# Energy / Thermodynamics (Heat) - PowerPoint PPT Presentation

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## Energy / Thermodynamics (Heat)

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### 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)

1
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
(gravitational/elastic)
• 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
conservation)
• 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
(Joules)

2
• 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
time.
• A. Calculated by P W/t
• B. Units are in watts (W) 1W1
Joule/second

3
• 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
conservation

.
4
• 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
• 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
temp.
• (1.) 0 Kelvin -273?C or -460?F
• (2.) Absolute Zero or 0 Kelvin (K)
molecules have the lowest KE possible.

5
• IX. Energy Transfer-three types
• A. Conduction
• B. Convection
• 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.

6
• B. Convection molecules transfer
energy by carrying it from one place to
another (Ex liquids and gases when heat
rises.)
• 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).

7
• 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
• 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

8
• XII. Insulators make energy transfer difficult
• A. Insulation against conduction
• 1. Makes molecular contact difficult.
• 2. A poor conductor (air) makes a good
INSULATOR.
• 3. Examples
• a. Styrofoam pockets of air limit
conduction.
• b. Space shuttle tiles help shuttle
withstand heat from re-entry to Earth.
• c. Fur / feathers trap air for insulation.

9
• B. Insulation against convection
• 1. Stops molecular movement from one place
to another.
• 2. Examples windows, doors,
weather-stripping.
• 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.

10
• XIII. Heat vs. Temperature
• A. Heat the amount of energy transferred
between 2 groups of molecules at different
temperatures.
• 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.

11
• 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
amount.)
• 1. How difficult something is to heat or to
cool.
• 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)

12
• 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
energy.
• 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

13
• 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.

14
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15
• 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

16
• B. Earths internal structure (core, mantle,
crust)
• 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,