Chapter 14
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Chapter 14. Gases. 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. . 13.1. 13.1. 13.1. for Sample Problem 13.1. Properties of Gases.

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Chapter 14

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Chapter 14

Chapter 14

Gases


Gas pressure

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.


Chapter 14

13.1


Chapter 14

13.1


Chapter 14

13.1


For sample problem 13 1

for Sample Problem 13.1


Properties of gases

Properties of Gases

  • In organized soccer, a ball that is properly inflated will rebound faster and travel farther than a ball that is under-inflated. If the pressure is too high, the ball may burst when it is kicked. You will study variables that affect the pressure of a gas.


Compressibility

Compressibility

  • Compressibility

    • Why are gases easier to compress than solids or liquids are?


Compressibility1

Compressibility

  • Compressibility is a measure of how much the volume of matter decreases under pressure. When a person collides with an inflated airbag, the compression of the gas absorbs the energy of the impact.


Compressibility2

Compressibility

  • Gases are easily compressed because of the space between the particles in a gas.

    • The distance between particles in a gas is much greater than the distance between particles in a liquid or solid.

    • Under pressure, the particles in a gas are forced closer together.


Compressibility3

Compressibility

  • At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle.


Factors affecting gas pressure

Factors Affecting Gas Pressure

  • Factors Affecting Gas Pressure

    • What are the three factors that affect gas pressure?


Factors affecting gas pressure1

Factors Affecting Gas Pressure

  • The amount of gas, volume, and temperature are factors that affect gas pressure.

    • Four variables are generally used to describe a gas. The variables and their common units are

      • pressure (P) in kilopascals

      • volume (V) in liters

      • temperature (T) in kelvins

      • the number of moles (n).


Factors affecting gas pressure2

Factors Affecting Gas Pressure

  • Amount of Gas

    • You can use kinetic theory to predict and explain how gases will respond to a change of conditions. If you inflate an air raft, for example, the pressure inside the raft will increase.


Factors affecting gas pressure3

Factors Affecting Gas Pressure

  • Collisions of particles with the inside walls of the raft result in the pressure that is exerted by the enclosed gas. Increasing the number of particles increases the number of collisions, which is why the gas pressure increases.


Factors affecting gas pressure4

Factors Affecting Gas Pressure

  • If the gas pressure increases until it exceeds the strength of an enclosed, rigid container, the container will burst.


Factors affecting gas pressure5

Factors Affecting Gas Pressure

  • Aerosol Spray Paint


Factors affecting gas pressure6

Factors Affecting Gas Pressure

  • Volume

    • You can raise the pressure exerted by a contained gas by reducing its volume. The more a gas is compressed, the greater is the pressure that the gas exerts inside the container.


Factors affecting gas pressure7

Factors Affecting Gas Pressure

  • When the volume of the container is halved, the pressure the gas exerts is doubled.


Factors affecting gas pressure8

Factors Affecting Gas Pressure

  • Temperature

    • An increase in the temperature of an enclosed gas causes an increase in its pressure.

    • As a gas is heated, the average kinetic energy of the particles in the gas increases. Faster-moving particles strike the walls of their container with more energy.


Web links gas laws demonstrations

Web Links: Gas Laws Demonstrations

  • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/gasesv6.swf

  • http://intro.chem.okstate.edu/1314F00/Laboratory/GLP.htm


14 2 gas laws

14.2 Gas Laws


Boyle s law pressure and volume

Boyle’s Law: Pressure and Volume

  • Boyle’s Law: Pressure and Volume

    • How are the pressure, volume, and temperature of a gas related?


Boyle s law pressure and volume1

Boyle’s Law: Pressure and Volume

  • If the temperature is constant, as the pressure of a gas increases, the volume decreases.


Boyle s law pressure and volume2

Boyle’s Law: Pressure and Volume

  • Boyle’s law states that for a given mass of gas at constant temperature, the volume of the gas varies inversely with pressure.


Boyle s law pressure and volume3

Boyle’s Law: Pressure and Volume


Chapter 14

14.1


Chapter 14

14.1


Chapter 14

14.1


For sample problem 14 1

for Sample Problem 14.1


Charles s law temperature and volume

Charles’s Law: Temperature and Volume

  • Charles’s Law: Temperature and Volume

    • As the temperature of an enclosed gas increases, the volume increases, if the pressure is constant.


Charles s law temperature and volume1

Charles’s Law: Temperature and Volume

  • As the temperature of the water increases, the volume of the balloon increases.


Charles s law temperature and volume2

Charles’s Law: Temperature and Volume

  • Charles’s law states that the volume of a fixed mass of gas is directly proportional to its Kelvin temperature if the pressure is kept constant.


Charles s law temperature and volume3

Charles’s Law: Temperature and Volume


Chapter 14

14.2


Chapter 14

14.2


Chapter 14

14.2


For sample problem 14 2

for Sample Problem 14.2


Gay lussac s law pressure and temperature

Gay-Lussac’s Law: Pressure and Temperature

  • Gay-Lussac’s Law: Pressure and Temperature

    • As the temperature of an enclosed gas increases, the pressure increases, if the volume is constant.


Gay lussac s law pressure and temperature1

Gay-Lussac’s Law: Pressure and Temperature

  • When a gas is heated at constant volume, the pressure increases.


Gay lussac s law pressure and temperature2

Gay-Lussac’s Law: Pressure and Temperature

  • Gay-Lussac’s law states that the pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constant.


Gay lussac s law pressure and temperature3

Gay-Lussac’s Law: Pressure and Temperature

  • A pressure cooker demonstrates Gay-Lussac’s Law.


Chapter 14

14.3


Chapter 14

14.3


Chapter 14

14.3


For sample problem 14 3

for Sample Problem 14.3


The combined gas law

The Combined Gas Law

  • The Combined Gas Law

    • When is the combined gas law used to solve problems?


The combined gas law1

The Combined Gas Law

  • The combined gas law describes the relationship among the pressure, temperature, and volume of an enclosed gas.


The combined gas law2

The Combined Gas Law

  • The combined gas law allows you to do calculations for situations in which only the amount of gas is constant.


Chapter 14

14.4


Chapter 14

14.4


Chapter 14

14.4


For sample problem 14 4

for Sample Problem 14.4


14 3 ideal gas law

14.3 Ideal Gas Law


Ideal gases

Ideal Gases

  • Solid carbon dioxide, or dry ice, doesn’t melt. It sublimes. Dry ice can exist because gases don’t obey the assumptions of kinetic theory under all conditions. You will learn how real gases differ from the ideal gases on which the gas laws are based.


Ideal gas law

Ideal Gas Law

  • Ideal Gas Law

    • What is needed to calculate the amount of gas in a sample at given conditions of volume, temperature, and pressure?


Ideal gas law1

Ideal Gas Law

  • To calculate the number of moles of a contained gas requires an expression that contains the variable n.


Ideal gas law2

Ideal Gas Law

  • The gas law that includes all four variables—P, V, T, and n—is called the ideal gas law.

  • The ideal gas constant (R) has the value 8.31 (L·kPa)/(K·mol).


Chapter 14

14.5


Chapter 14

14.5


Chapter 14

14.5


Chapter 14

14.5


For sample problem 14 5

for Sample Problem 14.5


Ideal gases and real gases

Ideal Gases and Real Gases

  • Ideal Gases and Real Gases

    • Under what conditions are real gases most likely to differ from ideal gases?


Ideal gases and real gases1

Ideal Gases and Real Gases

  • There are attractions between the particles in an ideal gas. Because of these attractions, a gas can condense,or even solidify, when it is compressed or cooled.


Ideal gases and real gases2

Ideal Gases and Real Gases

  • Real gases differ most from an ideal gas at low temperatures and high pressures.


Ideal gases and real gases3

Ideal Gases and Real Gases


Chapter 14

14.4


Gases mixtures and movements

Gases: Mixtures and Movements

  • A list of gear for an expedition to Mount Everest includes climbing equipment, ski goggles, a down parka with a hood, and most importantly compressed-gas cylinders of oxygen. You will find out why a supply of oxygen is essential at higher altitudes.


Dalton s law

Dalton’s Law

  • Dalton’s Law

    • How is the total pressure of a mixture of gases related to the partial pressures of the component gases?


Dalton s law1

Dalton’s Law

  • The contribution each gas in a mixture makes to the total pressure is called the partial pressure exerted by that gas.


Dalton s law2

Dalton’s Law

  • In a mixture of gases, the total pressure is the sum of the partial pressures of the gases.


Dalton s law3

Dalton’s Law

  • Dalton’s law of partial pressures states that, at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases.


Dalton s law4

Dalton’s Law

  • Three gases are combined in container T.


Dalton s law5

Dalton’s Law

  • The partial pressure of oxygen must be 10.67 kPa or higher to support respiration in humans. The climber below needs an oxygen mask and a cylinder of compressed oxygen to survive.


Chapter 14

14.6


Chapter 14

14.6


Chapter 14

14.6


Chapter 14

14.6


For sample problem 14 6

for Sample Problem 14.6


Graham s law

Graham’s Law

  • Graham’s Law

    • How does the molar mass of a gas affect the rate at which the gas effuses or diffuses?


Graham s law1

Graham’s Law

  • Diffusion is the tendency of molecules to move from areas of high concentration toward areas of lower concentration until the concentration is uniform throughout.


Graham s law2

Graham’s Law

  • Bromine vapor is diffusing upward through the air in a graduated cylinder.


Graham s law3

Graham’s Law

  • After several hours, the bromine has diffused almost to the top of the cylinder.


Graham s law4

Graham’s Law

  • During effusion, a gas escapes through a tiny hole in its container.

    • Gases of lower molar mass diffuse and effuse faster than gases of higher molar mass.


Graham s law5

Graham’s Law

  • Thomas Graham’s Contribution

    • Graham’slaw of effusion states that the rate of effusion of a gas is inversely proportional to the square root of the gas’s molar mass. This law can also be applied to the diffusion of gases.


Graham s law6

Graham’s Law

  • Comparing Effusion Rates

    • A helium filled balloon will deflate sooner than an air-filled balloon.


Graham s law7

Graham’s Law

  • Helium atoms are less massive than oxygen or nitrogen molecules. So the molecules in air move more slowly than helium atoms with the same kinetic energy.


Graham s law8

Graham’s Law

  • Because the rate of effusion is related only to a particle’s speed, Graham’s law can be written as follows for two gases, A and B.


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