Energy / Thermodynamics (Heat) - PowerPoint PPT Presentation

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Energy / Thermodynamics (Heat)


I. Energy: A. The ability of an ... Work: transfer of energy through motion. (It is zero work if object doesn't move.) A. Work involves Force and Displacement ... – PowerPoint PPT presentation

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Title: Energy / Thermodynamics (Heat)

Energy / Thermodynamics (Heat)
  • I. Energy
  • A. The ability of an object to produce
    change in the environment or in itself.
  • B. Types kinetic vs. potential
  • C. Many forms including thermal, light,
    electrical, chemical, nuclear, electromagnetic,
    solar, mechanical (sum of kinetic potential)
  • D. Energy can be transferred from one form
    to another.
  • E. Energy is conserved (law of
  • II. Work transfer of energy through motion.
    (It is zero work if object doesn't move.)
  • A. Work involves Force and Displacement
    (movement, change in position).
  • B. Formula W F x d (work force
    (wt) x displacement)
  • C. Work units are Nm (Newton-meters) OR J

  • III. Simple Machines Tools that enable (F)
    (d) to be varied while keeping work constant.
  • A. Can reduce (F) by increasing (d)
    through which force is exerted.
  • B. Examples
  • 1. Inclined plane 5. Wedge
  • 2. Lever 6. Screw
  • 3. Pulley 7. Block tackle
  • 4. Wheel axle
  • IV. Friction force opposing motion, energy
    used to overcome friction changes to heat.
  • V. Power rate at which work is done, measure
    of the amount of work done in a certain amount of
  • A. Calculated by P W/t
  • B. Units are in watts (W) 1W1

  • VI. Chemical potential energy food
  • A. Food is the energy (chemical PE) our
    bodies need to help our bodies do work (KE).
  • B. A food Calorie (measures energy from
    food) is equal to 1 kilocalorie ? 4180 J)
  • VII. Thermal Energy / Heat (thermodynamics)
  • A. The transfer of energy from a higher
    temperature body to a lower temperature body.
  • B. Involves Energy transfer and Energy

  • VIII. Molecular Kinetic Energy (KE) and
    Temperature (temp).
  • A. All molecules have KE.
  • 1. The more energy molecules absorb, the
    greater their KE.
  • 2. Ex Hot water has more KE than cold water.
  • B. Temperature-a measure of the average KE
    of molecules.
  • 1. The faster the molecules move, the higher
    the temp.
  • 2. Temp. Scales most countries use the
    Centigrade (Celsius) scale.
  • a. Centigrade (Celsius)- ?C, water boils
    at 100?C, water freezes at 0?C
  • b. Fahrenheit -?F, water boils at 212?F,
    water freezes at 32?F
  • c. Kelvin-(K) A thermodynamic Celsius
    temp. scale used to measure extreme
  • (1.) 0 Kelvin -273?C or -460?F
  • (2.) Absolute Zero or 0 Kelvin (K)
    molecules have the lowest KE possible.

  • IX. Energy Transfer-three types
  • A. Conduction
  • B. Convection
  • C. Radiation
  • X. Energy Transfer Within a body
  • A. Conduction molecules transfer energy
    by physical (direct) contact.
  • 1. Solid molecules easily make
    contact because they are close together.
  • 2. Solids are good conductors of heat.
  • 3. Liquids are poorer conductors of heat
    because molecules are farther apart.
  • 4. Gases are the poorest heat conductors
    because molecules hardly ever make contact.

  • B. Convection molecules transfer
    energy by carrying it from one place to
    another (Ex liquids and gases when heat
  • 1. Gas liquid molecules transport energy
    if movement is unrestricted.
  • 2. Air is not a good conductor, but it is
    ideal for convection. Hot air
    rises by convection.
  • 3. Convection currents-streams of hot air
    (ideal for gliding) or streams of
    warm water (in the ocean).

  • XI. Energy Transfer Between bodies
  • A. Conduction between bodies molecules in
    one body contact molecules in another body and
    transfer energy. (Ex Hot soup to a spoon in
    the soup).
  • B. Radiation Energy transferred without
    direct contact. (Ex suns or light rays)
  • 1. When radiant energy is absorbed, molecules
    move faster temp. rises.
  • 2. Infrared radiation (invisible light) all
    objects give off some amount of this
    type of radiant energy.
  • 3. Some hot objects give off radiation in the
    form of visible and invisible light (Ex
    hot stove-light is seen and heat is felt).
  • C. Note energy transfer between bodies
    occurs by conduction radiation.

  • XII. Insulators make energy transfer difficult
  • A. Insulation against conduction
  • 1. Makes molecular contact difficult.
  • 2. A poor conductor (air) makes a good
  • 3. Examples
  • a. Styrofoam pockets of air limit
  • b. Space shuttle tiles help shuttle
    withstand heat from re-entry to Earth.
  • c. Fur / feathers trap air for insulation.

  • B. Insulation against convection
  • 1. Stops molecular movement from one place
    to another.
  • 2. Examples windows, doors,
  • C. Insulation against radiation
  • 1. Block light rays.
  • 2. Examples
  • a. Light or shiny materials reflect
  • b. Dark or dull materials absorb
  • c. Ozone insulates Earth from UV rays
    by absorbing them.
  • D. Insulation limits transfer of energy
    between bodies. Ex Wet suits limit energy
    transfer from a warm body to the cold water.
  • E. Insulation limits transfer of energy
    within a body. Ex Windows limit energy
    transfer from warm to cold air.

  • XIII. Heat vs. Temperature
  • A. Heat the amount of energy transferred
    between 2 groups of molecules at different
  • B. Temperature the measure of motion
    (KE) of a typical molecule within a body
    of matter.
  • C. Heat Flow
  • 1. Heat flows from a higher temperature
    body to a lower temperature body.
  • 2. Heat flows between objects in contact
    ONLY when a difference in temperature exists.
  • 3. If 2 hot objects come into contact,
    heat will NOT flow between them IF they have
    the same temperature.

  • D. Specific Heat the amount of heat required
    to change a unit mass of a substance by one
    degree of temperature. (The amount of heat
    needed to change temperature by a certain
  • 1. How difficult something is to heat or to
  • 2. A long heating time indicates a long
    cooling time.
  • 3. Substances with a high specific heat are
    harder to heat. (Ex water)
  • 4. Substances with a low specific heat are
    easier to heat. (Ex silver)
  • E. Remember Energy lost Energy gained (Law
    of Conservation of Energy)

  • XIV. Calculating Heat Energy
  • A. Heat can be measured in calories or joules
    ( 1 cal 4.18 J ). A nutritional calorie
    1 kcal Calorie.
  • B. Remember specific heat (heat capacity)
    has to do with the ability to absorb heat
  • C. Formula Heat (J of energy gained/lost)
    mass (grams) x change in temp(?C) x
    specific heat (J/g?C)
  • H m x ?T x Cp

  • XV. Heat / Phase Change
  • A. Phase change occurs when
    substances change state.
  • B. Phase changes require energy. As
    more heat is added, temperature does NOT
    increase, instead that thermal energy goes
    into breaking the bonds as it changes
    state. (See graph at )
  • C. Heat of fusion solid to a liquid.
  • D. Heat of vaporization (liquid to a gas).
  • E. Refer to graph.

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  • XVI. Earth Science Applications
  • A. Sun Energy-air/water patterns /
    relationships 1. Differences between
    climate and weather
  • 2. Global climate/warming, greenhouse effect
  • El Nino, La Nina, and other climatic trends.
  • Temperature effects on ground water

  • B. Earths internal structure (core, mantle,
  • 1. Convection as mechanism for plate tectonics
  • 2. Geological manifestations (plate tectonics,
    earthquakes, volcanoes, mountain building)
  • 3. Impact on society
  • C. Characteristics/Evolution of Earth in terms
    of age (rock sequences, fossils,
    relative/radiometric dating) and the geosphere,
    hydrosphere, atmosphere, and biosphere
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