Section 13'4 Solids

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Section 13.4 Solids

• Objectives
• Relate the properties of solids to their
  structures.
• Explain why solids expand and contract when the
  temperature changes.
• Calculate the expansion of solids.
• Explain the importance of thermal expansion.

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INTRODUCTION

• Solids differ from liquids in that they are
  stiff, they can be cu in pieces, and they retain
  their shape. You can push on solids but if you
  try to push on a liquid your hand will move
  through it.

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SOLID BODIES

• Crystal Lattice structure of solid consisting
  of regular arrangements of atoms.
• Amorphous Solids solids that have no long range
  order meaning no crystal structure. The
  particles are fixed but the pattern is variable.
  They have definite volume and shape but no
  regular crystal structure.
• Amorphous solids also are classified as viscous,
  or slowly flowing, liquids.
• As a liquid becomes a solid, its particles
  usually fit more closely together than in the
  liquid state, making solids more dense than
  liquids.

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SOLID BODIES

• However, water is an exception because it is most
  dense at 4C. Water is also an exception to
  another general rule. For most liquids, an
  increase in the pressure on the surface of the
  liquid increases its freezing point.
• Because water expands as it freezes, an increase
  in pressure forces the molecules closer together
  and opposes the freezing. Therefore, higher
  pressure lowers the freezing point of water very
  slightly.
• Elasticity ability of an object to return to
  its original shape after deforming forces are
  removed. It depends on the electromagnetic
  forces that hold the particles of a substance
  together.
• Malleability the ability of a solid to be
  rolled into a thin sheet
• Ductility the ability of a solid to be drawn
  into a wire.

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THERMAL EXPANSION OF SOLIDS

• Thermal Expansion increase in length or volume
  of an object due to change in temperature. Most
  objects will expand when heated and contract when
  cooled.
• Coefficient of Linear Expansion change in
  length divided by original length and by
  temperature change.
• ? ?L / L1?T
• Coefficient of Volume Expansion change in
  volume divided by original volume and by
  temperature change.
• ? ?V / V1?T

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THERMAL EXPANSION OF SOLIDS

• Table 13.2 p. 361

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THERMAL EXPANSION OF SOLIDS

• Example 4 p. 363
• ? ?L / L1?T
• ? .0017 / (1.6 (84 21) )
• .000017 ?C-1
• Skip Practice Problems p. 362
• Skip 13.4 Section Review

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SWIMMING UNDER PRESSURE

• Ships can float because the hull is hollow and
  large enough so the average density of the ship
  is less than the density of water. You can
  notice that a ship filled with cargo will be
  submerged more than a ship with no cargo.
• Example 3 p. 356
• a. Fbuoyant ?Vg b. Fg mg ?Vg
  Fapparent Fg Fb
• Fbuoyant 1000(.001)(9.8) Fg
  2700(.001)(9.8) Fa 26.46 9.8
• Fbuoyant 9.8 N Fg 26.46 N
  Fa 16.66 N
• Skip Practice Problems p. 356

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FLUIDS IN MOTION BERMOULLIS PRINCIPLE

• Bernoullis Principle states that as the
  velocity of a fluid increases, the pressure
  exerted by that fluid decreases. Or when a fixed
  quantity of fluid flows, the pressure is
  decreased when the velocity increases.
• There are many common applications of Bernoullis
  principle, such as paint sprayers and perfume
  bottles.
• A gasoline engines carburetor, which is where
  air and gas are mixed, is another common
  application of Bernoullis principle.
• Part of the carburetor is a tube with a
  constriction, as shown in figure 13-16b.
• Streamlines lines representing the flow of
  fluids around objects.
• Skip 13.3 Section Review