1. Slide 1 of 29 Chemistry 13.1

2. © Copyright Pearson Prentice Hall Slide 2 of 29 The Nature of Gases The skunk releases its spray! Within seconds you smell that all-too-familiar foul odor. You will discover some general characteristics of gases that help explain how odors travel through the air, even on a windless day. 13.1

3. © Copyright Pearson Prentice Hall The Nature of Gases > Slide 3 of 29 Kinetic Theory and a Model for Gases What are the three assumptions of the kinetic theory as it applies to gases? 13.1

4. Slide 4 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Theory and a Model for Gases The word kinetic refers to motion. The energy an object has because of its motion is called kinetic energy. According to the kinetic theory, all matter consists of tiny particles that are in constant motion. 13.1

5. Slide 5 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Theory and a Model for Gases According to kinetic theory: The particles in a gas are considered to be small, hard spheres with an insignificant volume. The motion of the particles in a gas is rapid, constant, and random. All collisions between particles in a gas are perfectly elastic. 13.1

6. Slide 6 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Theory and a Model for Gases Particles in a gas are in rapid, constant motion. 13.1

7. Slide 7 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Theory and a Model for Gases Gas particles travel in straight-line paths. 13.1

8. Slide 8 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Theory and a Model for Gases The gas fills the container. 13.1

9. © Copyright Pearson Prentice Hall The Nature of Gases > Slide 9 of 29 Gas Pressure How does kinetic theory explain gas pressure? 13.1

10. Slide 10 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Gas Pressure Gas pressure results from the force exerted by a gas per unit surface area of an object. An empty space with no particles and no pressure is called a vacuum. Atmospheric pressure results from the collisions of atoms and molecules in air with objects. 13.1

11. © Copyright Pearson Prentice Hall Slide 11 of 29 > The Nature of Gases Gas Pressure Gas pressure is the result of simultaneous collisions of billions of rapidly moving particles in a gas with an object. 13.1

12. Slide 12 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Gas Pressure A barometer is a device that is used to measure atmospheric pressure. 13.1

13. Slide 13 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Gas Pressure The SI unit of pressure is the pascal (Pa). One standard atmosphere (atm) is the pressure required to support 760 mm of mercury in a mercury barometer at 25°C. 13.1

14. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 14 of 29 13.1

15. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 15 of 29 13.1

16. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 16 of 29 13.1

17. © Copyright Pearson Prentice Hall SAMPLE PROBLEM Slide 17 of 29 13.1

18. © Copyright Pearson Prentice Hall Slide 18 of 29 Practice Problems for Sample Problem 13.1 Problem Solving 13.1 Solve Problem 1 with the help of an interactive guided tutorial.

19. © Copyright Pearson Prentice Hall The Nature of Gases > Slide 19 of 29 Kinetic Energy and Temperature What is the relationship between the temperature in kelvins and the average kinetic energy of particles? 13.1

20. Slide 20 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Energy and Temperature Average Kinetic Energy The particles in any collection of atoms or molecules at a given temperature have a wide range of kinetic energies. Most of the particles have kinetic energies somewhere in the middle of this range. 13.1

21. Slide 21 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Energy and Temperature 13.1

22. Slide 22 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Energy and Temperature Absolute zero (0 K, or –273.15°C) is the temperature at which the motion of particles theoretically ceases. Particles would have no kinetic energy at absolute zero. Absolute zero has never been produced in the laboratory. 13.1

23. Slide 23 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Energy and Temperature Average Kinetic Energy and Kelvin Temperature The Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance. 13.1

24. Slide 24 of 29 © Copyright Pearson Prentice Hall > The Nature of Gases Kinetic Energy and Temperature In this vacuum chamber, scientists cooled sodium vapor to nearly absolute zero. 13.1

25. © Copyright Pearson Prentice Hall The Nature of Gases > Slide 25 of 29 Kinetic Energy and Temperature Animation 14 Observe particles in motion and discover the connection between temperature and kinetic energy.

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