Specific Heat Capacity

Specific Heat Capacity
“One cool judgment is worth a
thousand hasty counsels. The thing to
do is to supply light and not heat.”
Woodrow T. Wilson
28th President of the United States
“When you can't make them see the
light, make them feel the heat.”
Ronald Reagan
40th President of the United States
Quantity of Heat
Heat energy (thermal energy) is measured in units
called Joules (symbol: J).
Barbecues often quote their heat energy output in
terms of British Thermal Units (btu).
1 J = 1055 Btu
This Napoleon Grill can
produce 74,000 Btu
(or about 70 J of heat
Amount of Heat Energy
The amount of heat energy in a substance depends
on several factors.
Temperature (measured in degrees Celsius, oC)
 Definition: The degree of hotness or coldness of a
body or environment (corresponding to its molecular
 the higher the temperature of a fixed amount of a
substance, the greater the heat energy present.
 Example: A full bathtub with 42° water has more heat
energy than a full bathtub with 20° water.
Amount of Heat Energy
The amount of heat energy in a substance depends
on several factors.
Mass (measured in kilograms, kg, or grams, g)
 Definition: A measure of the quantity of matter.
 the larger the mass, the greater the number of particles
with heat energy.
 Example: A full bathtub of 42° water has more heat energy
than a 1/2 of a bathtub with 42° water.
NOTE: 1 kg = 1000 g
Amount of Heat Energy
The amount of heat energy in a substance depends
on several factors.
Substance Specific Properties
 Different substances vary in their thermal properties.
 Example: When you eat a hot pizza, you burn your tongue
on the sauce not the crust.
 Example: A metal spoon in a pot of boiling water will warm
up faster than a wooden spoon in the same pot.
 This thermal property is called specific heat capacity, and
this also determines the amount of heat energy in a
Specific Heat Capacity
Heat is the energy that flows from one object to another
due to a difference in their temperatures.
When heat flows into an object its thermal energy
increases, as does its temperature.
Specific heat capacity is defined as the quantity
of heat energy needed to raise the temperature
of one gram of a substance by 1°C. Heat, like
other energies, is measured in the unit, joules (J). In
formula format specific heat capacity is:
Specific Heat Capacity
Substances with a low
specific heat capacity
warm quickly because
they need less heat
energy for a given
change in temperature.
They also give up their
heat quickly.
Substances with a high
specific heat capacity
take a long time to warm
up and they retain their
heat for a long time.
Specific Heat Capacity
Symbolically we represent the amount
of heat gained or lost as “Q”, the mass
involved as “m”, the temperature
change as “DT”, and the specific heat
capacity as “c”.
Based on our definition of Specific Heat
Specific Heat Capacity
This relationship is usually written as
Q  mc D T
Q = heat energy (in Joules, J)
m = mass (in grams, g)
c = specific heat capacity (in J / g • oC)
DT = Tf -Ti = temperature change (in oC)
The Specific Heat Capacity of
The specific heat capacity of water is
4.18 J / g • oC
This means that 4.18 J of heat energy are
required to increase the temperature of a
mass of 1 g of water by 1oC.