1. Specific heat capacity
06/12/2018
Specific heat capacity
Objective
To be able to apply the relationship between the change in internal energy of a material and its mass, specific heat capacity and temperature.

2. Specific heat capacity
06/12/2018
Specific heat capacity
The specific heat capacity of a material is the amount of energy required to raise 1 kg of the material by 1 °C.
It can be used to work out how much energy is needed to raise the temperature of a material by a certain amount:
specific heat
Capacity
(J/kg°C)
temperature
Change
(°C)
Energy
(J) =
Mass
(kg) x x
Energy is measured in joules (J).
Mass is measured in kilograms (kg).
Temperature change is measured in °C.
Specific heat capacity is measured in J/kg°C.

3. specific heat Capacity (J/kg°C) temperature Change (°C)
Worked Example
The specific heat capacity of water is 4200 J/kgoC, how much energy is needed to increase the temperature of 0.6 kg of water by 80oC in a kettle?
SHC of water =4200 J/kg°C m=0.6kg Temp. change = 80oc
specific heat
Capacity
(J/kg°C)
temperature
Change
(°C)
Energy
(J) =
Mass
(kg) x x
Energy = x x 80
= J
= kJ

4. Eg 2: Steel has a SHC of 500J / kgoC.
If 25 kg is heated by 15 degrees, how much energy was required?
Eg 3: If 3 kg of wax is heated up by 12 degrees it takes 104,400 Joules. What is the SHC of wax?

5. Metal
Suppose a block of metal has been heated up. The block now stores this energy until it cools down.
A material with a high specific heat capacity needs more energy to heat it up, but can store more heat energy.
For example, water has a high SHC.
It takes a lot of energy to heat up, but once heated can give out a lot of heat.

6. Material Mass Temp drop (degrees) SHC A 3 4 300 B 2 500 C 1 8 D 5 200
Which of the following gives out the most energy ?
Material
Mass
(kg)
Temp drop (degrees)
SHC
j /kgoC A 3 4
300 B 2
500 C 1 8 D 5
200

7. SHC Questions
E = mc∆T
What is the energy required to heat 4kg of iron from 22°C to 50°C if SHC = 450J/kg°C?
2. What is the mass of lead (SHC = 126J/kg°C) that increases its temperature by 7°C when 3000J of energy is supplied? Rearrange the formula:
m =

8. Sand has a much lower SHC than water
An example …
On the beach, both the sand and the sea are heated by the Sun’s radiation for the same amount of time. So why does the sand burn you but not the sea?
Sand has a much lower SHC than water