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Energy, Heat, and Entropy

Energy, Heat, and Entropy. Definitions. Energy = ability to do work (expressed in Joules) Work (also expressed in Joules) = Force (in Newtons ) X Distance (Meters) Power (Watts) = Joules per second Kinetic Energy = ½ (kg x v 2 ) = ½ ( kgxhxg ) Potential Energy = (kg x v 2 ); (kg x c 2 ).

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Energy, Heat, and Entropy

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  1. Energy, Heat, and Entropy

  2. Definitions • Energy = ability to do work (expressed in Joules) • Work (also expressed in Joules) = Force (in Newtons) X Distance (Meters) • Power (Watts) = Joules per second • Kinetic Energy = ½ (kg x v2) = ½ (kgxhxg) • Potential Energy = (kg x v2); (kg x c2)

  3. James Watt • Inventor and natural philosopher • Member of the Lunar Society • Made improvements to the original Newcomen Steam engine by adding a condensing chamber 1736-1819

  4. Watt-Boulton Steam Engine of 1784 • B steam valve • C steam chamber • E exhaust steam valve • N cold water pump • P piston • Q regulator/governor • T steam input flap controlled by regulator

  5. Sadi Carnot • When a system goes through different energetic states and returns to its original state, a thermodynamic cycle has occurred. • While a cycle occurs, work can be done • There must be an absolute low temperature 1796-1832

  6. Concepts of Heat • Considered an element in Aristotelian and Alchemical systems • Even Lavoisier (founder of modern chemistry) considered it an element • Motion of atoms (Boyle) • Heat is a form of energy (Count Rumford)

  7. Robert Boyle and Boyle’s Law Image from NASA 1627-1691

  8. Benjamin Thompson, Count Rumford • Born in Massacheusetts • Property in Concord (Rumford) • Royalist during the revolution (worked on force of gunpowder) • Moved to London and then to Bavaria 1753-1814

  9. no mass change after heat transfer • work boring cannons could boil water (it was thought that chopping up matter released caloric, but Rumford pointed out that more work equals more heat, whereas caloric would be finite in amount) • cannons firing blanks get hotter than cannons firing cannonballs • Published in 1798 by Royal Society

  10. James Prescott Joule • Nature of heat • Heat and mechanical energy • Heat and electrical energy 1818-1889

  11. Joule’s Apparatus

  12. Rudolph Clausius • Built on Carnot’s engine to develop a theory of heat that became the laws of thermodynamics • On the Mechanical Theory of Heat (1850). A statement of the second Law of thermodynamics 1822-1888

  13. William Thompson, Lord Kelvin • Clearly defined 1st and 2nd laws of thermodynamics • Determined -273.15C is absolute zero • Absolute temperature scale defined in degrees Kelvin • Knighted for his role in laying transatlantic cable • Used thermodynamics to determine the age of the earth 1824-1907

  14. Laws of Thermodynamics • Energy is conserved in a closed system, but it can be transferred from one form to another. For example heat and work are types of energy transfer. • Entropy – a closed system tends toward thermodynamic equilibrium • Entropy of a closed system approaches a constant as the temperature approaches absolute zero. That is, the entropy of a crystal at absolute zero is zero.

  15. Forms of Energy Ionization Elastic Sound Gravitational Intrinsic (E=mc2) Thermal • Kinetic • Chemical • Electric • Magnetic • Electromagnetic radiation • Nuclear

  16. Entropy and Time Carnot engine

  17. Heat Transfer

  18. Meteor airbursts Aftermath of the Tunguska event (19 years after the airburst on 30 June 1908) Chelyabinsk meteor Feb 15, 2013

  19. Meteor Strikes • Types of meteorites • Chondrites • Iron-nickel • Others are fragments of planets and the moon

  20. Mechanism of the Meteor Strike

  21. Meteor Crater Winslow Arizona Diameter 1-1.25 km

  22. Crater Copernicus Diameter 93 Km

  23. ChicxulubImpactor KT-Asteroid Strike 65 mya Crater diameter 180 km

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