thermal_expansion

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					Thermal expansion - demonstration experiments

To demonstrate thermal expansion using liquids is quite difficult because they do not expand
much. I would suggest that you use a large flask with a capillary tube sticking out. The
volume expansion of the liquid is then "magnified" by the movement up the narrow tube –
rather like a thermometer.

Other liquids that you could try are paraffin, turpentine, glycerol and all sorts of oils (motor oil,
sunflower oil, olive oil).

A few ideas about thermal expansion using the expansion of gases:
(a) any kind of pressurised gas canister will explode if heated over a fire and so can be very
dangerous
(b) the gas/air mixture in the cylinder internal combustion engine "explodes" and expands
when heated by a spark from the spark plug
(c) the air in a hot air balloon expands when it is heated so lowering its density and helping
the balloon to rise
(d) an inflated sunbed or rubber dinghy may explode if left in the sun for a long time
(e) a dent can be removed from a table tennis ball by putting it in hot water
(f) cakes "rise" because of the gas in them expanding
(g) Galileo's air thermometer works by the expansion of air
(h) racing car tyres are kept warm to make them expand and become firm. This raises the
cars slightly off the road
(i) when a bullet is fired the air behind it is heated rapidly by the explosion of the cartridge
and the bullet is forced up the barrel of the gun

and now some effect of solid expansion:

Telephone wires are hung up slack in the hot summer weather so that they do not pull the
telegraph poles over when they contract in the winter.
Bimetallic strip - this is made of two metals that expand by different amounts when heated
joined together. It is used in thermostats and fire alarms.
Concrete roads are laid in sections with soft pitch between the sections.
Girders in buildings and bridges are made with gaps at the ends.
Glass to be used in cooking has to be a low expansion type such as Pyrex otherwise it would
shatter as it got hot.
High-speed planes are warmed by air friction and so get longer
Old buildings can be held together by a metal rod fixed through them and joined to plates on
the walls
Rocks in deserts crack, bits fall off them and turn to sand in the end
Rivets are heated before they are put in place to hold two metal plates together