Heating Houses – Revision Pack (P1)
Energy Flow:
Heat energy will always travel from a hotter object to a colder object. When energy
moves (or flows) away from the hotter object, the temperature of that object
decreases – its heat does NOT decrease, its hotness does.
Measuring Temperature:
A thermogram used colour to show both hotter and
cooler temperatures. Hotter areas will be lighter colours
(yellow/white) while the cooler areas will be darker areas
(purple/black/dark blue).
The image shows this well, the hottest area is the flame,
and the cooler areas are the surrounding worktop. We
can infer that the pan has not been on the hob for very
long because it is blue (meaning it is relatively cool.
There is a big difference between temperature and heat:
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Temperature is measured on an arbitrary scale (which allows you to only
compare the values) and is a measure of how hot something is; it is measured
in degrees Celsius (oC)
Heat is a measurement of internal energy, and is measured on an absolute
scale (which allows you to compare values); it is measured in Joules (J)
NOTE – when the temperature of an object increases, its particles tend to gain more
kinetic (movement) energy.
Specific Heat Capacity:
Specific heat capacity is a property which all substances have. It is the amount of
heat energy needed to increase the temperature of 1kg (of the object) by 1oC. It is
measured in J/kgoC – it will differ from material to material.
When an object is heated AND its temperature rises, energy is transferred.
The equation for energy transferred by Specific Heat Capacity is:
Energy Transferred = Mass x Specific Heat Capacity x Temperature Change
An example question would be:
Calculate the energy transferred when 75kg of water cools from 97oC to 370C. The
Specific Heat Capacity of water is 4200J/kgoC.
Energy Transferred = 75 x 4200 x (97-37) = 18900000J OR 18900kJ
NOTE – You need to know that the Specific Heat Capacity of water is 4200J/kgoC.
Heating Houses – Revision Pack (P1)
Specific Latent Heat:
Specific Latent Heat is the amount of energy needed to boil of melt 1kg of a
material. It is measured in J/kg and differs for different materials and different
changes of state.
The equation for energy transferred by Specific Latent Heat is:
Energy Transferred = Mass x Specific Latent Heat
An example question would be:
Calculate the energy transferred when 6kg of water changes from solid to liquid at
0oC. The Specific Latent Heat of melting for water is 334,000J.
Energy Transferred = 6 x 334,000 = 2004000J OR 2004kJ
When an object is heated and changes state, energy is transferred but the
temperature of the object stays the same. This is because when the state of an
object changes, energy is needed to break bonds that hold the molecules together
– so any energy coming in is used to break bonds rather than increase or decrease
the temperature of the object.
In the graph above, when the water changes state (melting and boiling) the
temperature stays the same because the energy being transferred from the heat
source is used to break bonds.
Heating Houses – Revision Pack (P1)
Past Papers:
PPQ(1):
Heating Houses – Revision Pack (P1)
PPQ(2):
Heating Houses – Revision Pack (P1)
PPQ(3):
Heating Houses – Revision Pack (P1)
PPQ(4):
Heating Houses – Revision Pack (P1)
PPQ(5):
PPQ(6):
Heating Houses – Revision Pack (P1)
Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
Heating Houses – Revision Pack (P1)
PPQ(4):
PPQ(5):
PPQ(6):