Properties of Solids and Fluids

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Properties of Solids and Fluids
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Density

• Density is a property that describes the
  relationship between mass and volume.

Mass (g)
Density (g/cm3)
Volume (cm3)
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• Density describes how tightly packed the atoms or
  molecules in a substance.
• The density of a pure substance is the same
  regardless of the form.

Note Both the paper clip and bike cable are
made of steel
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Calculate the density

• What is the density of a piece of wood that has a
  mass of 25 grams and a volume of 29.4 cm3?
• D (density) mass (mass in grams) / V (volume in
  cm3
• D 25 grams/ 29.4 cm3 .850 g/cm3

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Properties of Solids

• Hardness measure of solids resistance to
  scratching.
• Elasticity measure of a solids ability to be
  stretched and return to its original size.
• Brittleness measure of solids ability to
  shatter upon impact

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• Malleability measure of solids ability to be
  pounded into thin sheets
• Tensile strength measure of how much pulling a
  solid can withstand without breaking.

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Fluids Liquids and Gases

• Viscosity
• Buoyancy
• Archimedes Principle

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Density of Fluids

• Since the atoms in a liquid are not as neatly
  stacked as the atoms in a solid are, the liquid
  tends to take up more space.
• As a result, liquids are typically less dense
  than solids.

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That Crazy Water!

• Water is unusual and an exception. Ice (solid
  form) is less dense than the liquid form.
  Therefore, ICE FLOATS.
• Frozen water molecules freeze into ice crystals
  that are mostly empty space. The molecules are
  more tightly packed in waters liquid form.

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Buoyancy and Archimedes Principle

• A buoyant force is an upward force exerted on an
  object by a fluid in which the object is
  immersed. When an object is placed in a fluid,
  the object displaces some of the fluid. The
  volume of the fluid displaced is equal to the
  volume of the object.
• Archimedes principle - an object in a fluid is
  acted on by a buoyant force equal to the weight
  of the fluid displaced by the object
• Demonstration

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Viscosity

• Viscosity is a property of gases and liquids.
• Viscosity is a measure of the materials
  resistance to flow.
• High viscosity fluids take longer to pour from
  their containers than low viscosity fluids.
• Demonstration

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Why are some liquids more viscous than others?

• Viscosity is determined by the shape and the size
  of the molecules in the liquid.
• Larger molecules create more friction than small,
  smooth molecules.
• Liquids with large molecules will flow at a
  slower rate than liquids made up of small
  molecules.

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Gases

• Charles Law
• Boyles Law
• Pascals Principle
• Bernoullis Principle

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Density of gases

• Gases are always less dense than solids or
  liquids
• Density of gases depends upon the molecular
  weight of the gas particles
• If a gas is lighter than air, it rises above the
  air and if it is heavier it sinks through the air
  to the ground

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Behavior of Gases

• Charles Law says that a volume of a gas will
  increase with increasing temperature.
• As the air in a hot air balloon is heated, volume
  of the balloon increases. As a result, the
  density of the air inside the balloon decreases.
• A hot air balloon will rise because the density
  of the air inside the balloon is less dense than
  the air surrounding the balloon.

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Boyles Law

• If you squeeze the same amount of gas in a
  smaller container, the gas particles collide with
  the walls of the container more often, increasing
  the pressure.
• Boyles law says as the
• pressure of a gas increases
• its volume decreases
• proportionally.

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Pressure

• Pressure is the force of the fluid acting on a
  surface.
• As you increase the
• movement of the
• particles, the pressure
• increases.
• The unit of pressure is a pascal (Pa)

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Pascal's Principle

• Pressure is transmitted undiminished or unchanged
  throughout an enclosed static fluid.

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Bernoullis Principal

• States that as the velocity of a fluid increases
  the pressure exerted by the fluid decreases.
• Demonstration

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Airplane Wing

• The air across the top of a conventional airfoil
  experiences constricted flow lines and increased
  air speed relative to the wing.

• This causes a decrease in pressure on the
  top according to the Bernoulli equation and
  provides a lift force.