1. Chemistry 13.1

2. The Nature of Gases
13.1
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.

3. Kinetic Theory and a Model for Gases
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Kinetic Theory and a Model for Gases
Kinetic Theory and a Model for Gases
What are the three assumptions of the kinetic theory as it applies to gases?
At sea level, air exerts enough pressure to support a 760-mm column of mercury. On top of Mount Everest, at 9000 m, the air exerts only enough pressure to support a 253-mm column of mercury. Calculating What is the decrease in pressure from sea level to the top of Mount Everest?

4. Kinetic Theory and a Model for Gases
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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.

5. Kinetic Theory and a Model for Gases
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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.

6. Kinetic Theory and a Model for Gases
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Kinetic Theory and a Model for Gases
Particles in a gas are in rapid, constant motion.

7. Kinetic Theory and a Model for Gases
13.1
Kinetic Theory and a Model for Gases
Gas particles travel in straight-line paths.

8. Kinetic Theory and a Model for Gases
13.1
Kinetic Theory and a Model for Gases
The gas fills the container.

9. Gas Pressure How does kinetic theory explain gas pressure? 13.1

10. An empty space with no particles and no pressure is called a vacuum.
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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.

11. 13.1
Gas Pressure
Gas pressure is the result of simultaneous collisions of billions of rapidly moving particles in a gas with an object.
In this vacuum chamber, scientists cooled sodium vapor to nearly absolute zero. To keep the atoms from sticking to the walls of the chamber, the scientists used magnetism and gravity to trap the atoms 0.5 cm above the coil in the center of the chamber. The coil is shown at about two times its actual size.

12. A barometer is a device that is used to measure atmospheric pressure.
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Gas Pressure
A barometer is a device that is used to measure atmospheric pressure.

13. The SI unit of pressure is the pascal (Pa).
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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.
In this vacuum chamber, scientists cooled sodium vapor to nearly absolute zero. To keep the atoms from sticking to the walls of the chamber, the scientists used magnetism and gravity to trap the atoms 0.5 cm above the coil in the center of the chamber. The coil is shown at about two times its actual size.

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17. 13.1

18. for Sample Problem 13.1
Problem Solving 13.1 Solve Problem 1 with the help of an interactive guided tutorial.

19. Kinetic Energy and Temperature
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Kinetic Energy and Temperature
Kinetic Energy and Temperature
What is the relationship between the temperature in kelvins and the average kinetic energy of particles?

20. Kinetic Energy and Temperature
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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.

21. Kinetic Energy and Temperature
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Kinetic Energy and Temperature

22. Kinetic Energy and Temperature
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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.
Gases share some general characteristics. a) The rapid, constant motion of particles in a gas causes them to collide with one another and with the walls of their container. b) The particles travel in straight-line paths between collisions. c) A gas fills all the available space in its container.

23. Kinetic Energy and Temperature
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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.
Gases share some general characteristics. a) The rapid, constant motion of particles in a gas causes them to collide with one another and with the walls of their container. b) The particles travel in straight-line paths between collisions. c) A gas fills all the available space in its container.