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Chapter 10
Energy
Chapter 10 Review p.297- Key Terms
energy (10.1)
potential energy (10.1)
kinetic energy (10.1)
law of conservation of energy (10.1)
work (10.1)
state function (10.1) temperature (10.2)
heat (10.2)
system (10.3)
surroundings (10.3)
exothermic (10.3)
endothermic (10.3)
thermodynamics (10.4)
first law of thermodynamics (10.4)
internal energy (10.4)
calorie (10.5)
joule (10.5)
specific heat capacity (10.5)
enthalpy (10.6)
calorimeter (10.6)
Hess's law (10.7)
fossil fuels (10.9)
petroleum (10.9)
natural gas (10.9)
coal (10.9)
greenhouse effect (10.9)
energy spread (10.10) matter spread (10.10)
entropy (10.10)
second law of thermodynamics (10.10) spontaneous process (10.10)
Summary
1. One of the fundamental characteristics of energy is that it is
conserved. Energy is changed in form but it is not produced or
consumed in a process. Thermodynamics is the study of energy and
its changes.
2. In a process some functions - called state functions - depend only
on the beginning and final states of the system, not on the specific
pathway followed. Energy is a state function. Other functions, such
as heat and work, depend on the specific pathway followed and are
not state functions.
3. The temperature of a substance indicates the vigor of the random
motions of the components of that substance. The thermal energy of
an object is the energy content of the object as produced by its
random motions.
Summary (cont’d)
4. Heat is a flow of energy between two objects due to a
temperature difference in the two objects. In an exothermic
reaction, energy as heat flows out of the system into its
surroundings. In an endothermic process, energy as heat flows
from the surroundings into the system.
5. The internal energy of an object is the sum of the kinetic
(due to motion) and potential (due to position) energies of the
object. Internal energy can be changed by two types of energy
flows, work (w) and heat (q): ∆E = q + w.
6. A calorimeter is used to measure the heats of chemical
reactions. The common units for heat are joules and calories.
Summary (cont’d)
7. The specific heat capacity of a substance (the energy required to
change the temperature of one gram of the substance by one Celsius
degree) is used to calculate temperature changes when a substance is
heated.
8. The change in enthalpy for a process is equal to the heat for that
process run at constant pressure.
9. Hess's law allows the calculation of the heat of a given reaction
from known heats of related reactions.
10. Although energy is conserved in every process, the quality
(usefulness) of the energy decreases with each use.
11. Our world has many sources of energy. The use of these sources
affects the environment in various ways.
Summary (cont’d)
12. Natural processes occur in the direction that leads to an
increase in the disorder (entropy) of the universe. The principal
driving forces for processes are energy spread and matter spread.
Active Learning Questions
1. Look at Figure 10.1 in your text. Ball A has stopped moving.
However, energy must be conserved. So what happened to the
energy of ball A?
Active Learning Questions (cont’d)
2. A friend of yours reads that the process of water freezing is
exothermic. This friend tells you that this can't be true because
exothermic implies "hot," and ice is cold. Is the process of water
freezing exothermic? If so, explain this process so your friend can
understand it. If not, explain why not.
3. You place hot metal into a beaker of cold water.
a. Eventually what is true about the temperature of the metal
compared to that of the water? Explain why this is true.
b. Label this process as endothermic or exothermic if we consider
the system to be
i. the metal. Explain; ii. the water. Explain.
4. What does it mean when the heat for a process is reported with a
negative sign?
Active Learning Questions (cont’d)
5. You place 100.0 g of a hot metal in 100.0 g of cold water.
Which substance (metal or water) undergoes a larger temperature
change? Why is this?
6. Explain why aluminum cans make good storage containers for
soft drinks. Styrofoam cups can be used to keep coffee hot and
cola cold. How can this be?
7. In Section 10.7(p.285), two characteristics of enthalpy
changes for reactions are listed. What are these characteristics?
Explain why these characteristics are true.
8. What is the difference between quality and quantity of
energy? Are both conserved? Is either conserved?
Active Learning Questions (cont’d)
9. What is meant by the term driving forces? Why are matter
spread and energy spread considered to be driving forces?
10. Give an example of a process in which matter spread is a
driving force and an example of a process in which energy spread
is a driving force, and explain each. These examples should be
different from the ones given in the text.
QUESTION
The energy associated with the position of an object is known as
1.
2.
3.
4.
potential energy
internal energy
mechanical energy
positional energy
QUESTION
When a negatively charged electron absorbs a photon of light and
jumps up to a higher energy level, work is being done on the
electron in order to move it further away from the positive
nucleus. In classical mechanics (not quantum mechanics) we
traditionally think of work as
1. mass x acceleration
2. force x distance
3. ½ mass x velocity2
4. force/area
QUESTION
A property of a system that changes independently of its pathway
is referred to as a(n)
1.
2.
3.
4.
intensive property
extensive property
independent function
state function
QUESTION
Heat is ____________ while temperature is ________________.
1.
2.
3.
4.
a form of energy; a loss of energy
a flow of energy due to difference in temperature; a
measure of the random thermal motion of particles
high grade energy; low grade energy
an energy form that flows from hot to cold areas; a
measure of potential energy
QUESTION
An example of an endothermic process is
1.
2.
3.
4.
fireworks exploding in the night sky
the melting of a glacier due to global warming
the combustion of gasoline in an internal combustion
engine
rolling a ball down a hill
QUESTION
The metal gallium (atomic number 31) has the properties
normally associated with a metal, but it has the unusual property
of melting in your hand. If Ga represents the system, then the
process of melting in your hand leads to a positive __ of the
system, due to __.
1.
2.
3.
4.
∆E ; q
∆T ; ∆m
∆E ; w
w;m
QUESTION
One calorie of energy is equivalent to
1.
2.
3.
4.
1.0 kilojoule
2.35 millijoules
4.184 joules
a temperature change of 1 K
QUESTION
The correct units for specific heat capacity are
1.
2.
3.
4.
cal
cal/g
J/g ºC
J/mole
QUESTION
The heat specific capacity of lead is 0.13 J/g ºC. How many
joules of heat would be required to raise the temperature of 150.0
g of Pb from 25ºC to 100ºC?
1.
2.
3.
4.
130 J
1.0 x 103 J
1.5 x 103 J
7.5 x 102 J
QUESTION
Under conditions of constant pressure, the heat change that
occurs during a chemical change is equal to
1.
2.
3.
4.
∆T
∆E
∆w
∆H
QUESTION
Calculate ∆H for the reaction: SO2 + ½O2
Given (1) S + O2
SO2
(2) 2S + 3O2
2SO3
1. -693 kJ
2. 101 kJ
3. 693 kJ
4. -99 kJ
SO3 ∆H = ?
∆H = -297 kJ
∆H = -792 kJ
QUESTION
When photosynthesis occurs, highly dispersed solar energy is
1.
2.
3.
4.
degraded
refined into concentrated biomass energy
turned into heat
reflected into space
QUESTION
Due to the fact that CO2 absorbs light and releases the energy as
heat, it is referred to as a greenhouse gas (GHG). Other GHGs in
the earth’s atmosphere include
1. H20 and CH4
2. H2O and N2
3. CH4 and N2
4. H2O and O2
QUESTION
The second law of thermodynamics can be stated as
1.
2.
3.
4.
Energy is conserved.
Internal energy of a closed system is constant.
Energy is degraded when it is used.
The entropy of the universe is always increasing.