Thermodynamics

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Chapter 11

• Thermodynamics

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Heat

• Heat can be used to do work (W)
• Heat can be transferred to a substance as heat
  and from a substance as work.
• They can both be transferred to or from a system
• We use the variable Q for heat

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Heat

• System a collection of matter within a clearly
  defined boundary across which no matter passes
• Environment everything outside a system that can
  affect or be affected by the systems behavior

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First Law

• The First Law of Thermodynamics
• The principle of energy conservation that takes
  into account a systems internal energy as well
  as work and heat.

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Second Law

• Second Law of Thermodynamics No cyclic process
  that converts heat entirely into work is
  possible.
• Some energy must always be transferred as heat to
  the systems surroundings

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Second Law

• Cyclic process a thermodynamic process in which
  a system returns to the same conditions under
  which it started.

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Entropy

• Entropy is a measure of a systems disorder.
• Systems with maximum disorder are favored. An
  ordered system is likely to become disordered.
• Once a systems has reached a state of greatest
  disorder, it will tend to remain in that state
  and have maximum entropy.

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Entropy

• Increasing disorder reduces the energy available
  for work.
• Entropy doesnt have to increase. In a system, we
  can arrange for increase or decrease in entropy.
• If we increase the order (decrease the entropy)
  of a system, then we the entropy of the
  environment will increase
• If you clean your room (increase the order), you
  will release heat into the air from all the work
  you are doing, thereby increasing the entropy of
  the environment

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Entropy

• The second law of thermodynamics can be expressed
  in terms of entropy change.
• The entropy of the universe increases in all
  natural processes.

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FYI

• Ultimately the entropy of the universe should
  reach a maximum value. At that time, the universe
  will be in a state of thermal equilibrium and its
  temperature will be uniform throughout. This
  means no transfer of heat can occur, thus no work
  can occur. All physical, chemical, and biological
  processes will stop because of the absence of
  energy to do work. This is called the heat
  death of the universe.
• ETA 100 trillion years from now.

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Homework

• P424 Section Review 1
• P429 Section Review 2