Post on 14-Jan-2015
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CONDUCTIONCONDUCTIONConductors And Insulators
From the list of materials listed, which is the best
insulator and which is the worst insulator? And Why?
1.Air2.Vacuum
3.Glass
24th. Nov. 09
Learning ObjectivesLearning Objectives
1. To know why some 1. To know why some materials are good materials are good
insulators and others are insulators and others are not.not.
2. To know that metals 2. To know that metals are good conductors and are good conductors and
non-metals are poor non-metals are poor conductorsconductors
Key wordsKey wordsConductors, InsulatorsConductors, Insulators
Kinetic EnergyKinetic EnergyElectrons, AtomsElectrons, Atoms
BondsBonds
Investigating Investigating Conductivity Using Conductivity Using different Materials different Materials
(Metals and Non-metals) (Metals and Non-metals) page 232page 232
Bunsen Flame (Teacher Demonstration)
Recap States Recap States of Matterof Matter
Liquid-Solid and GasesDraw the particle arrangement in
each state of matter (S-L-G)Using your diagram explain why
gases are not good conductors of heat.
Particle Particle arrangement in S-L-arrangement in S-L-
GG
Solid Liquid Gas
What is the What is the difference in difference in
particle particle arrangement in arrangement in metals and non-metals and non-
metals?metals?
ConductionConduction
As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on
and so on, the vibrations are passed along the metal and so is the heat. We call this... Conduction
Particle Particle arrangement in arrangement in
Non-metalsNon-metals
Particles Particles arrangement in arrangement in
MetalsMetals
Metals are differentMetals are different
The outer _______ for metal atoms drift, and are free to move.
When the metal is heated, this ‘Sea of electrons’ gain _____ energy and transfer it throughout the metal.Insulators, such as ___ and ____, do
not have this ‘Sea of electrons’ which is why they do not conduct heat as well as metals.
electrons
kinetic
woodplastic
Conduction in Conduction in MetalsMetals
All metals are good conductors of electricity. For a similar reason, they are also good conductors of heat.
In metals, not only do the atoms vibrate more when heated, but the free electrons charge around more as well. These transfer the energy much faster than just vibrations in bonds.
Conduction in Non-MetalsConduction in Non-Metals
Every atom is physically bonded to each other in some way. If heat energy is supplied to one part of a solid, the atoms vibrate faster.
As they vibrate more, the bonds between atoms are shaken more. This passes vibrations on to the next atom, and so on:
Eventually the energy spreads throughout the solid. The overall temperature has increased.
Insulator are the Insulator are the opposite of opposite of
conductors. True conductors. True or False? Why?or False? Why?
(use traffic light to assess)(use traffic light to assess)
INSULATORS
Particle arrangement in Particle arrangement in Metals and Non-metalsMetals and Non-metals
Ask a volunteer to read Conduction in Metals
On page 233
Copy key point and answer Q1, Q2 and 3
Testing sheets of Testing sheets of materials as insulators materials as insulators
page 233page 2331. Use different materials to insulate identical
cans (or beakers) of hot water.2. The volume of water and its temperature at
the start should be the same.3. Use a thermometer to measure the water
temperature after the same time.
The result should tell you which insulator was best.
ResultsResultsMaterials Starting
temperature (degree Celsius).
Temperature after 300 s (degree Celsius)
Paper 40 32Felt 40 361. Which material was the best thermal insulator?2. Which variable shown in the table was controlled to make this a fair test.
PlenaryPlenaryWhat happen when you touch a metal?
And why.