Chapter 16 Thermal Energy and Heat

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Chapter 16
THERMAL ENERGY AND HEAT
Chapter 16.1 Thermal Energy and Matter
Introduction
1. What did most
scientists thought
about heat in the
1700s?
Scientists thought heat
was a fluid called
caloric.
It would flowed between
objects.
Chapter 16 Thermal Energy and Matter
Benjamin Thompson
Count Rumford
2. Who was Count Rumford?
American-born scientist
(1753-1814)
3. What concept did he
challenged?
The Concept of heat.
4. How did he do this?
Chapter 16.1 Thermal Energy and Matter
 A brass cylinder is drilled to make a cannon barrel.
 Water is used to cool the brass so that it did not melt.
 Rumford observed that the brass became hot as long
as the drilling continued, producing enough heat to
boil the water.
 Soon after the drilling stopped, however, the water
stopped boiling
Chapter 16.1 Thermal Energy and Matter
A. Work and Heat
1. Summary  A drill is a
machine that does
work on the cannon.
The more work done by
the drill, the more that
friction causes the
cannon to heat up.
2. What is Heat?
It is the transfer of
thermal energy from
one object to another
because of a
temperature difference.
Chapter 16.1 Thermal Energy and matter
B. Temperature
3. What is temperature?
It is a measure of how
hot or cold an object is
compared to a
reference point.
4. What is the relationship
between temperature,
speed of the particles, and
average kinetic energy?
As the temperature
increases, speed of the
particle increases, average
kinetic energy increases.
Chapter 16.1 Thermal Energy and Matter
C. Thermal Energy
5. Recall that thermal
energy is the total
potential and kinetic
energy of all the
particles in an object
6. What does thermal
energy depend on?
Mass
Temperature
Phase of the object
Chapter 16.1 Thermal Energy and Matter
D. Thermal Contraction
and Expansion
7. What is thermal
expansion?
It is an increase in the
volume of a material
due to a temperature
increase.
8. Why does this occur?
It occurs when
particles of matter
move farther apart as
temperature increases.
Chapter 16.1 Thermal Energy and Matter
D. Thermal contraction
and expansion
9. What is thermal
contraction?
It is a decrease in the
volume of a material
due to a temperature
decrease.
10. Why does this
occurs?
It occurs when
particles of matter
move closer together as
temperature decrease.
Chapter 16.1 Thermal Energy and Matter
E. Specific Heat
11. What is Specific
Heat?
It is the amount of
heat needed to raise
the temperature of one
gram of a material by
one degree Celsius.
12. What is the relationship
between specific heat
and temperature?
The lower a material’s
specific heat, the more its
temperature rises when a
given amount of energy
is absorbed by a given
mass.
Chapter 16.1 Thermal Energy and Matter
E. Specific Heat
13. What is the formula
for specific heat?
Q = m x c x ∆T
Specific Heats of
Selected Materials
Material
(at 100 kPa)
Specific Heat
(j/g•C°)
Water
4.18
Plastic
1.84--2.09
Air
1.01
Iron
0.449
Silver
0.235
Chapter 16.1 Thermal Energy and Matter
Name
Symbol
Unit
Equation
Heat
Q
Joules
Q = m x c x ∆T
Mass
M
Grams
M = Q / (c x ∆T)
Specific heat
C
j/g•C°
C = Q / (m x ∆T)
Change in
Temperature
∆T
C°
∆T = Q / (m x c)
Chapter 16.1 Thermal Energy and Matter
Page 477 Math Skills, Calculating Specific Heat
List, formula, sub and answer
21, 375 joules
Page 477 Math Practice
1. 35.5 kJ
2. 34 kJ
3. 3.8 C°
4. 10.0 C°
5. 42 g
Chapter 16.1 Thermal Energy and Matter
F. Measuring Heat
Changes
14. What is calorimeter?
It is an instrument
used to measure
changes in thermal
energy.
15. What principle does
the calorimeter use?
Heat flows from a
hotter object to a
colder object until both
reach the same
temperature.
Chapter 16.1 Thermal Energy and Matter
F. Measuring Heat
Changes
16. Why does this principle
work?
According to the law of
conservation for energy,
the thermal energy
released by a test sample
is equal to the thermal
energy absorbed by its
surroundings.
Page 478 Math Practice
Problems 10 & 11
10. 7800 joules
11. 43.5 C°
Chapter 16.2 Heat and Thermodynamics
Introduction
What are the three
ways to transfer heat?
Conduction
Convection
Radiation
1.
Chapter 16.2 Heat and Thermodynamics
A. Conduction
What is conduction?
It is the transfer of
thermal energy with no
overall transfer of matter
It occurs within a
material or between
materials that are
touching.
1.
2. What is the rate of
conduction in the phases
of matter?
In general, conduction
occurs faster in solids,
than liquid, than in
gases.
Chapter 16.2 heat and Thermodynamics
A. Conduction
3. What are the types of
materials used in
conduction?
Thermal conductor is a
material that transfers
thermal energy well.
Metals are example.
Thermal Insulator is a
material that does not
transfer thermal energy
well.
Wood and glass are
examples.
Chapter 16.2 heat and Thermodynamics
Chapter 16.2 Heat and Thermodynamics
B. Convection
4. What is convection?
It is the transfer of
thermal energy when
particles of a fluid move
from one place to
another.
5. What is a convection
current?
It occurs when a fluid
circulates in a loop as it
alternately heats up and
cools down.
Chapter 16.2 Heat and Thermodynamics
Chapter 16.2 Heat and Thermodynamics
C. Radiation
6. What is radiation?
It is the transfer of
energy by waves moving
through space.
7. What is the
relationship between
temperature and radiate
energy?
As an object’s
temperature increases,
the rate at which it
radiates energy
increases.
Chapter 16.2 Heat and Thermodynamics
Chapter 16.2 Heat and Thermodynamics
D. Thermodynamics
8. What is
thermodynamics?
It is the study of
conversions between
thermal energy and other
forms of energy.
Chapter 16.2 Heat and Thermodynamics
D. thermodynamics
9. What did James Prescott
Joule do?
He carefully measured the
energy changes in a
system.
He found that the work
done almost exactly
equaled the thermal energy
gained by the water.
Chapter 16.2 Heat and Thermodynamics
D. Thermodynamics
10. What are the laws of
Thermodynamics?
1st Law of
Thermodynamics 
Energy is conserved.
Chapter 16.2 Heat and Thermodynamics
D. Thermodynamics
2nd Law of
Thermodynamics 
Thermal energy can flow
from colder objects to
hotter objects only if
work is done on the
system.
Chapter 16.2 Heat and Thermodynamics
D. Thermodynamics
3rd Thermodynamics 
Absolute zero cannot be
reached.
Chapter 16.3 Using Heat
A. Heat Engines
What is a heat
engine?
It is a system that
performs the conversion
of heat or thermal energy
to Mechanical work.
1.
Chapter 16.3 Using Heat
A. Heat Engines
2. What are the types of
heat engines?
External combustion
Internal combustion
Chapter 16.3 Using Heat
A. Heat Engines
3. What is an external
combustion engine?
It is an engine that burns
fuel outside the engine.
4. What is an example?
A Steam engine.
Chapter 16.3 Using Heat
A. Heat Engines
5. What is an internal
combustion engine?
It is a heat engine in
which the fuel burns
inside the engine.
6. What is an example?
Most cars use them.
Chapter 16.3 Using Heat
7. Describe the sequence of events in one cylinder of a
four-stroke engine.
Chapter 16.3 Using Heat
B. Heating Systems
8. What was the
principal method of
heating buildings at the
start of the industrial
revolution?
Wood-burning fireplaces
Chapter 16.3 Using Heat
B. Heating Systems
9. What type of heating
system is used today?
Central heating system
which heats many rooms
from one central location
usually found in the
basement.
Chapter 16.3 Using heat
B. Heating Systems
10. What are the
different types of heating
systems?
Hot-Water Heating
Steam Heating
Electric Baseboard
Heating
Forced-Air Heating
Chapter 16.3 Using Heat
B. Heating Systems
Hot-Water Heating
System 
Within the pipes of a hotwater heating system, the
water circulates in a
convection current. In
each room, the air moves
in a convection current.
Chapter 16.3 Using Heat
B. Heating Systems
Steam Heating System 
very similar to hot-water
heating except that
steam is used instead of
hot water.
Chapter 16.3 Using Heat
B. Heating Systems
Electric Baseboard
Heating System  The
hot coil heats the air near
it by conduction and
radiation. Then
convection circulates the
warm air to heat the
room.
Chapter 16.3 Using Heat
B. Heating Systems
Forced-Air Heating System

The hot air enters the room
through a supply vent in
the floor. The hot air rises
as cooler, denser air in the
room sinks. The cooler air
returns to the furnace
through the return vent.
Chapter 16.3 Using Heat
C. Cooling Systems
11. What is a cooling
system?
A system that takes heat
from one area to another.
Chapter 16.3 Using Heat
C. Cooling Systems
12. What is a heat pump?
It is a device that
reverses the normal flow
of thermal energy.
13. What is a refrigerant?
It is a fluid that vaporizes
and condenses inside the
tubing of a heat pump.
Chapter 16.3 Using Heat
C. Cooling systems
14. Important statements
Thermal energy flows
spontaneously from hot
to cold objects.
Heat pumps must do
work on a refrigerant in
order to reverse the
normal flow of thermal
energy.
Chapter 16.3 Using Heat
C. Cooling systems
15. What are
refrigerators?
It is a heat pump that
transfers thermal energy
from the cold food
compartment to the
warm room.
Chapter 16.3 Using Heat
C. Cooling systems
16. What are air
conditioners?
A device used to cool the
air in your home.
Outside air is heated as a
fan blows it through the
condenser coil. Inside the
room, a fan draws in warm
air through the evaporator
coil. The fan blows cooled
air out into the room.
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