C15 - Using Our Resources - C15.1, C15.2, C15.3 Done Flashcards
What is corrosion of metals caused by?
Chemical reactions between the metal and other substances in the environment
What is rusting?
The corrosion of iron (and most steels)
What is the formula for rust and what is needed for its process?
Rust’s formula is Fe2O3, and rusting’s reactants are iron, water and oxygen
What is the word equation for the process of rusting?
Iron + Oxygen + Water ===> Hydrated iron(III) oxide
What are the two ways to prevent rust forming?
Sacrificial protection - getting a more or less reactive metal to react with the oxygen and water instead of the iron, and barrier protection - whereby the iron is covered by a physical barrier to stop the oxygen and water getting to it
How does sacrificial protection work?
The sacrificial metal is electroplated onto the object, or attached to it through dipping the object into it or through wires. When the oxygen and water are applied, they react with the sacrificial metal as it is easier to react with. One example of sacrificial protection is galvanisation - protecting iron with zinc
Where is sacrificial protection often used? (What kind of conditions?)
Sacrificial protection is often used in tough conditions where iron rusts easily, such as by the sea where the iron would be in almost constant contact with the seawater
Does the sacrificial metal also forever?
No, it must be replaced after some time as it reacts with the water and oxygen - and so would need replacing afterwards in order to remain the actual metal - not, for example, zinc xyz
Why are alloys needed for many pure metals?
As many pure metals such as aluminium and iron are relatively soft and early shaped, due to their lattice ionic structures with layers that can slide over each other. This means that they will just bend when put under pressure, rather than actually resisting
What is bronze an alloy of and when was it discovered?
Copper and tin, and it was discovered around 5500 years ago
Where is bronze often used, and what qualities mean that it is used there?
In ship’s propellers, and statues and decorative items. This is because it looks good, and is strong and resistant to corrosion
What is brass an alloy of?
Copper and zinc
Where is brass often used?
In instruments, door fittings and taps
What qualities does brass have?
Strong but workable
What can the different alloys of aluminium be used for? (From ….. to ….. )
From armour to aircraft, it has lightweight and heavier variants, all of which are strong
What is gold often alloyed with when making jewellery?
Copper
How is the purity of gold measured?
Through carats, if you divide the number of carats some gold is by 24, then you will get its percentage purity
What are carbon steels?
Carbon steels are alloys of iron and carbon (ranging from 0.03% carbon to 4%). They are cheap to make and are strong but brittle in high carbon concentrations, and malleable and weaker in low concentrations
Where are carbon steels used?
Car bodies, machinery, ships, containers and structural steel
What are stainless steels made of and what properties do they have?
They do not rust, they are strong and they are hard. They are made of iron with high percentages of chromium-nickel
What are nickel-steel alloys used for?
Long span bridges, bicycle chains, and military armour plating, as they are very resistant to stretching forces
What two factors do the properties of a polymer rely on?
The monomers used to make it, and the conditions chosen to carry out the reaction
What is the difference between the structures of high density and low density polymers?
Low density polymers are much more randomly arranged, with branches coming off branches and large and small pockets of space in between them, whereas in contrast high density polymers are more orderly in straight lines
What are thermosoftening polymers?
Polymers that melt and soften when they are heated. Their chains are often tangled rather than bonded
What are thermosetting polymers?
Polymers that do not melt due to strong covalent bonds the hold their chains together. At high enough temperatures, the polymer will just char rather than melt
