CONDUCTION <ul><li>Conductors And Insulators </li></ul><ul><li>From the list of materials listed, which is the best insulator and which is the worst insulator? And Why? </li></ul><ul><li>Air </li></ul><ul><li>Vacuum </li></ul><ul><li>Glass </li></ul>24 th . Nov. 09
Learning Objectives 1. To know why some materials are good insulators and others are not. 2. To know that metals are good conductors and non-metals are poor conductors
Key words Conductors, Insulators Kinetic Energy Electrons, Atoms Bonds
Investigating Conductivity Using different Materials (Metals and Non-metals) page 232 Bunsen Flame (Teacher Demonstration)
Recap States of Matter Liquid-Solid and Gases Draw the particle arrangement in each state of matter (S-L-G) Using your diagram explain why gases are not good conductors of heat.
What is the difference in particle arrangement in metals and non-metals?
Conduction 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
Metals 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 wood plastic
Conduction in Metals 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-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 opposite of conductors. True or False? Why? (use traffic light to assess) INSULATORS
Particle arrangement in Metals 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 materials as insulators page 233 1. 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.
Results 1. Which material was the best thermal insulator? 2. Which variable shown in the table was controlled to make this a fair test. Materials Starting temperature (degree Celsius). Temperature after 300 s (degree Celsius) Paper 40 32 Felt 40 36
Plenary What happen when you touch a metal? And why.