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Name: Max
Status: student
Grade: 6-8
Location: MD
Country: USA
Date: Winter 2009-2010



Question:
Why do insulators prevent the transfer of heat?


Replies:
Hi Max,

Remember that there are at least three ways in which heat can be transferred: conduction, convection, and radiation. When particles transfer kinetic energy by coming into contact with each other, the faster moving particle slows down and the slower particle moves faster, we call this process conduction. When faster moving particles migrate to areas where there are slower moving particles so that the average speed in the slow area increases, we call this convection. When heat is transferred through empty space by an object that is giving of energy in the form of waves (light), we call this radiation.

So, when an object is said to be an insulator, it is somehow able to stop one or more of these transfers of heat. A vacuum, or low pressure gas, is particularly good at limiting conduction because there are few particles that come into contact. A shiny surface does not allow light to penetrate into an object so it is particularly good at stopping radiation transfer. A solid object that does not flow or move so much at a molecular level may be good at stopping convections. So you can imagine that a vacuum inside a container that has a mirrored surface (such as what is inside those bottles that often hold hot liquids, like the thermos brand) are particularly good at being insulators since they tend to limit all forms of heat transfer.

Greg (Roberto Gregorius)
Canisius College



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