Energy, Temperature, Heat

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Energy, Temperature, Heat
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Recap

• The atmosphere may be divided into layers (or
  regions) according to its
• vertical profile of temperature
• gaseous composition
• electrical properties.
• We live at the bottom of the troposphere, which
  is an atmospheric layer where the air temperature
  normally decreases with height, and is a region
  that contains all of the weather we are familiar
  with.
• The study of the atmosphere and all of its
  related phenomena is called meteorology, a term
  whose origin dates back to the days of Aristotle.

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End of the chapter study material

• Key terms atmosphere, nitrogen, oxygen, water
  vapor, carbon dioxide, ozone, ozone hole,
  aerosol, pollutants and acid rain (Chapter 18),
  outgassing, density, pressure, air pressure,
  lapse rate (6), temperature inversion (3),
  troposphere, radiosonde, stratosphere,
  tropopause, mesosphere, thermosphere, exosphere,
  homosphere, heterosphere, ionosphere, weather,
  climate, meteorology, middle latitudes and middle
  latitude cyclonic storm (12), hurricane (15),
  thunderstorms and tornadoes (14), wind (8), wind
  direction (9), front (11)
• Must learn now
• Will discuss later (in Chapter xyz)
• Questions for review
• Questions for thought
• Problems and exercises
• Questions for exploration

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Energy and Work

• Energy
• Definition The ability or the capacity to do
  work on some form of matter
• Units J (Joule), cal, erg
• Work
• Work is done when a body with a non-zero mass is
  moved (horizontally or vertically) over a
  distance as a result of an acting force.
• Units same as energy, usually J

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What is NOT work???
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Kinetic/Potential Energy

• Kinetic Energy Ek (J)
• Any moving object has a kinetic energy
• High velocity large Ek
• Large mass large Ek
• Fast winds closer to the ground correspond to
  bigger Ek. (Why?)
• Potential Energy Ep (J)
• The potential to do work.
• Gravitational energy (height)
• Elastic energy (deformation)

H
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Energy can produce electricity

• Gravitational potential energy hydropowerplants
• Kinetic energy wind turbines, tidal harnesses
• Radiant (solar) energy solar panels
• Chemical energy batteries
• Nuclear energy nuclear powerplants
• Heat steam engines

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Conservation of Energy

• Energy conservation law
• The total energy of a closed system remains
  constant.
• Energy cannot be created nor can it be
  destroyed!
• Energy can only change from one form to another,
  e.g. kinetic to potential and vice versa.
• Mechanical system
• The loss of Ek in a given process equals the gain
  in Ep in the same process!
• The work is done by gravity or elastic forces.

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Radiant Energy

• The energy emitted from the Sun is radiant
  energy. It is the most important source of energy
  for the Earths atmosphere.
• Every body emits radiant energy (electromagnetic
  emission).
• Infrared, Visible, ultraviolet, X-rays,

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Thermal Energy and Temperature

• Definition ET is kinetic energy on a
  microscopic (molecular) level.
• The temperature is proportional to the average
  molecular kinetic energy.
• The temperature is a measure of the thermal
  energy.
• The Absolute ZERO!
• No thermal energy.
• The atoms do not move.
• The absolute zero practically cannot be achieved.
  

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Temperature Scales

• Kelvin (absolute scale) K
• No negative values
• Starts with THE O!
• Used in science
• Freezing point 273K
• Boiling point 373K
• Fahrenheit F
• Freezing point 32F
• Boiling point 212F
• 180 intervals
• Celsius (Centigrade) C
• Freezing point 0C
• Boiling point 100C
• 100 intervals

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Scale conversions

• Kelvin -gt Celsius K - 273
  C
• Celsius -gt Kelvin C 273
  K
• Fahrenheit -gt Celsius (F-32) x 5/9
  C
• Celsius -gt Fahrenheit Cx9/532
  F
• Fahrenheit -gt Kelvin ???
• Kelvin -gt Fahrenheit ???

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Heat Q

• Heat is energy in the process of being
  transferred from one object to another.
• The amount of heat is equal to the change of
  energy that results from the process of energy
  transfer.
• Processes of heat transfer
• Conduction
• Convection
• Radiation.

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Heat Capacity

• Heat capacity the amount of heat energy that is
  required to change the temperature of a body by 1
  K.
• Heat capacity Heat energy/Temperature change
• It depends on the material and on the mass of the
  body
• Specific heat capacity the amount of energy that
  is required to change the temperature of 1 gram
  of substance by 1 degree C.
• It does not depend on the mass of the body.
• It depends only on the material of the body.

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Table 2-1, p. 30
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Thermal inertia

• Bodies with a large heat capacity cool and/or
  heat up very slowly.
• Analogy with a heavy body (a big truck)
• Water has a high heat capacity (large thermal
  inertia) 1cal/gram/degree
• Regions near large bodies of water (rivers,
  lakes, oceans) do not experience sharp
  temperature changes. Their climate is mild.
• Air and land have smaller specific heats than
  water.

Figure 3.23
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Phase Changes
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Phase transitions (1 gram of water)
Sensible heat
600 cal
100C
Temperature C
Latent heat
100 cal
80 cal
0C
vapor
water
boiling
ICE
melting
HEAT IN
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Latent heat

• Latent heat the heat required to change a
  substance from one state to another (phase
  change)
• Evaporation/Melting (cools the environment)
• Condensation/Freezing (heats the environment)

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The importance of latent heat