C15 Flashcards
E. Rust?
iron + oxygen+water -> hydrated iron (111) oxide
Ways to prevent rusting?
- covering with:
paint, oil, grease or plastic ,a less reactive metal, a more reactive metal
D. Galvanised?
Iron or steel objects that are protected from rusting by a layer of zinc metal on their surface
D. Sacrificial protection?
An effective way to prevent rusting; a metal more reactive then iron (zinc or magnesium) is attached to or coated on an object
Corrosion of iron =
rusting
When is sacrificial protection often used?
- when coating is likely to be scrated
- in harsh conditions (eg. iron legs of a pier)
- underground pipes
How does sacrificial protection work?
Zinc is more reactive then iron, because is a stronger reducing agent, so it has a stringer tendency to loose electrons and form positive ions. so water/oxygen reacts with zinc instead of the iron.
Metals generally alloyed?
gold, copper and aluminium
Properties of high carbon steels?
very hard, very brittle
Properties of low carbon steels?
softer and easily shaped
Properties of stainless steels?
resistant to corrosion
What are stainless steels made of?
chromium-nickel steel
Properties of polymer depends on…
- monomers used to make it
- conditions used in the reaction
D. Thermosoftening polymers?
these soften easily when heated and then reset when cooled - as they are made of individual polymer chains that are easily seperated
D. Thermosetting polymers?
These do not melt when they are heated as they have strong covalent bonds between polymer chains
What happens to thermosetting polymers if they are very strongly heated?
they char
What is glass mainly made of?
Sand
Conditions used to make LD poly(ethene)
Very high pressures
Conditions used to make HD poly(ethene)
using a catalyst at 50 degrees and a slightly raised pressure