So taking a bite….this
happens…..which ingredient has
caused the problem and why?
P1 1.7 Specific heat capacities.
Learning Objectives
• Explain what specific heat capacity is.
• Use the equation for specific heat
capacity.
• Evaluate the use of materials according to
their specific heat capacities.
• If you give the same amount of heat to different type of
matters you observe that changes in their temperatures
are different.
• Given an equal amount of heat to metal spoons and
wooden spoons, metal spoon has greater change in its
temperature.
• These examples show that each matter has its own
characteristics to absorb heat.
• We call this concept as specific heat capacity of the
matters.
• It is the distinguishing property of matters.
• We show it with the letter “c” and give the definition of
it as, heat required to increase temperature of unit mass
1 ºC.
• On the contrary, heat capacity of the system is defined
as “heat required increasing the temperature of whole
substance” and we show it with “C”.
• E=m.c where m is the mass of the substance and c is
the specific heat of the matter.
The specific heat capacity
equation.
• E = m cΔT
Where
• E is the energy in Joules
• m is the mass of the material in kg
• c is the specific heat capacity of the
material (this will be given to you)
• Δ T is the change in temperature °C
Exam feedback ….in an exam you will be expected to be
able to re-arrange equations and put the quantity you need
to calculate on the left.
How much energy does a kettle transfer when it
heats up 1 kg of water from 10˚c to100 ˚c?
The specific heat capacity of water is 4200J/kg ˚c
E
=
m
x
c
x
Heat
mass
specific heat temp change
Transferred
capacity
378kJ = 1kg x 4200
x 90
Questions
1. A student heats 1kg block of aluminium
and a 1kg block of copper to 50 °C. Explain
which block will be storing the most
energy.
2. Why does it take longer to boil a kettle full
of water than one only half full?
3. Explain why stand- alone radiators are
filled with oil, instead of being filled with
air?
Questions
4. How much energy does it take to heat up
500g of lead by 30 °C ?
5. A washing machine heats 10kg of water for
each wash cycle. How much energy is
saved by washing clothes at 30 °C instead
of 50 °C ?
6. A storage heater contains 100kg of
concrete. 1800kJ of energy is transferred
to it. What is the temperature change of
the concrete?
The specific heat capacities of
some materials.
Material
Specific heat capacity
J/kg °C
Air
100
Aluminium
899
Concrete
900
Copper
390
Iron
450
Lead
130
Oil
540
Water
4200