1. Chapter 10 Energy

2. Section 10.1 The Nature of Energy Return to TOC Copyright © Cengage Learning. All rights reserved 2 Energy is anything that has the ability to do work or produce heat.  All chemical and physical changes result in the matter changing energy. Energy

3. Section 10.1 The Nature of Energy Return to TOC Copyright © Cengage Learning. All rights reserved 3 Potential energy – stored energy, due to position or composition. Kinetic energy – energy of motion, energy that is being transferred from one object to another. Energy

4. Section 10.1 The Nature of Energy Return to TOC Copyright © Cengage Learning. All rights reserved 4 Energy can be converted from one form to another, but can be neither created nor destroyed.  The energy of the universe is constant—first law of thermodynamics. Law of Conservation of Energy

5. Section 10.1 The Nature of Energy Return to TOC Copyright © Cengage Learning. All rights reserved 5 Energy

6. Section 10.2 Temperature and Heat Return to TOC Copyright © Cengage Learning. All rights reserved 6 A measure of the random motions of the components of a substance. Temperature

7. Section 10.2 Temperature and Heat Return to TOC Copyright © Cengage Learning. All rights reserved 7 A flow of energy between two objects due to a temperature difference between the objects. Heat

8. Section 10.3 Exothermic and Endothermic Processes Return to TOC Copyright © Cengage Learning. All rights reserved 8 System – part of the universe on which we wish to focus attention. Surroundings – include everything else in the universe.

9. Section 10.3 Exothermic and Endothermic Processes Return to TOC Copyright © Cengage Learning. All rights reserved 9 Endothermic Process:  Heat flows into a system.  Absorb energy from the surroundings. Surroundings reaction

10. Section 10.3 Exothermic and Endothermic Processes Return to TOC Copyright © Cengage Learning. All rights reserved 10 Exothermic Process:  Energy flows out of the system.  Energy gained by the surroundings is equal to the energy lost by the system. Surroundings reaction

11. Section 10.3 Exothermic and Endothermic Processes Return to TOC Copyright © Cengage Learning. All rights reserved 11 Changes in State

12. Section 10.3 Exothermic and Endothermic Processes Return to TOC Copyright © Cengage Learning. All rights reserved 12 Concept Check Classify each process as exothermic or endothermic. Explain. The system is underlined in each example. a)Your hand gets cold when you touch ice. b)The ice gets warmer when you touch it. c)Water boils in a kettle being heated on a stove. d)Water vapor condenses on a cold pipe. e)Ice cream melts.

13. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 13 The common energy units for heat are the calorie and the joule.  calorie (cal) – the amount of energy (heat) required to raise the temperature of one gram of water 1 o C.  Joule (J) – 1 calorie = 4.184 joules

14. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 14 1.The amount of substance being heated (number of grams). 2.The temperature change (number of degrees). 3.The identity of the substance. Energy (Heat) Required to Change the Temperature of a Substance Depends On:

15. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 15 Heat capacity is the amount of heat a substance must absorb to raise its temperature by 1 °C. Specific heat = heat capacity of 1 gram of the substance. Specific Heat Capacity

16. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 16 Specific Heat Capacities of Some Common Substances

17. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 17 Energy (heat) required, Q = s × m × ΔT Q = energy (heat) required (J) s = specific heat capacity (J/°C·g) m = mass (g) ΔT = change in temperature (°C) Energy Required for a Reaction or Process:

18. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 18 Calculate the amount of heat energy (in joules) needed to raise the temperature of 6.25 g of water from 21.0°C to 39.0°C. Example

19. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 19 Exercises 1.A sample of pure iron requires 142 cal of energy to raise its temperature from 23ºC to 92ºC. What is the mass of the sample? (The specific heat capacity of iron is 0.45 J/gºC.) 2.A 100.0 g sample of water at 90.°C is added to a 500.0 g sample of water at 10.°C. Calculate the final temperature of the water.

20. Section 10.5 Measuring Energy Changes Return to TOC Copyright © Cengage Learning. All rights reserved 20 Summary of Topics: Chapter 10 Energy Endothermic, exothermic –Phase changes Heat Capacity