances)
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18
Separation of Mixtures
• Separate mixtures based on different
physical properties of the components
– Physical change
Different Physical Property
Technique
Boiling Point
Distillation
State of Matter
(solid/liquid/gas)
Adherence to a Surface
Filtration
Chromatography
Volatility
Evaporation
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19
Distillation
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20
Energy and Energy Changes
• Capacity to do work
– chemical, mechanical, thermal, electrical,
radiant, sound, nuclear
• Energy may affect matter
– e.g. raise its temperature (heat energy),
eventually causing a state change
– All physical changes and chemical changes
involve energy changes
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21
Heat
Heat: a flow of
energy due to a
temperature
difference
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Heat
•
Heat: a flow of energy due to a temperature
difference
1. Exothermic = A process that results in the
evolution of heat.
• Example: when a match is struck, it is an
exothermic process because energy is produced as
heat.
2. Endothermic = A process that absorbs energy.
• Example: melting ice to form liquid water is an
endothermic process.
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Units of Energy
• One calorie is the 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
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Example - Converting Calories to Joules
Convert 60.1 cal to joules:
1 cal  4.184 joules
4.184 J
60.1cal 
 251J
1 cal
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Energy and the Temperature of Matter
• The amount the temperature of an object
increases depends on the amount of heat
added (Q).
– If you double the added heat energy the
temperature will increase twice as much.
• The amount the temperature of an object
increases depends on its mass
– If you double the mass it will take twice as
much heat energy to raise the temperature the
same amount.
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Specific Heat Capacity
• Specific Heat (s) is the amount of energy
required to raise the temperature of one
gram of a substance by one Celsius degree
J
By definition, the specific heat of water is 4.184
g C
Amount of Heat = Specific Heat x Mass x Temperature Change
Q = s x m x T
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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:
JJ
Specific Heat of Water = 4.184
gg-CC
Mass = 7.40 g
Temperature Change = 46.0°C – 29.0°C = 17.0°C
Q = s x m x T
J
Heat  4.184
 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 requires 5.8 J to raise the temperature
from 23°C to 41°C. Is the metal pure gold
(specific heat)?
Q  s  m  T
Q
s
m  T
T  41C - 23C  18C
5.8 J
J
s
 0.20
1.6 g x 18C
g C
Table 3.2 lists the specific heat of gold as 0.13
Therefore the metal cannot be pure gold.
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J
g C
29