Properties of Fluids

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Properties of Fluids

• Unit 5 Hydraulic and Pneumatic Systems
• Lesson 1

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Properties of Fluids

• The science and technology of the mechanical
  properties of liquids is called hydraulics.
• Similarly, the science and technology of air and
  other gases is called pneumatics.

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• A Fluid is a substance that flows and takes the
  shape of its container liquids and gases are
  both fluids.
• If the fluids are at rest, the study of them is
  called fluid Statics.

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• The study of hydraulics and pneumatics includes
  the study of fluids that are not enclosed, such
  as lakes and air in the atmosphere as well as
  pressurized systems that are enclosed.
• A hydraulic system is a mechanical system that
  operates using a liquid under pressure
• A pneumatic system operates using a gas under
  pressure.

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Density and Compressibility

• All Matter is made up of extremely tiny particles
• Each Pure substance has its own kind of
  particles, different from the particles of other
  pure substances
• Particles are always moving. Particles at a
  higher temperature are generally moving faster,
  on average than particles at a lower temperature.
  
• Particles attract each other

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There are three states of matter.

• Gas, Liquid, and Solid. All three of these
  states are physical states of matter.

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• There is also a forth, it is called a plasma
  which has charged particles that can conduct
  electricity and are influenced by magnetic
  fields. It is similar to a gas in its properties

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Physical Properties of Solids, Liquids and Gases
Phase Structure Movement of Particles Shape of Sample Density Compressibility
Solid - Particles closely packed - Particles in fixed positions - Vibration -Definite shape -Volume of its own -Usually more dense than liquid or gas -Cannot be compressed significantly
Liquid -Particles Closely packed - Particles not fixed in position - Vibration - Rotation - Translation (slower) - Takes shape of container - Volume of its own - Usually less dense than solid - Cannot be compressed significantly
Gas - Particles widely spaced - Particles not fixed in position - Vibration - Rotation, - Translation (fast) - Occupies entire volume of container - Much less dense than solid or liquid - Can be easily compressed
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• Two properties of matter that are particularly
  important to the study of fluids are density and
  compressibility.
• Density The mass per unit volume of a
  substance it is a scalar quantity with SI units
  of kg/m3

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Density
Density can be found using the formula Volume Mass
Where D is the density, m is the mass and V is
the volume
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Example1

• A quantity of helium gas at 0 C with a volume of
  4.00 m3 has a mass of 0.712 kg. (in this case the
  helium gas is at atmospheric pressure.) Determine
  the density of this sample of helium gas.
• V 4.00 m3
• m 0.712 kg
• D ?

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• D 0.178 kg/m3
•  
• The density of the helium gas sample is 0.178
  kg/m3

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• Density is a characteristic property of a
  substance, any sample of a pure substance has the
  same density. It does not matter how large or
  where the sample was taken from.
• The density of a substance can also be used to
  identify an unknown sample.

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• NOTE The temperatures of all samples must be
  stated when comparing densities the pressure of
  the gas should also be stated as density
  increases in gasses as pressure increases.

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• Compressibility the ability of the particles of
  a substance to be pressed closer together.
• Particles in gasses are spread out, this makes
  them highly compressible. Liquids on the other
  hand are only slightly compressible and solids
  are even less compressible. The property of
  compressibility influences the choice between
  hydraulic and pneumatic systems.

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Questions

• For each of the following substances, calculate
  the density in a convenient unit. See the extra
  table given to you to determine the substance.
• A volume of 0.50 m3 of a substance has a mass of
  6.3 x 102 kg
• A volume of 5.00 L of a substance has a mass of
  3.95 x 103 g
• A volume of 75 mL of a substance has a mass of 77
  g
• A rectangular solid brass plate is 8.0 cm long,
  6.0 cm wide, and 1.5 cm thick.
• Calculate the volume of the plates in cubic
  centimetres.
• Calculate the plates mass in grams and kilograms.
  

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• Water can be observed as a ice, water, and
  vapour. Which of these states can be called a
  fluid?
• What is the difference between hydraulics and a
  hydraulic system?
• A block of metal is 50.0 cm long, 20.0 cm wide,
  and 15.0 high. Its mass is 128 kg.
• Write the blocks dimensions in metres
• Calculate the volume of the block in cubic metres
• Calculate the blocks density
• What is the identity of the metal ?