Physics PAK 14 Thermodynamics and Nuclear Physics

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Physics PAK 14Thermodynamics and Nuclear Physics
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Heat Energy

• Q mc?T
• Q is quantity of heat energy
• m is the mass of a sample
• c is the specific heat capacity
• ?T is the CHANGE in Temperature

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Thermometers measure Temperature

• An indication of the kinetic energy state of a
  material
• Systems include Kelvin, Celsius, and Fahrenheit
• ?T for Kelvin and Celsius are the same size

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Specific Heat

• the c in Q mc?T
• The amount of heat energy to increase 1 kg of
  material 1 ºC

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Equilibrium Heat Flow Problems

• Heat energy flows from high temperature to low
• A heat flow problem

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Heat of Fusion/Vaporization

• The changes of state - solid liquid gas
• An energy balance and heat flow problem

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Linear Expansion

• Lo is the original length
• a is the coefficient of expansion
• ?T is the change in temperature
• Generally, an increase in temperature increases
  the length of something

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Atomic Models of Heat
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Heat Transfer

• Conduction - when objects touch and heat flows
  between them
• Convection - when a fluid like air or water
  transfers heat energy
• Radiation - when electromagnetic radiation is the
  transfer energy

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Relation of Pressure,Volume and Temperature in
Gasses

• Ideal Gas Law
• PV nRT
• Can be used to cycle between states in Heat
  engines

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Energy Conversion in Heat Engines is never 100
Efficient

• Second law of thermodynamics - you never get
  something for nothing
• Heat energy spreads out into the universe and is
  never fully recovered in other forms

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Entropy

• The universe tends toward disorder
• ?S ?Q/T
• Times arrow is in one direction

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Atomic Models

• Protons --gt
• Electrons --gt -
• Neutrons

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Representation of Atoms in Atomic Equations

• A is the element
• x is the mass number (neutrons protons)
• z is the atomic number ( protons)

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Atomic Equations must Balance

• Top numbers must balance
• Bottom numbers must balance
• An example

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Unstable Atoms Decay

• 1/2 life is time for 1/2 the material to be gone
• Particles and energy can be released
• alpha particles - helium nuclei
• beta particles - electrons
• gamma radiation - high energy electro-magnetic
  waves (light)

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Decay of material may involve loss of mass.Mass
loss is accounted for in the energy of remaining
mass.

• E mc2

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Fission Reactions

• A large nucleus breaks apart
• The pieces have less mass than when they started
• The missing mass is the energy of the moving
  pieces
• Moving particles are described as HEAT

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Fusion Reactions

• Particles are forced together
• The resulting particle has less mass so it is
  moving
• Moving particles are described as HEAT