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Describe temperature as a measurement of hotness

on an arbitrary or chosen scale.

temperature is a measurement of the

average kinetic energy of particles.

heat is a measurement of energy on an

absolute scale

Even though energy is still being

transferred, there is no temperature change when

materials are:

• boiling

• melting or freezing.

A substance must absorb heat energy so that it can melt or boil. The temperature of the substance does not change during melting, boiling or freezing - even though energy is still being transferred.

Recall that infrared radiation is:

• reflected from a shiny surface

• absorbed by a dull or rough surface.

Understand how absorption and reflection of infrared

radiation can be applied in everyday situations.

Explain how the property that air is a very good

insulator is used to keep homes warm:

• fibreglass, mineral or rock wool in loft insulation

• double glazing in windows

• insulation foam or fibreglass in cavity walls

• curtains at windows.

Describe other energy saving measures:

• reflective foil in or on walls

• draught-proofing.

energy is transferred by:

• conduction - transfer of KE between particles, to

include the role played by free electrons

• convection – how expansion when a liquid or

gas is heated causes a change of density which

results in (bulk) fluid flow

• radiation – infrared radiation is an electromagnetic

wave and needs no medium.

Simple ways to reduce heat loss include fitting carpets, curtains and draught excluders. It is even possible to fit reflective foil in the walls or on them.

Heat loss through windows can be reduced by using double glazing. These special windows have air or a vacuum between two panes of glass. If the double glazing has a vacuum there will be no conduction or convection. If the double glazing is made with air between the glass then convection is minimised because there is little room for the air to move. Air is a poor conductor so there will be very little heat loss by conduction.

Heat loss through walls can be reduced using cavity wall insulation. This involves blowinginsulating material into the gap between the brick and the inside wall. Insulating materials are bad conductors and so this reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection.

Heat loss through the roof can be reduced by laying loft insulation. This works in a similar way to cavity wall insulation.