1. Conduction

Conduction is the process of thermal energy transfer without any flow of the material medium

Conduction is the main mode of heat transfer in solids.

In conduction...
-heat is transferred from one atom to another by the vibration of atoms.
-heat is also transferred by the movement of free electrons from the hot end to the cold end, thus metals are good conductors of heat while liquids and gases are not.

How to reduce heat transfer by conduction
(heat loss)?
-Pockets of air trapped in materials such as wool, fibre, glass and expanded polystyrene reduce heat transfer.

eg.
wool-used as winter clothing to help reduce heat loss from the body to keep the body warm
fibre glass- used as insulation in roofs, between double-walls of buildings and in gas oven
expanded polystyrene[Polyurethane Foam]- used in walls of refrigerator to insulate the refrigerators, keeping the temperature in it low. It can also isolate hot items.

'Eureka' teaching about conduction.



Experiment



A crazy experiment showing on the principle of conduction.

When the match was over the balloon, thebflame touches the blown balloon and it burst.
However, when the second balloon was filled with water, and when the flame touches it, it did not burst.
And to make sure its true, the match was put over the second balloon at the part without water, it burst.

Why?
This is because water is a poor conductor of heat.
When the heat is tranferred to the balloon without water, just air, the heat burns the rubber and the air rushes out.
However, the balloon with water, the heat is transferred into the water, which is a poor conductor of heat, thus the rubber did not burn.