Transcript Chapter 12.1

Chapter 12.1
Temperature and Thermal Energy
What makes a hot body hot?
• In the 18th century scientists came up with
the caloric theory of heat
• In this theory an invisible substance called
“caloric” created heat.
• Only in the mid-nineteenth century did
scientists develop the kinetic-molecular
theory.
• This stated that as the particles moved
faster they created a greater kinetic
energy and thus heat.
Thermal Energy and Temperature
• According to the kinetic-molecular theory hot
bodies have a greater average thermal energy
than a cold body.
• Temperature is measured on a definite scale.
• Thermal energy is
proportional to the
number of particles in
the object,
while temperature
is not.
Equilibrium and Thermometry
• Temperature is measured using a process
called conduction.
• When your body and the thermometer are
at the same temperature they are at
thermal equilibrium.
• Thermometers contain a liquid that will
expand when heated and retract when
cooled, thus the liquid rises and falls.
Temperature Scales:
Celsius and Kelvin
• Each interval on the kelvin scale is called
a kelvin.
• A reading of 0oC is where water freezes.
• However, a reading of 0K is absolute zero.
• At absolute zero all molecules cease to
move.
• We have never been able to create
conditions of absolute zero.
Heat and Thermal Energy
• Heat is the energy that flows between two
objects due to a temperature difference.
• The transfer of energy through electromagnetic waves is radiation.
• The motion of fluid due to a temperature
difference is called convection.
• The specific heat of a material is the
amount of energy needed to change its
temperature
Specific Heat of Common
Substances
Material
Specific heat
Material
J/kg x K
Specific heat
J/kg x K
aluminum
903
lead
130
brass
376
methanol
2450
carbon
710
silver
235
copper
385
steam
2020
glass
664
water
4180
ice
2060
zinc
388
iron
450
Heat Transfer
• Q=mCDT = mC(Tfinal – T initial)
•
•
•
•
T= temperature (K)
m= mass (Kg)
Q= heat gained or lost (J)
C=specific heat (J/Kg*K)
heat transfer. Chart. Heart Transfer. N.p., n.d. Web. 11
Jan. 2011. <http://www.aos.wisc.edu/
~aalopez/aos101/wk5.html>.
heat transfer. Chart. Heart Transfer. N.p.,
n.d. Web. 11 Jan. 2011.
<http://www.aos.wisc.edu/
~aalopez/aos101/wk5.html>.