PHASES OF MATTER

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PHASES OF MATTER

• There are 3 basic phases of matter solid,
  liquid, gas (plasma).

• Plasma is a gas that contains ions and conduct
  electricity. 99 of the universe (the stars) is
  comprised of plasma. Plasma is sometimes called
  the 4th state of matter.

While different phases have different particle
arrangements, the atomic motion never stops!
? What changes from phase to phase is the amount
of atomic motion and the bonds between the atoms.
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Phase Motion Bonds
Fixed
Vibrations
Solid
Free Motion
Bonded, but free
Liquid
Not bonded!
Free Motion
Gas
No matter what the phase, the molecular motion
never stops. It is described by
The Kinetic Theory of Matter
1) The molecules of a substance are in constant
motion.
2) Collisions between molecules are perfectly
elastic.
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Forces between molecules

• in a gas, the molecules separate spontaneously,
  making particles basically independent of each
  other.

• in liquids and solids, the particles are bonded
  and so they attract when pulled apart. They will
  then repel when too close.

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THE SOLID PHASE

• Solids have a definite shape and a definite
  volume.

• The particles of a solid are bonded in a fixed
  position- they only vibrate!

• A crystalline solid has a regular arrangement
  (and so a set melting point). Ice, sugar, iron.

• An amorphous solid has a random particle
  arrangement (and so an unfixed melting point).
  Wax, butter.

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Properties of Solids (and sometimes fluids)

• Diffusion-- the penetration of one particle into
  a second type.

• Cohesion-- force of attraction between same kind
  of molecules

• Adhesion-- force of attraction between different
  kinds of molecules.

• Ductility-- ability of a solid to be pulled into
  a wire.

• Malleability-- ability of a solid to be hammered
  into a sheet

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• Elasticity-- ability to return to original shape
  when distorting forces are removed.

• Elastic Limit-- the point at which the object
  will not return to its original shape

Stress-- the ratio of force per cross-sectional
area of a stretched object.
units N m2
F A
stress
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Stress produces strain-- the relative amount of
deformation (stretch) produced. It is the ratio
of the change in length to the original length
?l l
there are no units for strain!
strain
Hookes Law within the elastic limit of an
object, the ratio of stress to strain for a given
material will remain constant.
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The numerical constant that reflects the
elasticity of a material is called the Youngs
(or Elastic) Modulus (E).
stress strain
F/A ?l /l
F ? l A?l
E
E
the units would be N/m2, since strain has no
units!
The ratio of breaking force to cross-sectional
area is another useful property. This is called
the Tensile Strength (or Ultimate Strength) of
the material.
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Fbreak A
U
units N/m2
Material E (N/m2) U (N/m2)
Iron 100 X 109 170 X 106
Steel 200 X 109 500 X 106
Copper 120 X 109 230 X 106
Aluminum 70 X 109 200 X 106
Bone 15 X 109 130 X 106
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A piece of 25 gauge (A.162mm2) copper wire is
43.00 cm long when 325 N are hung from it. What
is the new length of the wire?
A .162 mm2
(1 m2/10002 mm2) 1.62 X 10-7 m2
E 11.6 X 1010 N/m2
l 43.00 cm
F l AE
?l
F 325 N
l? ?
(325 N)(43.0 cm) (1.62 X 10-7 m2)(11.6 X 1010
N/m2)
.744 cm
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l? l ?l 43.00 cm .744 cm 43.74 cm
How much force is needed to pull apart a piece of
32 gauge (A.0320 mm2) aluminum wire?
Fbreak ?
A .0320 mm2
(1m2/10002 mm2) 3.20 X 10-8 m2
U 2.4 X 108 N/m2
Fbreak UA
(2.4 X 108 N/m2)(3.20 X 10-8 m2)
7.68 N
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A piece of silver wire that is originally 1.0000
m long is stretched to 1.0043 m when 555 N is
suspended from it. What must be the
cross-sectional area of this wire?
A F?l E??l
E 7.75 X 1010 N/m2
l 1.0000 m
?l l? - l .0043 m
(555 N)(1.0000 m) (7.75 X 1010
N/m2)(.0043 m)
F 555 N
A ?
1.66 X 10-6 m2
(10002 mm2/1 m2)
1.66 mm2
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A force of 31.7 N is used to pull apart a piece
of 25 gauge wire. What material must the wire be
made of?
Fbreak 31.7 N
A .162 mm2
(1 m2/10002 mm2) 1.62 X 10-7m2
U ?
U Fbreak A
31.7 N 1.62 X 10-7m2
1.96 X 108 N/m2
Aluminum
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1 ) A vertical steel (E 200 X 109 N/m2) rod of
cross sectional area .15 m2 has a 2000.0 kg sign
hanging from it. A) What is the stress in the
girder? B)What is the strain on the girder? C)
If the girder was 9.5000 m long before the sign
was hung, how much will it stretch with the sign
on it?
2) A force of 188.4 N is used to pull apart a 24
gauge (A .205 mm2) wire. What must the tensile
strength of the wire?
3) A nylon (E 5 X 109 N/m2) tennis string on a
racket is under a tension of 250 N. If its
diameter is 1.00 mm, by how much is it stretched
if the original length of the wire was 30.0 cm?
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4) How much weight needs to be hung from a brass
(TS 80 X 109 N/m2) wire with a cross sectional
area of .320 mm2 in order to break the wire? 5) A
15.0 cm long animal tendon stretches .37 cm by a
force of 13.4 N. The tendon has a diameter of
.85 cm. What must be the Elastic Modulus of this
tendon? 6) A 43.0 cm piano wire is stretched 2.35
X 10-3 m by a force of 710.0 N. The wire has a
radius of 0.454 mm. What is the Youngs Modulus
of the wire?