Energy and Specific
Heat
By: Sage Marshall
The Coolest Dude Ever
Heat
Heat – energy due to temperature
Measured in
-Joules (J)
-Calories (cal)
Heat
-Heat flows between objects
-Temperature is a property of objects
1st Law of Thermodynamics
Energy can’t be created or
destroyed
During any reaction, the
total final energy is the
same as the total initial
energy
2nd Law of Thermodynamics
Energy flows from a higher temperature to a
lower temperature
Specific Heat
Let’s think back to the example with
wood and hot metal.
-If I input the same amount of energy,
will both substances heat up to the
same final temperature?
Specific Heat
Specific Heat
The amount of energy it takes to raise 1g
of material 1oC in temperature
Variable: c
Units:
J
g°C
The Heat Equation
E = mcDT
E = Heat energy
m = mass
c = specific heat
ΔT = temperature change
Example 1
How much energy is needed to raise 10g of steel from 25oC to
30oC? (The specific heat of steel is 0.470J/gC).
DT = 30°C - 25°C = 5°C
E = mcDT
E =10g ´ 0.470 J g°C ´ (5°C)
E = 23.5J
Example 2
How much energy is needed to raise 10g of wood from 25oC
to 30oC? (The specific heat of wood is 2.500J/gC).
DT = 30°C - 25°C = 5°C
E = mcDT
E =10g ´ 2.500 J g°C ´ (5°C)
E =125J
Example 3
On a sunny day, each square centimeter of the ocean absorbs
180 Joules of energy from the sun each hour. Assume all
the heat is absorbed in the first 10m of water, which has a
mass of 1000g. How much does the water temperature
increase? (The specific heat of water is 4.184J/gC.
E = mcDT
180J = (1000g)´ (4.184 J
180J = (4184 J
°C
180J
DT =
4184 J
°C
g°C
)´ DT
)´ DT
DT = 0.04°C
Example 4
A 12.6g piece of zinc was heated to 99.5oC. It was then added
to a beaker with cooler water. When the water and metal
came to thermal equilibrium, the temperature of the zinc
had dropped to 25.8oC. The zinc transferred 586J of energy
to the water. What is the specific heat of zinc?
DT = 99.5°C - 25.8°C = 73.7°C
E = mcDT
586J = (12.6g)´ c ´ 73.7°C
586J = (928.62g×°C)´ c
586J
c=
928.62g ×°C
J
c = 0.631
g°C