Lesson 1: Basic Terminology

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Lesson 1 Basic Terminology

• This lesson reviews terms used to describe the
  properties and behavior of gases.

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Opening thoughts

• Have you ever

Seen a hot air balloon?
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Opening thoughts

• Have you ever

Seen a hot air balloon?
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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E. Pressure

• Barometer
• measures atmospheric pressure

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E. Pressure

• Manometer
• measures contained gas pressure

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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. (OK, how big two of them
are)
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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 (in kg) to the
number of moles, n, using the molecular or
formula weight of the gas.
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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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.

Lets go!
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A. Kinetic Molecular Theory

• Particles in an ideal gas
• have no volume.
• have elastic collisions.
• are in constant, random, straight-line motion.
• dont attract or repel each other.
• have an avg. KE directly related to Kelvin
  temperature.

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B. Real Gases

• Particles in a REAL gas
• have their own volume
• attract each other
• Gas behavior is most ideal
• at low pressures
• at high temperatures
• in nonpolar atoms/molecules

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C. Characteristics of Gases

• Gases expand to fill any container.
• random motion, no attraction
• Gases are fluids (like liquids).
• no attraction
• Gases have very low densities.
• no volume lots of empty space

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C. Characteristics of Gases

• Gases can be compressed.
• no volume lots of empty space
• Gases undergo diffusion effusion.
• random motion

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E. Pressure

• KEY UNITS AT SEA LEVEL
• 101.325 kPa (kilopascal)
• 1 atm
• 760 mm Hg
• 760 torr
• 14.7 psi

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F. STP
STP
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Lesson 2 Boyles Law

• This lesson introduces Boyles Law, which
  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?
Suppose you have a cylinder with a piston in the
top so you can change the volume. The cylinder
has a gauge to measure pressure, is contained so
the amount of gas is constant, and can be
maintained at a constant temperature. A decrease
in volume will result in increased pressure. Hard
to picture? Lets fix that!
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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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Lesson 2 Complete!

• This concludes Lesson 2 on Boyles Law!

Click the Main Menu button below, then select
Lesson 3 to learn about how temperature fits in.
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Lesson 3 Charles Law

• This lesson introduces Charles Law, which
  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?
Suppose you have that same cylinder with a piston
in the top allowing volume to change, and a
heating/cooling element allowing for changing
temperature. The force on the piston head is
constant to maintain pressure, and the cylinder
is contained so the amount of gas is constant. An
increase in temperature results in increased
volume. Hard to picture? Lets fix it (again)!
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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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Lesson 3 Complete!

• This concludes Lesson 3 on Charles Law!

Click the Main Menu button below, then select
Lesson 4 to put all the pieces together with the
Ideal Gas Law.
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Lesson 3 Complete!

• This concludes Lesson 3 on Charles Law!

Click the Main Menu button below, then select
Lesson 4 to put all the pieces together with the
Ideal Gas Law.
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Mission complete!

• You have completed the lessons and review.
  Congratulations!
• You should now have a better understanding of the
  properties of gases, how they interrelate, and
  how to use them to predict gas behavior.
• Please click on the button below to reset the
  lesson for the next student. Thanks!

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