States of Matter

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Chapter 13 States of Matter
Anything in black letters write it in your
notes (knowts)
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Unit Preview
Atoms and molecules are always moving, even in a
solid or liquid.
The particles of a gas are moving much faster
though.
This unit is about gases and vapors. Remember
that air is a gas also!
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13.1 The Nature of Gases
Gas particles are constantly moving and exert a
force on the container.
Forces are measured in Newtons and area is
measured in meters2
1 kilopascal (kPa) 1000 Pa
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Other units of pressure
mmHg
p.s.i.
atmosphere (atm)
A barometer measures gas pressure
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Aneroid Barometer
Aneroid without fluid
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Atmospheric Pressure (Patm)
The pressure exerted by the gases in atmosphere.
Standard Atmospheric Pressure
1 atm 101.325 kPa 760 mmHg 29.9
inHg 14.7 p.s.i.
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Atmospheric Pressure is Powerful!
1 m
101.325 kPa 101,325 N/m2
1 m
101,325 N
1 lb
1 ton
x
x
1 m2
4.45 N
2000 lb
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Atmospheric Pressure is Powerful!
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Atmospheric Pressure is Powerful!
Empty space with no particles or pressure is
called a vacuum.
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14.1 Properties of Gases
Solids and liquids are NOT easily compressible
gases are.
Why do you think gases are compressible?
- there is a large amount of space between gas
particles.
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What will happen to the pressure (P) of a gas if
the temperature (T) increases?
P ?
Gay Lussacs Law
the volume (V) of the container increases?
P ?
Boyles Law
the number of molecules (n) increases?
P ?
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What will happen to the volume (V) of a gas if
the temperature (T) increases?
V ?
Charless Law
the pressure (P) on the gas increases?
V ?
Boyles Law
the number of molecules (n) increases?
V ?
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Three Gas Law Equations
P1V1 P2V2
Boyles Law
V1 V2 T1 V2
Charless Law

P1 P2 T1 T2
Gay-Lussacs Law

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Tk Tc 273
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The volume of a gas depends on its temperature
and pressure.
STP Standard Temperature Pressure
Standard Temp 0C 273 K
Standard Pressure 101.3 kPa
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The Combined Gas Law Equation
Why is it called The Combined Gas Law?
- it combines Charless, Boyles and Gay-Lussacs
Laws into one
T MUST be in kelvin
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14.3 Ideal Gases
4 variables that describe gases.
Pressure (kPa) Volume (L) Temperature
(K) number of particles (mol)
P V T n
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The Ideal Gas Law Equation
universal gas constant
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The particles of an ideal gas have no volume, and
there is no attraction between them.
Ideal gases do not exist, but real gases behave
like ideal gases at many conditions of
temperature and pressures.
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Avogadros Hypothesis
Equal volumes of gases, at the same temp and
pressure, contain the same number of molecules.
Lorenzo Romano Amedeo Carlo Avogadro di Quaregna
e di Cerreto (1776 1856)
Also came up with the idea of the mole 6.02 x
1023 Avogadros Number
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These balloons contain gases with the same
temp, same pressure, same volume,
Cl2
H2
O2
Each of these balloons has the same number of
molecules inside them.
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Use the ideal gas law to calculate the volume of
1 mole of any gas at STP.
1 mole of any gas has a volume of 22.4 L at STP.
The molar volume of a gas at STP.
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1. What is the volume of 1 mole of nitrogen gas
at STP?
2. What is the volume of 1 mole of nitrogen gas
at 22C and 99.8 kPa?
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13.2 The Nature of Liquids
Temperature is a measure of the AVERAGE kinetic
energy of molecules.
Molecules with higher than average kinetic energy
can evaporate.
Kinetic Energy (KE) energy due to motion.
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Vapor pressure -
pressure due to evaporating particles of a solid
or liquid.
A substance with a high vapor pressure (volatile)
will evaporate quickly.
Vapor pressure increases as temp increases.
When the vapor pressure equals atmospheric
pressure, boiling occurs.
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Vapor Pressure of Water
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Boiling point depends on atmospheric pressure
Normal Boiling Point -
temp where v.p. of liquid equals 101.3 kPa
Higher elevations have lower Patm, so water boils
at a lower temperature (not as hot).
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Molecules with higher KE evaporate
The molecules left behind have a lower average KE
Evaporation is a COOLING PROCESS!!
Evaporation is COOL!
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Evaporation occurs at the surface of a liquid,
boiling occurs throughout the liquid.
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Dynamic Equilibrium vaporization rate
condensation rate.
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Measuring the volume of a gas collected by water
displacement.
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Measuring the volume of a gas collected by water
displacement.
Poutside
Pinside
1. Raise/lower flask until Pinside Poutside
(water levels are equal)
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Measuring the volume of a gas collected by water
displacement.
Patm
Pgas Pwater vapor
2. Pgas Patm Pwater vapor
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Chapter 13 14 Review

1. Define Pressure.
2. State 3 units of pressure
3. What is a volatile liquid?
4. Explain how evaporation is a cooling process.
5. What is vapor pressure?
6. When does boiling occur?
7. Explain the difference between boiling
   evaporation.

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Chapter 13 14 Review

• 8. What does STP stand for (in this class)?
• 9. If 10 mL of O2 at STP are heated to 100C,
  what does the volume become? The pressure
  remains constant.
• 10. How many moles of O2 are in problem 9?

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Chapter 13 14 Review

• State Avogadros Hypothesis
• What is the volume of 1 mol of any gas at STP?
• What does each letter in PVnRT stand for?
• What units should be used in PVnRT?
• 500mL of any gas would contain how many moles at
  STP?

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What is the normal boiling point of ethanol? What
is the boiling point of water when atmospheric
pressure is 60kPa?