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chapter 17: effects of heat and its transmission - Coggle Diagram
chapter 17: effects of heat and its transmission
expansion and contraction of matter
solids
when we pour boiling water too quickly into a cupof thick glass, the glass cracks
the solid glass on the inside exapands quickly than the outsde of the glass
liquids
the liquid mercury responds quickly to heat
the mercury level changes when the liquid is heated. this occurs occurs when the volume of the mercury changes
gases
when we bake a dough of bread, the dough rises
this is because the air bubbles trapped in the dough expands when heated.
effects of expansion and contraction
telephone wires and electricity cables
telephone wires and electricity cables raised on poles contract in cold water
they may become taut and even snap
wires and cables are hung loosely from pole to pole
tiled and concrete pavements
excessive expansion on very hot days can cause the cncrete to crack
tiles on the pavement may also pop out
expansion gaps are laid between these concrete slabs and tiles
this provides space for tiles and concrete slabs to expand without any damage
laboratry glassware
most of the glassware found in the laboratory are made of a special type of glass
glassware is less likely to crack when hot liquids are poured into it as the glass expands very lttle when heated
water pipes
expansion bends are made in oil and water pipes
this allows the pipe to expand without any damage
mrt and railway tracks
railway tracks can bend and twist due to expansion on hot weather
expansion gaps in the railway tracks provide space for the tracks to expand on hot days without any damage
bridges and metal girders
long bridges may expand up to one metre in hot weather
hence, these bridges need to be built with allowance for expansion
bridges and metal girders have expansion gaps or a free end resting on rollers
this allows the metal to expand without any damage on hot days
uses of expansion
opening a jar
putting the lid of a jar into warm water for a few minutes, causes the metal lid tp expand more than the glass jar, this loosens the lid and allows us to unscrew it easily