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Slide 1 of 34 Chemistry 17.1. © Copyright Pearson Prentice Hall Slide 2 of 34 The Flow of Energy—Heat and Work The temperature of lava from a volcano.

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Presentation on theme: "Slide 1 of 34 Chemistry 17.1. © Copyright Pearson Prentice Hall Slide 2 of 34 The Flow of Energy—Heat and Work The temperature of lava from a volcano."— Presentation transcript:

1 Slide 1 of 34 Chemistry 17.1

2 © Copyright Pearson Prentice Hall Slide 2 of 34 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. 17.1

3 © Copyright Pearson Prentice Hall The Flow of Energy—Heat and Work > Slide 3 of 34 Energy Transformations In what direction does heat flow? 17.1

4 Slide 4 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

5 Slide 5 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

6 Slide 6 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

7 © Copyright Pearson Prentice Hall The Flow of Energy—Heat and Work > Slide 7 of 34 Exothermic and Endothermic Processes What happens in endothermic and exothermic processes? 17.1

8 Slide 8 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

9 Slide 9 of 34 © Copyright Pearson Prentice Hall > 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 that in any chemical or physical process, energy is neither created nor destroyed. 17.1

10 Slide 10 of 34 © Copyright Pearson Prentice Hall > The Flow of Energy—Heat and Work Exothermic and Endothermic Processes An endothermic process is one that absorbs heat from the surroundings. 17.1

11 Slide 11 of 34 © Copyright Pearson Prentice Hall > The Flow of Energy—Heat and Work Exothermic and Endothermic Processes An exothermic process is one that releases heat to its surroundings. 17.1

12 © Copyright Pearson Prentice Hall Slide 12 of 34 Conceptual Problem 17.1

13 © Copyright Pearson Prentice Hall Slide 13 of 34 Conceptual Problem 17.1

14 © Copyright Pearson Prentice Hall Slide 14 of 34 Conceptuall Problem 17.1

15 © Copyright Pearson Prentice Hall Slide 15 of 34 Practice Problems for Conceptual Problem 17.1 Problem Solving 17.1 Solve Problem 1 with the help of an interactive guided tutorial.

16 © Copyright Pearson Prentice Hall The Flow of Energy—Heat and Work > Slide 16 of 34 Units for Measuring Heat Flow In what units is heat flow measured? 17.1

17 Slide 17 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

18 © Copyright Pearson Prentice Hall The Flow of Energy—Heat and Work > Slide 18 of 34 Heat Capacity and Specific Heat On what two factors does the heat capacity of an object depend? 17.1

19 Slide 19 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

20 Slide 20 of 34 © Copyright Pearson Prentice Hall > 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. 17.1

21 Slide 21 of 34 © Copyright Pearson Prentice Hall > The Flow of Energy—Heat and Work Heat Capacity and Specific Heat Water releases a lot of heat as it cools. During freezing weather, farmers protect citrus crops by spraying them with water. 17.1

22 Slide 22 of 34 © Copyright Pearson Prentice Hall > The Flow of Energy—Heat and Work Heat Capacity and Specific Heat 17.1

23 Slide 23 of 34 © Copyright Pearson Prentice Hall > 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 tongue than the crust. 17.1

24 © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 24 of

25 © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 25 of

26 © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 26 of

27 © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 27 of

28 © Copyright Pearson Prentice Hall Slide 28 of 34 Practice Problems for Sample Problem 17.1 Problem Solving 17.4 Solve Problem 4 with the help of an interactive guided tutorial.

29 © Copyright Pearson Prentice Hall Slide 29 of 34 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 17.1 Section Quiz. 17.1

30 © Copyright Pearson Prentice Hall Slide 30 of 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 Section Quiz.

31 © Copyright Pearson Prentice Hall Slide 31 of 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 Section Quiz.

32 © Copyright Pearson Prentice Hall Slide 32 of 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 Section Quiz.

33 © Copyright Pearson Prentice Hall Slide 33 of Which of the relationships listed below can be used to convert between the two units used to measure heat transfer? a.1 g = 1 º C b.1 J = cal c.1 º C = 1 cal d.1 g = J 17.1 Section Quiz.

34 © Copyright Pearson Prentice Hall Slide 34 of 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 Section Quiz.

35 END OF SHOW


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