C15 Using our resources Flashcards
what is rusting?
the corrosion of iron or steel
what conditions are needed for iron or steel to rust?
oxygen and water
what is the chemical name for rust?
ruse = hydrated iron (III) oxide
word equation for the rusting of iron
iron + oxygen + water -> hydrated iron (III) oxide
what is done to iron or steel to prevent them from rusting?
preventing water and oxygen from reaching the iron/steel by coating it with either:
- paint,
-a more/less reactive metal,
- oil or grease,
- plastic.
how does rust spread?
- rust forms,
- it is soft and flakes off the iron/steel,
- exposing more iron/steel to the oxygen and water,
- so more of it rusts.
what is sacrificial protection? why does it work?
sacrificial protection: coating iron/steel with a more reactive metal which reacts with the oxygen and water instead of the iron/steel itself, preventing it from rusting.
works because the more reactive metal has a stronger tendency than the iron/steel to give away electrons and form positive ions.
what is galvanisation?
coating iron/steel with zinc which is more reactive, so sacrificially protects it from rusting.
when is sacrificial protection often used?
- used under harsh conditions e.g. in seawater,
- protecting underground pipes,
- when coating is likely to be scratched, e.g. commercial wheelie bins
give 2 alloys that are made using copper and one other metal
- copper and zinc alloy makes brass,
- copper and tin alloy makes bronze.
which 2 metals is bronze an alloy of?
what is it used for? why?
BROCT
- bronze is an alloy of copper and tin,
- used for statues, decorative items, ship propellers,
- because of its toughness and resistance to corrosion.
what is steel?
an alloy of iron with carbon and/or other elements
which 2 metals is brass an alloy of?
what is it used for? why?
BRACZ
- brass is a alloy of copper and zinc,
- used for taps, musical instruments and door fittings,
- because it is hard but workable: can be hammered into thin sheets and pressed into shapes.
give a property of aluminium alloys
low density
why are copper, aluminium and gold often alloyed with other metals?
to make them harder
why is gold often alloyed with copper?
so that it wears away more slowly
what is corrosion?
the destruction of materials by chemical reactions with substances in the environment
how to measure the proportion of gold in an alloy
divide the carat number by 24: e.g. 24 carat gold is 100% (pure), 18 carat gold is 75% gold.
describe the difference between the properties of low and high carbon steel
low carbon steel: softer and more easily shaped
high carbon steel: strong and brittle.
uses of aluminium alloys
lightweight alloys: aircraft
other aluminium alloys: armour plating on tanks and other military vehicles.
what are stainless steels alloys of?
what are their properties?
stainless steels:
- alloys of steel with chromium and nickel,
- hard, strong, the only steels which are resistant to corrosion.
what are stainless steels often used for
and why?
- often used for reaction vessels,
- because they are hard and strong, so withstand high pressures and temperatures,
- and are resistant to corrosion, so withstand corrosive chemicals.
what do the properties of a polymer depend on?
- the monomers they are made from,
- the conditions of the reaction used to create it.
what is the difference between properties of thermosoftening and thermosetting polymers?
thermosoftening polymers melt when heated
whereas thermosetting polymers do not.