Energy in Thermal Processes
Heat
Calorimetry
Phase Changes
Heat and Internal Energy
• _______ _______, U, is energy of atoms
and molecules of a system
– Includes KE of translation, rotation, vibration
– Includes PE of chemical/electrical bonds
• ______, Q, is transfer of energy between
system and environment due to
temperature difference ΔT
Units of Heat
• Historically defined in terms of __________
_________ of object
– calorie (cal) – the energy necessary to raise the
temperature of 1g of water from 14.5°C to 15.5°C
– British thermal unit (BTU) – the energy
necessary to raise the temperature of 1 lb of
water from 63°F to 64°F
• Heat (like work) is a transfer of energy and
has SI units of ________
1 cal  4.186 J
Specific Heat
• Every substance
requires a ________
amount of energy per
unit mass to change T
by 1°C
• Characterize the
material by its _______
heat c
• Units are J/(kg∙°C)
• See Table 11.1, p. 355
Q
11.2
c
mT
Q  mcT
T  T f  Ti
Calorimetry
• Use containers that are good ________
(no energy leaves/enters the container)
• Put warmer and cooler materials in
container
• Apply conservation of ______ Qcold  Qhot
In general
Q
k
0
Sign of ____ takes care of sign of Q
Latent Heat and Phase Change
• Sometimes energy transfer results in
changes of ____ (melting/freezing = _____,
boiling/condensing = _________)
• _____________ does not change
• Characterized by latent heat L
• See Table 11.2, p. 360; units are J/kg
Q  mL
11.6
Use + if ______ energy, – sign if _______ energy
Example: Ice to Steam
Q  mLv
Q  mcsteamT
Q  mcwater T
Q  mL f
Q  mciceT
Fig. 11.3, p. 361