Laws Regulating Energy

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Laws Regulating Energy

• ChemCom Notes

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Laws Regulating Energy

• Also called the laws of Thermodynamics
• Zero Law Energy Transfer
• First Law Conservation of Energy
• Second Law Entropy
• Third Law Absolute Zero

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Zero Law Energy Transfer

• Energy will be transferred from areas of high
  temperature to areas of low temperature until the
  difference in temperature is zero.

25ºC 15ºC
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First Law Conservation of Energy

• Total energy in the universe is constant. Energy
  is never actually created or destroyed. It only
  changes from one form to another, or moves from
  one place to another, or is converted to mass.

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Refresher Time

• Find someone else in class (not sitting in your
  seating group) who is wearing the same color as
  you are.
• Discuss the following questions and be ready to
  report out
• What are three things that always make you laugh?
• What are two things you are afraid of?
• What is one thing you are good at doing?

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Second Law - Entropy

• All things (mass and energy) tend toward
  disorder. So within any given system, energy will
  move from a state of organization toward a state
  of randomness. As disorder increases, energy
  changes into less usable forms. Because of this,
  any process that harnesses energy always loses
  some along the way-conversion can never be 100
  percent efficient.

100
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Third Law Absolute Zero

• Molecular movement stops at absolute zero
  (-273C). Since temperature measures how fast
  molecules move, there can be no temperature lower
  than absolute zero.

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Other Important Ideas

• Useful Energy
• Energy Efficiency

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Useful Energy

• The desired output energy of an energy
  conversion. In an electric oven the input
  electric energy is consumed while the oven is on,
  and the useful output energy is the thermal
  energy used to bake or cook the food.
• Input Energy Useful Output Energy

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Energy Efficiency

• No energy conversion is 100 efficient, but the
  energy is not lost. Energy is ALWAYS conserved
  but it is not always in a form that is useful.
  In science, energy efficient measures the ratio
  of useful output energy to input energy(Alberta
  Education). The debate regarding ethanol is a
  good example of a debate focused on energy
  efficiency.

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Energy Efficiency Calculations

• Energy Efficiency is calculated by determining
  the amount of useful energy and dividing it by
  the input energy. Remember it cannot be 100 or
  more so that is a great way to check your math!

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Energy Efficiency Example

• Information A burner on a stove uses the
  equivalent of 200 therms of energy to heat the
  burner to the equivalent of 150 therms.

• Which is the useful energy?
• Which is the input energy?
• What is the energy efficiency?

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Energy Efficiency Practice

• A Flashlight uses 55 units of energy to produce
  12 units of light. What is the efficiency of the
  flashlight?

• A outdoor grill in the winter time uses 1,905
  units of energy to produce the heat needed (245
  units of energy) to cook a burger. How efficient
  is this?