Chapter 17 Notes - PC\|MAC
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4/10/14 1 Slide 1 of 34 © Copyright Pearson Prentice Hall > The Flow of Energy—Heat and Work Energy Transformations Heat (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 Slide 2 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 Slide 3 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
Transcript of Chapter 17 Notes - PC\|MAC
4/10/14
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Slide 1 of 34
© Copyright Pearson Prentice Hall
>The Flow of Energy—Heat and Work Energy Transformations
Heat (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
Slide 2 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.
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© 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
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>The Flow of Energy—Heat and Work Exothermic and Endothermic Processes
The law of conservation of energy states that in any chemical or physical process, energy is neither created nor destroyed.
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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.
17.1
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Practice Problems for Conceptual Problem 17.1
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Practice Problems
Heat flows from the system (parafin) to the surroundings (air). The process is exothermic.
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>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.
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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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>The Flow of Energy—Heat and Work Heat Capacity and Specific Heat
The amount of heat needed to increase the temperature of an object exactly 1°C is the heat capacity of that object.
The heat capacity of an object depends on both its mass and its chemical composition.
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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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SAMPLE PROBLEM
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© 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.
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Slide 17 of 34
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>The Flow of Energy—Heat and Work Calorimetry
Calorimetry - the precise measurement of the heat flow into or out of a system for chemical and physical processes.
17.2
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>The Flow of Energy—Heat and Work Calorimetry
In Calorimetry:
heat released by system = heat absorbed by surroundings
Conversely:
heat absorbed by system = heat released by surroundings
17.2
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>The Flow of Energy—Heat and Work Calorimetry
Enthalpy (H) - the heat content of a system at constant pressure.
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SAMPLE PROBLEM
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>The Flow of Energy—Heat and Work Thermochemical Equations
Thermochemical Equation – a chemical equation that includes the enthalpy change.
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>The Flow of Energy—Heat and Work Thermochemical Equations
Heat of reaction - the enthalpy change for the chemical equation exactly as it is written.
17.2
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>The Flow of Energy—Heat and Work Thermochemical Equations
Heat of combustion - the heat of reaction for the complete burning of one mole of a substance.
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SAMPLE PROBLEM
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SAMPLE PROBLEM
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17.3
