Page 59 - Science Class 06

Remember that gases diffuse very fast while thermometres because it is very sensi ve to
liquids diffuse a bit slower because the heat. Water is a bad conductor of heat, but

par cles of gases have enough space it is not a non-conductor.
between them which allows them to move Gases are generally bad conductors of heat.
freely. As for solids, they diffuse very li le It is for this reason that woollen clothes

because their par cles are arranged in rigid keep us warm during winter. Air gets
pa erns. trapped in the empty spaces between
We can detect the leakage of LPG due to its par cles of wool. It does not let the outer

diffusive property. If we put a drop of red cold pass through it to reach the body. At
ink in a glass of water, its par cles diffuse the same me, it does not let the body heat
with par cles of water slowly and the water escape out. As a result, the body remains
turns red. safe from the effect of cold weather.

Conduc vity

Conduc vity means behaviour of the
ma er and its forms (materials) towards

heat, electricity and magne c force. For
convenience, we shall study it under three
heads—conduc on of heat, response to
magnets and conduc on of electricity.

Conduc on of Heat
Woollen clothes neither let heat of body
You must have seen a pressure cooker, a go out nor let cold come into it.
frying pan and a baking plate in your Response to Magnets
kitchen. These vessels are made of different We know that magnets posses a rac ve
metals that are good conductors of heat.
force. Various materials respond to this
They take up heat at once and conduct it to
force in different ways and measures.
the food being cooked. But the handles of
Let us see how:
these vessels are made of other materials—
Place some awl-pins, plas c bu ons, paper
wooden and plas c handles protect us from
bits, copper fillings, small coins and wood
burning. The reason is that these materials
shavings on a table and bring a magnet near
do not take up heat easily and thus save the
each of these things in turn.
hands of the cook from being burnt. In

other words, wood and plas c are bad
conductors of heat.
So, solid materials can be good conductors

or bad conductors of heat.

As for liquids—oils, mercury, etc. are very
good conductors of heat. Mercury is used in Iron and cobalt are highly magne c.

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