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.
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Compressibility Why are gases easier to compress than solids or
liquids are?
Slide 4
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.
Slide 5
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.
Slide 6
At room temperature, the distance between particles in an
enclosed gas is about 10 times the diameter of a particle.
Slide 7
Factors Affecting Gas Pressure What are the three factors that
affect gas pressure?
Slide 8
The amount of gas, volume, and temperature are factors that
affect gas pressure.
Slide 9
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.
Slide 10
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.
Slide 11
If the gas pressure increases until it exceeds the strength of
an enclosed, rigid container, the container will burst.
Slide 12
Aerosol Spray Paint
Slide 13
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.
Slide 14
When the volume of the container is halved, the pressure the
gas exerts is doubled.
Slide 15
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.
Slide 16
When the Kelvin temperature of the enclosed gas doubles, the
pressure of the enclosed gas doubles.
Slide 17
This hot air balloon was designed to carry a passenger around
the world. You will study some laws that will allow you to predict
gas behavior under specific conditions, such as in a hot air
balloon.
Slide 18
Boyles Law: Pressure and Volume How are the pressure, volume,
and temperature of a gas related?
Slide 19
If the temperature is constant, as the pressure of a gas
increases, the volume decreases.
Slide 20
Boyles law states that for a given mass of gas at constant
temperature, the volume of the gas varies inversely with
pressure.
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Charless Law: Temperature and Volume As the temperature of an
enclosed gas increases, the volume increases, if the pressure is
constant.
Slide 25
As the temperature of the water increases, the volume of the
balloon increases.
Slide 26
Charless law states that the volume of a fixed mass of gas is
directly proportional to its Kelvin temperature if the pressure is
kept constant.
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Gay-Lussacs Law: Pressure and Temperature As the temperature of
an enclosed gas increases, the pressure increases, if the volume is
constant.
Slide 31
When a gas is heated at constant volume, the pressure
increases.
Slide 32
Gay-Lussacs law states that the pressure of a gas is directly
proportional to the Kelvin temperature if the volume remains
constant.
Slide 33
A pressure cooker demonstrates Gay-Lussacs Law.
Slide 34
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Weather balloons carry data- gathering instruments high into
Earths atmosphere. At an altitude of about 27,000 meters, the
balloon bursts.
Slide 37
The Combined Gas Law When is the combined gas law used to solve
problems?
Slide 38
The combined gas law describes the relationship among the
pressure, temperature, and volume of an enclosed gas.
Slide 39
The combined gas law allows you to do calculations for
situations in which only the amount of gas is constant. Reference
Table T
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Solid carbon dioxide, or dry ice, doesnt melt. It sublimes. Dry
ice can exist because gases dont 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.
Slide 43
Ideal Gas Law What is needed to calculate the amount of gas in
a sample at given conditions of volume, temperature, and
pressure?
Slide 44
To calculate the number of moles of a contained gas requires an
expression that contains the variable n.
Slide 45
The gas law that includes all four variables P, V, T, and nis
called the ideal gas law. The ideal gas constant (R) has the value
8.31 (LkPa)/(Kmol).
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Ideal Gases and Real Gases Under what conditions are real gases
most likely to differ from ideal gases?
Slide 49
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.
Slide 50
Real gases differ most from an ideal gas at low temperatures
and high pressures. Small gases behave most ideally (H 2 & He).
Large gases deviate the most.
Slide 51
Slide 52
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.
Slide 53
Daltons Law How is the total pressure of a mixture of gases
related to the partial pressures of the component gases?
Slide 54
The contribution each gas in a mixture makes to the total
pressure is called the partial pressure exerted by that gas.
Slide 55
In a mixture of gases, the total pressure is the sum of the
partial pressures of the gases.
Slide 56
Daltons 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.
Slide 57
Three gases are combined in container T.
Slide 58
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.
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Grahams Law How does the molar mass of a gas affect the rate at
which the gas effuses or diffuses?
Slide 62
Diffusion is the tendency of molecules to move toward areas of
lower concentration until the concentration is uniform
throughout.
Slide 63
Bromine vapor is diffusing upward through the air in a
graduated cylinder.
Slide 64
After several hours, the bromine has diffused almost to the top
of the cylinder.
Slide 65
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.
Slide 66
Thomas Grahams Contribution Grahams law of effusion states that
the rate of effusion of a gas is inversely proportional to the
square root of the gass molar mass. This law can also be applied to
the diffusion of gases.
Slide 67
Comparing Effusion Rates A helium filled balloon will deflate
sooner than an air- filled balloon.
Slide 68
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.
Slide 69
Because the rate of effusion is related only to a particles
speed, Grahams law can be written as follows for two gases, A and
B.
Slide 70
Helium effuses (and diffuses) nearly three times faster than
nitrogen at the same temperature.