Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine [e-mail]

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Introduction to Physical ScienceMonday,
Wednesday, ThursdayTom Burbinetomburbine_at_astr
o.umass.edu
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Midterm

• Thursday
• You can bring in one sheet of paper with anything
  written on it
• Covers everything up to Wednesday

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Heat Transfer

• Conduction
• Convection
• Radiation

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Conduction

• Transfer of internal energy by molecular and
  electronic collisions within a substance
  (especially a solid)
• Metals are good conductors since the electrons
  are held loosely
• Poor conductors are made up of molecules that
  hold tightly to their electrons

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Convection

• Transfer of internal energy in a gas or liquid by
  means of currents in the heated fluid. The fluid
  flows, carrying energy with it

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Radiation

• The transfer of energy by means of
  electromagnetic waves (forms of light)

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• Everything radiates energy
• Everything is also absorbing energy
• Black surfaces absorbs radiation better than
  white surfaces

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Stefan-Boltzman Law
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• Thermal equilibrium is achieved when two systems
  in thermal contact with each other cease to have
  a net exchange of energy

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Greenhouse Effect

• The greenhouse effect is the rise in temperature
  that a planet experiences because certain gases
  in the atmosphere (H2O, CO2, CH4, O3) trap energy
  emitted from the surface.

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Greenhouse Effect

• Visible light hits the surface
• Surface warms and emits infrared radiation
• Atmospheric gases absorb some of the infrared
  light
• Surface and atmosphere heat up

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Stefan-Boltzman Law
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Runaway Greenhouse Effect

• Runaway greenhouse effect to describe the effect
  as it occurs on Venus
• Venus is sufficiently strongly heated by the Sun
  that water is vaporized and so carbon dioxide is
  not reabsorbed by the planetary crust

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Billion Metric Tons Carbon
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Changes of phase
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When matter changes phase

• When matter changes phase, a transfer of internal
  energy is involved

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Changes of phase

• Evaporation phase change from liquid to gas
• Sublimation phase change from solid to gas
• Condensation change of phase from a gas to a
  liquid

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• Evaporation cools the liquid left behind
• Condensation warms the object that it condenses on

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• Which is worse
• A burn from 100 oC steam or 100 oC water?

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• After a shower, why are you colder outside the
  shower than inside the shower stall?

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Any Questions?