Conduction
Temperature differences lead to the transfer of energy thermally by conduction, convection and radiation.
Conduction
- Conduction occurs in solids.
- Metals are good conductors.
- Non-metals and gases are usually poor conductors.
- Poor conductors are called insulators.
- Heat energy is conducted from the hot end of an object to the cold end.
Conduction in non-metals
If one end of a solid is heated, the particles of the solid gain Energy which an object possesses by being in motion. causing them to vibrate more. The All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. in a solid are close together and therefore the energy from the increased vibrations is passed on to the next atom, resulting in increased vibration for each subsequent atom. In non-metals, the process of conduction is slow.
Particles in a solid:
- can vibrate in a fixed position
- cannot move from place to place
Conduction in metals
The Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. in a piece of metal can leave their atoms and move about in the metal as free (or de-localised) electrons. The parts of the metal atoms left behind are now positively charged metal Electrically charged particle, formed when an atom or molecule gains or loses electrons.. The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons.
These move through the structure of the metal, colliding with ions as they go.
Image caption, Conduction in metal
A metal bar is heated up
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Investigating conductors
An experiment can be used to investigate which metal is the best conductor of heat. It involves some long thin strips of different metals (eg iron, aluminium and copper), wax, drawing pins and a Bunsen burner.
Method
- Fix the drawing pin to the end of the metal strip using drops of wax.
- Position the other end of the metal strip into a Bunsen flame.
- Record the time taken for the wax to melt and the drawing pin to drop off.
The shortest time shows the best conductor of heat.
Variables that affect the time taken for the drawing pins to fall include the distance they are from the flame and the thickness of the metal.
If you have controlled all of these variables, you should find that copper conducts better than aluminium, while aluminium conducts better than iron.