Chapter 14: Gas Laws: Pressure, Volume, and Temperature

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Chapter 14 Gas Laws Pressure, Volume, and
Temperature
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Basic Terminology

• Review of terms used to describe the properties
  and behavior of gases.

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Opening thoughts

• Have you ever

Had a soda bottle spray all over you?
Baked (or eaten) a nice, fluffy cake?
These are all examples of gases at work!
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Properties of Gases

• You can predict the behavior of gases based on
  the following properties

Pressure
Volume
Amount (moles)
Temperature
Lets review each of these briefly
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• You can predict the behavior of gases based on
  the following properties

Pressure
Volume
Amount (moles)
Temperature
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Pressure
Pressure is defined as the force the gas exerts
on a given area of the container in which it is
contained. The SI unit for pressure is the
Pascal, Pa.

• If youve ever inflated a tire, youve probably
  made a pressure measurement in pounds (force) per
  square inch (area).

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• You can predict the behavior of gases based on
  the following properties

Pressure
Volume
Amount (moles)
Temperature
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Volume
Volume is the three-dimensional space inside the
container holding the gas. The SI unit for
volume is the cubic meter, m3. A more common and
convenient unit is the liter, L.
Think of a 2-liter bottle of soda to get an idea
of how big a liter is.
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• You can predict the behavior of gases based on
  the following properties

Pressure
Volume
Amount (moles)
Temperature
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Amount (moles)
Amount of substance is tricky. As weve already
learned, the SI unit for amount of substance is
the mole, mol. Since we cant count molecules,
we can convert measured mass to the number of
moles, n, using the molar mass.
By definition, one mole of a substance contains
approximately 6.022 x 1023 particles of the
substance. You can understand why we use mass
and moles!
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• You can predict the behavior of gases based on
  the following properties

Pressure
Volume
Amount (moles)
Temperature
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Temperature
Temperature is the measurement of heator how
fast the particles are moving. Gases, at room
temperature, have a lower boiling point than
things that are liquid or solid at the same
temperature. Remember Not all substance freeze,
melt or evaporate at the same temperature.
Water will freeze at zero degrees Celsius.
However Alcohol will not freeze at this
temperature.
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How do they all relate?

• Some relationships of gases may be easy to
  predict. Some are more subtle.Now that we
  understand the factors that affect the behavior
  of gases, we will study how those factors
  interact.

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Boyles Law

• Boyles Law, describes the relationship between
  pressure and volume of gases.

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Boyles Law

• This law is named for Charles Boyle, who studied
  the relationship between pressure, p, and volume,
  V, in the mid-1600s.
• Boyle determined that for the same amount of a
  gas at constant temperature, results in an
  inverse relationshipwhen one goes up, the
  other comes down.

pressure
volume
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What does Boyles Law mean?
A decrease in volume will result in increased
pressure.
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Boyles Law at Work
Doubling the pressure reduces the volume by half.
Conversely, when the volume doubles, the
pressure decreases by half.
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Charles Law

• Charles Law, describes the relationship between
  volume and temperature of gases.

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Charles Law

• This law is named for Jacques Charles, who
  studied the relationship volume, V, and
  temperature, T, around the turn of the 19th
  century.
• This defines a direct relationship With the
  same amount of gas he found that as the volume
  increases the temperature also increases. If the
  temperature decreases than the volume also
  decreases.

volume
temperature
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What does Charles Law mean?
An increase in temperature results in increased
volume.
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Charles Law at Work
As the temperature increases, the volume
increases. Conversely, when the temperature
decreases, volume decreases.
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Gay-Lussac's Law
Gay-Lussacs law states that the pressure of a
fixed amount of gas varies directly with the
temperature when the volume remains constant.
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Gay-Lussac's Law (cont.)
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The Combined Gas Law
The combined gas law states the relationship
among pressure, temperature, and volume of a
fixed amount of gas.
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• Avogadro's Law
• Volume of gas is proportional to the amount
  (moles) of gas V a n
• equal volumes of all gases, at the same
  temperature and pressure, have the same number of
  molecules".

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The Ideal Gas
An ideal gas is defined as one the particles of
which are point masses, showing no interactions
(forces of attractions or repulsions) at all, and
all collisions are elastic
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The Ideal Gas Law
The ideal gas law describes the physical behavior
of an ideal gas in terms of pressure, volume,
temperature, and amount.
The ideal gas constant is represented by R and is
0.0821 Latm/molK when pressure is in
atmospheres.
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