Thermodynamics
If there was a thermometer attached to the
rubber band, what would you observe?
1
Thermodynamics
If there was a thermometer attached to the
rubber band, what would you observe?
The temperature goes up
2
Thermodynamics
If there was a thermometer attached to the
rubber band, what would you observe?
The temperature goes up
∆Q α ∆T
∆Q is the heat involved
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H EA T
U nits
T he unit on he at should be Joules, but often
pe ople use the c alorie , or k ilocalorie.
1 kc al = a m ount of he at re quire d to ra ise
1 kg of w ater by 1 degree C elcius.
1 kiloc al = 4.2 kilojoule s
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Thermodynamics
Heat
∆Q α ∆T
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Thermodynamics
Heat
∆Q α ∆T
6
Thermodynamics
Heat
∆Q α ∆T
or ∆Q
= (slope) m ∆T
∆Q
m∆T
7
Thermodynamics
Heat
∆Q α ∆T
∆Q
Water
or ∆Q
= (slope) m ∆T
NOTE: Equal masses
Iron
m∆T
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H EA T
4.2 kJ =
a m ount of he at re quire d to ra ise
1 kg of w ater by 1 degree C elcius.
T here fore , for w a te r the slope is
kJ
4.2
o
kg- C
9
Thermodynamics
Heat
∆Q = (slope) m ∆T
The slope of this graph is called the specific heat capacity. For
water, the specific heat capacity is
4.2 kj/kg-oC
10
Thermodynamics
Heat
∆Q = (4.2 kj/kg-oC ) m ∆T
How much heat is required to raise the temperature
of 10 kg of water by 20 oC?
11
Thermodynamics
Heat
∆Q = (4.2 kj/kg-oC ) m ∆T
How much heat is required to raise the temperature
of 10 kg of water by 20 oC?
Heat = (4.2 kj/kg-oC ) (10 kg) (20 oC)
= 840 kj
12
Thermodynamics
Heat
∆Q = (slope) m ∆T
∆Q
Water
NOTE: Equal masses
Clay, Marble
m∆T
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H EA T
Q ue stion: W ate r has a high spe cific h eat
c apac ity. W h en h eat is ad de d or re m ove d
from w ater , w ill this p rod uc e a r elative ly
large or sm all c h ange in tem pe ratu re for
th e w ate r as co m p are d to, for e xam ple,
c lay?
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Thermodynamics
Heat
∆Q = (slope) m ∆T
∆Q
Water
NOTE: Equal masses
Clay, Marble
m∆T
15
Thermodynamics
Heat
∆Q = (slope) m ∆T
∆Q
Water
NOTE: Equal masses
Clay, Marble
m∆T
16
Thermodynamics
Heat
∆Q = (slope) m ∆T
∆Q
Water
NOTE: Equal masses
Clay, Marble
m∆T
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Thermodynamics
Heat
∆Q = (slope) m ∆T
∆Q
Water
NOTE: Equal masses
Clay, Marble
Small change
Large change
m∆T
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Thermodynamics
Heat
∆Q = (slope) m ∆T
The variation in temperature between day and night
on mars can be as much as 150 degree Fahrenheit,
while the variation in temperature on the earth is
far smaller. Why?
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