Transcript chapter 14 powerpoint part I of II

14.1
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.
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14.1
Properties of Gases > 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.
Why are gases easier
to compress than
solids or liquids are?
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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.
• At room temperature, the distance
between particles in an enclosed gas is
about 10 times the diameter of a
particle.
14.1
Properties of Gases > Factors Affecting Gas Pressure
Factors Affecting Gas Pressure
What are the three factors that affect gas
pressure?
The amount of gas, volume, and
temperature are factors that affect gas
pressure.
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14.1
Properties of Gases > Factors Affecting 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).
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14.1
Properties of Gases > 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.
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14.1
Properties of Gases > 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.
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14.1
Properties of Gases > Factors Affecting Gas Pressure
If the gas pressure increases until it exceeds the
strength of an enclosed, rigid container, the
container will burst.
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14.1
Properties of Gases > 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.
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14.1
Properties of Gases > Factors Affecting Gas Pressure
When the volume of the container is halved, the
pressure the gas exerts is doubled.
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14.1
Properties of Gases > 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.
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14.1
Properties of Gases > Factors Affecting Gas Pressure
When the Kelvin temperature of the enclosed
gas doubles, the pressure of the enclosed gas
doubles.
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14.1 Section Quiz.
Assess students’ understanding
of the concepts in Section 14.1.
Continue to:
-or-
Launch:
Section Quiz
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14.1 Section Quiz.
1. Compared to liquids and solids, gases are
easily compressed because the particles in a
gas
a. attract each other.
b. are spaced relatively far apart.
c. are very small.
d. repel each other.
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14.1 Section Quiz.
2. Gas pressure is affected by
a. temperature, volume, and the amount of
the gas.
b. temperature, volume, and the molar mass
of the gas.
c. phase diagram, volume, and the size of the
container.
d. temperature, phase diagram, and the mass
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of the gas container.
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14.1 Section Quiz.
3. For gases, the SI units for volume (V),
pressure (P), and temperature (T) are,
respectively,
a. liters, kilopascals, and °C.
b. liters, kilopascals, and kelvins.
c. cm3, kilopascals, and kelvins.
d. liters, atmospheres, and °C.
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The Gas Laws
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.
How are the pressure, volume, and
temperature of a fixed quantity of gas
related?
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Boyle’s Law: Pressure and Volume
If the temperature is constant, as the
pressure of a gas increases, the volume
decreases.
Boyle’s 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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Boyle’s Law: Pressure and Volume
Simulation (Virtual lab) and Boyle’ Law Lab
Examine the relationship between gas volume and
pressure.
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14.1
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14.1
for INDEX
SampleCARD
Problem
14.1 (turn in for evaluation)
activity
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 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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Charles’s Law: Temperature and Volume
As the temperature of the water increases, the
volume of the balloon increases.
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Charles’s Law: Temperature and Volume
Simulation (Virtual Lab): Examine the relationship
between gas volume and temperature.
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14.2
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14.2
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for INDEX
SampleCARD
Problem
14.2 (turn in for evaluation)
activity
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 states that the pressure of a gas is
directly proportional to the Kelvin temperature if the
volume remains constant.
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Gay-Lussac’s Law: Pressure and Temperature
When a gas is heated at constant volume, the
pressure increases.
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Gay-Lussac’s Law: Pressure and Temperature
A pressure cooker demonstrates Gay-Lussac’s Law.
Simulation (virtual lab)
Examine the relationship
between gas pressure and
temperature.
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14.3
14.3
for INDEX
SampleCARD
Problem
14.3 (turn in for evaluation)
activity
The Combined Gas Law
The combined gas law describes the relationship
among the pressure, temperature, and volume of
an enclosed gas.
The combined gas law allows you to do calculations
for situations in which only the amount of gas is
constant.
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14.4
14.4
for Sample Problem 14.4
INDEX CARD activity (turn in for evaluation)
The Combined Gas Law
Weather balloons carry
data-gathering
instruments high
into Earth’s
atmosphere. At an
altitude of about
27,000 meters, the
balloon bursts.
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14.2 Section Quiz.
1. If the volume of a gas in a container were
reduced to one fifth the original volume at
constant temperature, the pressure of the gas
in the new volume would be
a. one and one fifth times the original
pressure.
b. one fifth of the original pressure.
c. four fifths of the original pressure.
d. five times the original pressure.
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14.2 Section Quiz.
2. A balloon appears slightly smaller when it is
moved from the mountains to the seashore at
constant temperature. The best gas law to
explain this observation would be
a. Gay-Lussacs's Law.
b. Graham's Law.
c. Boyle's Law.
d. Charles's Law.
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14.2 Section Quiz.
3. At 46°C and 89 kPa pressure, a gas occupies
a volume of 0.600 L. How many liters will it
occupy at 0°C and 20.8 kPa?
a. 0.600 L
b. 2.58 L
c. 0.140 L
d. 2.20 L
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