Insulation properties, scientific theory heat can be transferred in three ways, either through conduction, convection or radiation.

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Insulation Properties

Scientific Theory

        Heat can be transferred in three ways, either through conduction, convection or radiation.

        Convection is when warm water or gas rises and as a result is expanded.  As it is expanded it is less dense than the cold water or gas.  The cooler water or gas is therefore denser now and so falls to the bottom and is heated; the same process is reciprocated as described above.

        Objects are always taking in and giving out radiation.  The amount of radiation given out depends on the temperature and the surface area.  A dull black surface loses energy more quickly and is therefore said to be a good radiator.  In comparison to this a bright shiny surface is a poor radiator.

A dull black surface is a good absorber of radiation, which means it takes in and gives out radiation quite easily.  The exact opposite to this is a poor absorber of radiation i.e. a bright shiny surface.  This is because they reflect the infra-red rays, (rays, which cause the most heating).

It is also important to remember that that the hotter the object i.e. the higher the temperature the more energy it radiates.

        When an object is heated the heat energy is conducted from the side which is being heated to the cold end.  This energy is transferred to the other end through atoms.  The atoms at the hot end vibrate more and more as they are being heated, this vibration is passed on to the other atoms.  It is evident now that metals are good conductors.  This is because they have many free electrons that move around the metal and transfer the heat energy.

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Insulation is quite the opposite of conduction.  It doesn’t have many free electrons to transfer the heat energy.

The question is that why are some materials conductors and some insulators?

The table below explains the answer.

From the above table we can see than insulators cannot conduct because in each mm  there is only about one electron which is free to move.  The rest of the electrons are firmly fixed to their atoms.

Prediction

To help me predict the best insulator, I used the table below of the insulation of houses as ...

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