1. Chemistry 13.1

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3. Kinetic Theory and a Model for Gases
13.1
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.

4. Kinetic Theory and a Model for Gases
13.1
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.

5. Kinetic Theory and a Model for Gases
13.1
Kinetic Theory and a Model for Gases
Particles in a gas are in rapid, constant motion.
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.

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

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

8. An empty space with no particles and no pressure is called a vacuum.
13.1
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.

9. 13.1
Gas Pressure
Gas pressure is the result of simultaneous collisions of billions of rapidly moving particles in a gas with an object.

10. A barometer is a device that is used to measure atmospheric pressure.
13.1
Gas Pressure
A barometer is a device that is used to measure atmospheric pressure.
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?

11. The SI unit of pressure is the pascal (Pa).
13.1
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.

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13. 13.1

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

17. Kinetic Energy and Temperature
13.1
Kinetic Energy and Temperature
Kinetic Energy and Temperature
What is the relationship between the temperature in kelvins and the average kinetic energy of particles?

18. Kinetic Energy and Temperature
13.1
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.

19. Kinetic Energy and Temperature
13.1
Kinetic Energy and Temperature
The red and blue curves show the kinetic energy distributions of a typical collection of molecules at two different temperatures. INTERPRETING GRAPHS a. Inferring Which point on each curve represents the average kinetic energy? b. Analyzing Data Compare the shapes of the curves for cold water and hot water. c. Predicting What would happen to the shape of the curve if the water temperature were even higher? Even lower?

20. Kinetic Energy and Temperature
13.1
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.

21. Kinetic Energy and Temperature
13.1
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.
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.

22. Kinetic Energy and Temperature
13.1
Kinetic Energy and Temperature
In this vacuum chamber, scientists cooled sodium vapor to nearly absolute zero.
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.

23. 13.1 Section Quiz.
13.1.

24. 13.1 Section Quiz.
1. According to the kinetic theory, the particles in a gas
are attracted to each other.
are in constant random motion.
have the same kinetic energy.
have a significant volume.

25. 13.1 Section Quiz.
2. The pressure a gas exerts on another object is caused by
the physical size of the gas particles.
collisions between gas particles and the object.
collisions between gas particles.
the chemical composition of the gas.

26. 13.1 Section Quiz.
3. The average kinetic energy of the particles in a substance is directly proportional to the
Fahrenheit temperature.
Kelvin temperature.
molar mass of the substance.
Celsius temperature.

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