over here ...
the weight prevents the ice form floating to the area in
which the water is heated
thus it doesnt melt even if the water above boils.
this shows water is a poor conductor of heat
BUTBUT.
this happens not because its a poor conductor. due to CONVECTION
inwhich the heat rises less heat will be found at the bottom and instead the denser and cooler particles would be found.
WARNING
the explanation in the diagram is WRONG
when a bunsen burner is lighted below a metal gauze, the gas only burns below the gauze and no flame is obtained above it .if the burner is lighter\d above the gauze the flame will be above it only.
therefore metal is a good conductor of heat as it conducts the heat of the flame rapidly away from where the flame is directed at. thus making sure the heat is equally distributed and the wire does not melt.
~ air is an insulato
1. when a match stick is held 3 or 4m away from the bunsen flame it does not light up
2. pockets of air trapped in amaterials such as wood, fibre glass, felt and expanded polysterene reduce heat by conduction. they are therefore used to make
1. woolen clothing and blankets
2.fibre glass for insulation in roofs and walls
3. expanded polysterene in the walls of refrigerator
vacuum is an insulator
1. in a thermal flask there will be a space of vacuum in between the walls of the flask inside. thus keeping the heat inside preventing heat loss due to its insulation properties
(diagram and full question will be shown in the viewer's content section )
** double wall things!!
these products have double walls inwhich reduces the transfer of heat between the inside and the outside of a room.
the air or vacuum between reduces or eliminates heat transfer
double glass --- walls
glazed windows
same thing!
