C15 Using Our Resources
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What is rust?
The corrosion of iron
what are the conditions needed for rusting?
air and water
what is the chemical name of rust?
hydrated iron oxide
how can rust be prevented?
• paint • oil/grease • plastic coating • less reactive metal • more reactive metal
what is sacrifical protection?
a method of preventing rusting where a more reactive metal than iron is attached or coated on an object
what does galvanised mean?
iron or steal objects that are protected from rusting by a thin layer of zinc metal on their surface
when is sacrificial protection used?
when the conditions are harsh such as in seawater
what accelerates rusting?
seawater
what is an alloy?
a mixture of two or more elements where at least one is a metal
why are alloys used?
it makes the metal harder this is because differently sized particles make it harder for layers to slip over each other
what are some alloys of copper and what are they made from?
• bronze (copper ant tin) • brass (copper and zinc)
why is gold alloyed and what is it alloyed with?
it is alloyed to make it harder it is usually alloyed with copper
what are steels?
alloys of iron with carbon and other elements
why is pure iron not used?
it is too soft to be usefull
how can you change the properties of steel?
carefully controlling quantities of carbon and other elements added to the iron
how are carbon steels made?
removing most of the carbon from the iron in the blast furnace
what are the properties of high carbon steels?
very hard but brittle
what are the properties of low carbon steels?
softer and more easily shaped
what are the substances in stainless steel?
chromium nickel iron
what are the properties of stainless steels?
resistant to corrosion
how can the properties of a polymer be altered?
• different monomers • the conditions of the reaction
what are the conditions to produce low density poly(ethene)?
high pressures a trace of oxygen
what is the structure of LD poly(ethene)?
the polymer chains are randomly branched and cannot pack closely together
what are the conditions to produce high density poly(ethene)?
catalyst 50 degrees C slightly raised pressure