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Chapter 16 Temperature and Heat

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					Chapter 16:
Temperature
and Heat
Heat • Thermal energy that
     flows from something of
     high temp. to something
     of low temp.
      •Warm  Cold
      • Metric unit  Joules
      • Transfer of Thermal
      Energy.
    Temperature
•Measure of how hot or cold an
object is compared to a
reference point.
• Related to the kinetic energy
in an object.
• The faster the particles move
the higher the temperature.
   Temperature
•The reference point on the
Kelvin scale for temperature is
absolute zero.
•Absolute zero – a temperature
of 0°K.
   Thermal Energy
•Total Potential and Kinetic
Energy of an object.
•Depends on an objects mass,
temperature, and phase.
Thermal Energy vs. Temperature
 •Thermal energy is greater with
 an object with a greater mass.
 •Temperature is greater with an
 object whose particles are
 moving faster.
 •Coffee vs. Lemonade (475)
  Thermal Expansion
•Increase in an object’s volume
because of an increase in temp.
•It occurs because particles tend
to move farther apart as temp.
increases. Example: Balloon
•Gas expands more than liquids
and solids
         Specific Heat
• Heat needed to raise the temp.
of a 1g of an object 1o Celcius.
• Unique to every material
•The lower an object’s specific
heat, the more the temp.
increases when heat is absorbed.
• Water has a large specific heat

• Needs a lot of heat to
change its temp
•Heat is measured in Joules or
calories.
•One calorie is the energy the
required to raise the temp. of 1g of
water by 1C.
•One calorie is equal to 1.184 J
•The unit for specific heat is J/g C
  Q = m c ΔT


Heat mass specific change
           heat      in
                    temp.
Measuring Heat Changes
 •A calorimeter is an instrument
 used to measure changes in
 thermal energy.
 •It uses the principle that heat
 flows from hotter to colder
 objects until both reach the
 same temperature.
            Conduction
• Transfer of heat through direct contact.
•Conduction in gases is slower than in
liquids and solids.

                              or
Thermal Conductors
•Material that conducts
thermal energy well.
•Examples: copper &
aluminum pots & pans; wood
vs. tile flooring
Thermal Insulators
•Material that conducts
thermal energy poorly.
•Examples: air in a double pane
window, wood,
fiberglass, fat
     Convection
•Transfer of heat through
moving particles in fluids
(liquids & gases).
•Convection Current occurs
when a fluid circulates in a loop
as it heats and cools.
Example: oven
           Radiation
   • Transfer of heat by
   electromagnetic waves
   Examples: Heat from the sun, heat lamps
   used in restaurants

• light colored object  Reflect heat
• dark colored object  Absorb heat
 Thermodynamics
•The study of conversions
between thermal energy and
other forms of energy.
•3 Laws of Thermodynamics
       1st
       Law of
  Thermodynamics
•“Energy is conserved.”
•Energy is never created or
destroyed, and throughout a
conversion all of the energy can
be accounted for.
       2nd
       Law of
  Thermodynamics
“Thermal energy can flow from
colder objects to hotter objects
only if work is done.”
A heat engine is any device that
 converts heat into work.
Thermal energy that is not
 converted into work is called
 waste heat.
Waste heat is lost to the
 environment.
      3rd
      Law of
 Thermodynamics
•“Absolute zero cannot be
reached.”
•Scientist have cooled matter
almost to 0K, but have not been
able to cool it completely.
From his observations
of cannon drilling,
Count Rumford
concluded that heat
could NOT be a form
of MATTER
average kinetic energy of the particles of that
object?
4. As the temp of an object rises so does the
_______________.
5. Which device is based on the property of
thermal expansion?
6. Thermal energy depends on an objects
___________.
12. 1st law of thermodynamics says the amount of work
done by a heat engine equals the amount of __________.
13. Which law states that absoulute 0 can’t be reached.
14. What is a consequence of the 3rd law of
thermodynamics?
(read from the book)
15. What happens in a steam engine? (read)
16. What is a fluid that vaporizes and condenses inside
the tubing of a heat pump called?
(read) 2 questions about heat pumps on the test!
There will be fill in the blank questions with the following
word bank:
Word bank
conductor, compressor, phase, specific heat,
from, thermodynamics, degrees Celcius, zero,
vacuum, waste heat, convection, radiation,
conduction, less, greater, equal, temperature,
thermal expansion to, Kelvins, 1st law, 2nd law,
3rd law

Problem on specific heat

				
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