Transcript Energy and Specific Heat - Siverling
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
1 st Law of Thermodynamics Energy can’t be created or destroyed During any reaction, the total final energy is
the same as
energy the total initial
2 nd 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 1 o C in temperature Variable:
c
Units:
J g
°
C
The Heat Equation
E
=
mc
D
T
E = Heat energy m = mass c = specific heat Δ T = temperature change
Example 1
How much energy is needed to raise 10g of steel from 25 o C to 30 o C? (The specific heat of steel is 0.470
J / gC ).
D
T
= 30 °
C
25 °
C
= 5 °
C E
=
mc
D
T E
= 10
g
´ 0.470
E J g
°
C
= ´ 23.5
J
Example 2
How much energy is needed to raise 10g of wood from 25 o C to 30 o C? (The specific heat of wood is 2.500
J / gC ).
D
T
= 30 °
C
25 °
C
= 5 °
C E
=
mc
D
T E
= 10
g
´ 2.500
J g
°
C
´
E
= 125
J
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 4.184
J / gC .
E
=
mc
D
T
180
J
= (1000
g
) ´ (4.184
J g
°
C
) ´ D
T
180
J
= (4184
J
°
C
) ´ D
T
D
T
= 180
J
4184
J
°
C
D
T
= 0.04
°
C
Example 4
A 12.6g piece of zinc was heated to 99.5
had dropped to 25.8
o o C. It was then added to a beaker with cooler water. When the water and metal came to thermal equilibrium, the temperature of the zinc C. The zinc transferred 586J of energy to the water. What is the specific heat of zinc?
D
T
= 99.5
°
C
25.8
°
C
= 73.7
°
C E
=
mc
D
T
586
J
586
J
= (12.6
g
) ´
c
´ 73.7
°
C
= (928.62
g
×°
C
) ´
c c
= 586
J
928.62
g
×°
C c
=
0.631
J g
°
C