Thermodynamics

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Thermodynamics
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RAT 11
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Class Objectives

• Be able to define
• thermodynamics
• temperature, pressure, density, equilibrium,
  amount of substance
• states of matter and define them in the context
  of a phase diagram
• gas laws

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Thermodynamics

• Thermodynamics
• Therme meaning heat, and
• Dynamics meaning strength
• Thermodynamics is the science of what is possible
  and impossible
• Major limitation Cannot predict how long the
  process takes
• (This is the subject of rate processes)

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Thermodynamic Properties

• Temperature degree of hotness
• Rapidly moving molecules (atoms) have a high
  temperature
• Slowly moving molecules (atoms) have a low
  temperature

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Thermodynamic Properties

• Pressure - force per unit area

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Thermodynamic Properties

• Density - mass per unit volume

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Thermodynamic Properties

• Amount of Substance how much is there

1 2 3 12
144
6.022 1023
Dozen
Gross
Avogadros Number
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Pair Exercise 1

• A cube of osmium measures 0.2 m on a side. It
  sits on a table. At the contact between the
  table and osmium, calculate the pressure (N/m2).
• Note Densities may be found in Table 11.1
  Foundations of Engineering

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States of Matter
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Pressure, Temperature, and State
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Gas Laws

• apply only to perfect (ideal) gases
• Boyles Law
• Charles Law
• Gay-Lussacs Law
• Mole Proportionality Law

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Boyles Law
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Charles Law
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Gay-Lussacs Law
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Mole Proportionality Law
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Perfect Gas Law

• The physical observations described by the gas
  laws are summarized by the perfect gas law
  (a.k.a. ideal gas law)
• PV nRT
• P absolute pressure
• V volume
• n number of moles
• R universal gas constant
• T absolute temperature

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Values for R
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Pair Exercise 2

• A balloon is filled with air to a pressure of 1.1
  atm. The filled balloon has a diameter of 0.3 m.
  
• A diver takes the balloon underwater to a depth
  where the pressure in the balloon is 2.3 atm.
• If the temperature of the balloon does not
  change, what is the new diameter of the balloon?

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Energy

• Energy is the capacity to do work, but work is a
  form of energy...
• It is easier to think of energy as a scientific
  and engineering unit of exchange, much like
  money is a unit of exchange.
• Example
• 1 car 20k
• 1 house 100k
• 5 cars 1 house

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Energy Equivalents

• A case for nuclear power?
• 1 kg coal 42,000,000 joules
• 1 kg uranium 82,000,000,000,000 joules
  (82x1012)
• 1 kg uranium 2,000,000 kg coal!!

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Heat

• Heat is the energy flow resulting from a
  temperature difference.
• NOTE HEAT AND TEMPERATURE ARE NOT THE SAME!

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Example
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Work

• Heat flows due to a temperature driving force
• Work is the energy flow from any other driving
  force

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Types of Work
Work Driving Force
Mechanical Force (Physical)
Shaft work Torque
Hydraulic Pressure
Electric Voltage
Chemical Concentration
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Mechanical Work
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Mechanical Work
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PV Work (Hydraulic)
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Pair Exercise 3

• An ideal gas is contained in a closed system.
  Under constant pressure, the container is
  compressed from V1 to V2 (volume). Derive the
  equation for work in terms of the universal gas
  constant and temperature.