Chemistry 17.1

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Chemistry 17.1

Chapter 17

Section 1

© Copyright Pearson Prentice Hall

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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.

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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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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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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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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 that in any chemical or physical process, energy is neither created nor destroyed.

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An endothermic process is one that absorbs heat from the surroundings.

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An exothermic process is one that releases heat to its surroundings.

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Conceptual Problem 17.1


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Conceptual Problem 17.1


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Conceptuall Problem 17.1


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Practice Problems for Conceptual Problem 17.1

Problem Solving 17.1 Solve Problem 1 with the help of an interactive guided tutorial.



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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 andSpecific 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 andSpecific 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 andSpecific Heat

Water releases a lot of heat as it cools. During freezing weather, farmers protect citrus crops by spraying them with water.

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Because it is mostly water, the filling of a hot apple pie is much more likely to burn your tongue than the crust.

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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

Problem Solving 17.4 Solve Problem 4 with the help of an interactive guided tutorial.


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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.

17.1 Section Quiz.

END OF SHOW

Chemistry 17.1

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