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The Flow of Energy—Heat and Work
The temperature of lava from a volcano ranges
from 550°C to 1400°C. As lava flows, it loses heat
and begins to cool. You will learn about heat flow and why some substances cool down or heat up more quickly than others.
The Flow of Energy—Heat and Work >
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Energy Transformations
Energy Transformations
In what direction does heat flow?
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The Flow of Energy—Heat and Work Energy Transformations
Heat, represented by q, is energy that
transfers from one object to another because of a temperature difference between them.
Heat always flows from a warmer object to a cooler object.
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The Flow of Energy—Heat and Work Energy Transformations
Thermochemistry is the study of energy
changes that occur during chemical reactions and changes in state.
The energy stored in the chemical bonds of a substance is called chemical potential
energy.
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The Flow of Energy—Heat and Work Energy Transformations
When fuel is burned in a car engine, chemical potential energy is released and is used to do work.
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Exothermic and
Endothermic Processes
Exothermic and Endothermic Processes
What happens in endothermic and exothermic processes?
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The Flow of Energy—Heat and Work Exothermic and
Endothermic Processes
In an endothermic process, the system gains heat as the surroundings cool
down.
In an exothermic process, the system loses heat as the surroundings heat up.
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The Flow of Energy—Heat and Work Exothermic and
Endothermic Processes
In studying energy changes, you can define
a system as the part of the universe on which
you focus your attention. The surroundings
include everything else in the universe.
The law of conservation of energy states
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The Flow of Energy—Heat and Work Exothermic and
Endothermic Processes
An endothermic process is one that
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The Flow of Energy—Heat and Work Exothermic and
Endothermic Processes
An exothermic process is one that
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Practice Problems for Conceptual Problem 17.1
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Units for Measuring Heat Flow
Units for Measuring Heat Flow
In what units is heat flow measured?
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The Flow of Energy—Heat and Work Units for Measuring Heat Flow
Heat flow is measured in two common units, the calorie and the joule.
The energy in food is usually expressed in Calories.
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Heat Capacity and Specific Heat
Heat Capacity and Specific Heat
On what two factors does the heat capacity of an object depend?
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The Flow of Energy—Heat and Work Heat Capacity and Specific Heat
The heat capacity of an object depends on both its mass and its chemical
composition.
The amount of heat needed to increase the temperature of an object exactly 1°C is the
heat capacity of that object.
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The Flow of Energy—Heat and Work Heat Capacity and Specific Heat
The specific heat capacity, or simply the
specific heat, of a substance is the amount
of heat it takes to raise the temperature of 1 g of the substance 1°C.
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The Flow of Energy—Heat and Work Heat Capacity and Specific Heat
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The Flow of Energy—Heat and Work Heat Capacity and Specific Heat
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The Flow of Energy—Heat and Work Heat Capacity and Specific Heat
Because it is mostly water, the filling of a hot apple pie is much more likely to burn your
SAMPLE PROBLEM
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SAMPLE PROBLEM
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SAMPLE PROBLEM
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SAMPLE PROBLEM
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Practice Problems for Sample Problem 17.1
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Section Quiz
-or-Continue to: Launch:
Assess students’ understanding of the concepts in Section
17.1 Section Quiz.
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1. The energy released when a piece of wood is burned has been stored in the wood as
a. sunlight.
b. heat.
c. calories.
d. chemical potential energy.
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2. Which of the following statements about heat is false?
a. Heat is the same as temperature.
b. Heat always flows from warmer objects to cooler objects.
c. Adding heat can cause an increase in the temperature of an object.
d. Heat cannot be specifically detected by senses or instruments.
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3. Choose the correct words for the spaces: In an endothermic process, the system
________ heat when heat is ________ its surroundings, so the surroundings
_____________.
a. gains, absorbed from, cool down.
b. loses, released to, heat up.
c. gains, absorbed from, heat up.
d. loses, released to, cool down.
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4. Which of the relationships listed below can be used to convert between the two units used to measure heat transfer?
a. 1 g = 1ºC
b. 1 J = 0.2390 cal
c. 1ºC = 1 cal
d. 1 g = 4.184 J
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5. Assuming that two samples of different materials have equal mass, the one that becomes hotter from a given amount of heat is the one that
a. has the higher specific heat capacity.
b. has the higher molecular mass.
c. has the lower specific heat capacity.
d. has the higher density.
