Heat,
Temperature, and
Review
Thermal Energy
• Total potential and kinetic energy associated
with the random motion and arrangement of
the particles of a material!
–Not concerned with the kinetic energy
of the object itself!!
Heat
• Thermal Energy that is absorbed, given
up, or transferred from one substance to
another.
– It is thermal energy on the move!!
Temperature
• Measure of the average kinetic energy of the
particles in a sample of matter!!
Relationship between Heat and
Temperature:
Which beaker is hotter?
Which beaker gives off more
heat?
80 oC
80 oC
Which
could melt
more ice?
Temperature is the same, amount of heat is different!!
Which has a higher temperature?
10 oC
30 oC
A
B
50 oC
80 oC
C
D
Which gives off more heat?
10 oC
A
10 oC
B
10 oC
C
10 oC
D
Heat Flow
• Heat always flows from a substance with a
high temperature to a substance with a low
temperature even if lower temperature
substance has more thermal energy!!
Which direction will heat flow?
A. A to B
B. B to A
C. Neither
D. Both A to B and
B to A
In which choice will heat flow fastest
from Y to X?
A
B
C
D
In which choice will heat flow fastest
from X to Y?
A
B
C
D
Specific Heat
• Heat required to change the temperature of a
substance.
• Different substances have different specific
heats.
– They conduct heat at different rates!!
– Consider Sand and Water!!!
– Think about the beach!
– Land breezes and Sea breezes!!
Specific Heats of some common
substances:
Substance
Specific Heat (J/g oC)
Water
Iron
Lead
Silver
Copper
Aluminum
Alcohol
Mercury
Platinum
Ammonia
Zinc
4.18
.450
.13
.245
.390
.900
2.43
.14
.13
4.71
.39
The higher the specific
heat, the more heat
required to change
temperature!!
Things with high
specific heats take a
long time to heat up
and a long time to cool
down!!
Things with a low
specific heat, get Hot
fast, but also cool fast!!
Heat required to change the
temperature can be determined by:
Where:
Q = heat energy in Joules(J)
m = mass in grams(g)
CP = Specific Heat Capacity(in J/g*oC)
DT = Temperature in oCelsius(oC)
Ex. How much heat is required to change
the temperature of a 250 g sample of
water from 15 oC to 60 oC?
Given:
m = 250 g
o
DT = 45 C
Cp = 4.18
Q = ???
Q = 250 g(4.18)(45 oC)
Q = 47,025 J
Ex. How much heat is required to change
the temperature of a 495 g sample of
copper from 60 oC to 240 oC?
Given:
m = 495 g
o
DT = 180 C
Cp = .390
Q = ???
Q = 495 g(.390)(180 oC)
Q = 34,749 J
Ex. How much heat must be removed
from a 210 g iron bar to reduce its
temperature from 150 oC to 25 oC?
A.
B.
C.
D.
16,536.5 J
11,812.5 J
9,450.5 J
5,480.5 J
Given:
m = 210 g
DT = 125 oC
Cp = .450
Q = ???
Q = 210 g(.450)(125 oC)
Q = 11,812.5 J
How does heat move
between substances:
• How many different ways are there to cook a
hotdog? 3
• Name them:
3 Ways to Cook a Hotdog!!!
Convection
Conduction
Radiation
3 Ways to Transfer Heat
1. Conduction---direct contact
2. Convection—transfer of heat in
liquids and gases!!
3. Radiation—transfer through empty
space!!
Conduction
Convection
Radiation
• Transferring Heat Energy Wst.
• Heat Equation Wst.