Physical Science

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Physical Science

• Chapter 8 Solids, Liquids, and Gases

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Kinetic Theory of Matter
All matter is in constant motion. Solid -
particles are close together in a fixed
location Liquid - particles are freely moving but
attractive forces between the particles exist gas
- particles are in constant random motion with
little attraction between particles
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Solids
Crystalline solids - solids whose particles make
up a regular repeating pattern. Unit cell -
smallest repeating unit of a crystalline
solid Brittle, breaking into smaller
crystals High melting points
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Liquids
Definite volume - no definite shape viscosity -
measure of the ability of flow Surface Tension -
skin like layer produced by the attraction of
molecules at the surface. Evaporation - escape of
particles from the surface of a liquid as they
gain kinetic energy.
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Kinetic Theory of Gases
Ideal Gas - imaginary gas which conforms
perfectly to the assumptions of the kinetic
theory.
1. Gases consist of large numbers of tiny
particles. 2. Gas particles are in constant
random motion, and thus possess kinetic
energy. 3. The collisions between gas particles
and container walls are perfectly elastic. 4.
There are no forces of attraction or repulsion
between particles of a gas. 5. The average
kinetic energy of a gas is directly proportional
to the kelvin temperature.
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Nature of Gases
Expansion - gases fill an entire volume of the
container they are in. Fluidity - Gases, like
liquids flow and are therefore considered
fluids. Low Density - usually measured in g/L not
g/mL Compressibility - Volume of a gas can be
changed easily Diffusion - spreading out and
natural mixing of gas particles.
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Pressure and Gas
Pressure - force per unit of area at the
surface. Pressure force
N/m2 Pascal (Pa)
area
Pascal (Pa) is the SI unit of pressure.
Other units of pressure psi - pounds per square
inch mmHg - millimeters of mercury
(barometer) inHg - inches of mercury
(barometer) atmospheres (atm) - pressure at sea
level is 1 atm
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Standard Pressure
1.00 atm 101.3 kPa (kilopascals) 760 mmHg 14.7
psi 30.0 inHg
1. 332 kPa ? atm 2. 7.32 psi ? kPa 3. 1.75
atm ? mmHg 4. 31.33 in Hg ? mmHg 5. 933 mm
Hg ? kPa
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Boyles Law
The volume of a fixed mass of gas varies
inversely with the pressure at constant
temperature.
P1V1 P2V2
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Boyles Law Problem
A sample of oxygen gas collected in the
laboratory occupies a volume of 150.0 mL when its
pressure is 720.0 mm Hg. What volume will the
gas occupy at 750.0 mm Hg if the temperature
remains constant?
What is the question asking for?
V2
V2 P1V1
________
V2 (720.0 mm Hg)(150.0 mL)
____
____________________________
P2
________
750 mm Hg
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Charles Law
The volume of a gas is directly proportional to
its Kelvin temperature as the pressure is
constant.
V1
V2
___
___

T1
T2
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Charles Law
6.7 liters of a gas at 0oC is heated to 27oC.
What is the new volume of gas assuming the
pressure is constant?
What is the question asking for?
V2
V1T2
V2

_________
T1
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STP Standard Temperature and Pressure
Standard Temperature 0oC or 273 K

• Standard Pressure
• 1.00 atm
• 101.3 kPa
• 760 mm Hg
• 14.7 psi

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Gay-Lussac Law
The pressure of a gas is directly proportional to
the Kelvin temperature if the volume remains
constant.
P1
P2
_____
_____

T1
T2
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Gay-Lussac Practice Problem
The gas in an aerosol can at room temperature
(27oC) and standard pressure is heated so that
the pressure in the can rises to 3.5 atm. What
is the temperature of the gas in the can?
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Combined Gas Law
P1V1
P2V2
_____
_____

T2
T1
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Practice Problem
A balloon at STP has a volume of 3.44 liters.
The balloon rises to an altitude where the
temperature falls to -5.00oC and the pressure
decreases to 95.5 kPa. What is the volume of the
balloon?
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Changes of phases of matter

• Freezing point and melting point - same
  temperature.
• Boiling point and condensation point - same
  temperature.
• Sublimation - change from a solid to a gas or
  from a gas to a solid.

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Heating Curves
Temperature
boiling
melting
Heat energy
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Archimedes Principle
Buoyant force - the upward force in a liquid or a
gas upon an object immersed in it. Archimedes
Principle - the buoyant force of an object in a
fluid is equal to the volume of fluid displaced
by the object.