Using Our Resources Flashcards
Corrosion
Caused by chemical reactions between metal and substance in environment
Affect strength and appearance
Form of rusting
What is needed for rusting?
Both air and water for iron to rust
Preventing rusting
Paint Oil or grease Plastic Less reactive metal More reactive metal
Zinc in rusting
Protects iron Iron is galvanised Zinc is more reactive than iron Zinc has stronger tendency to form positive ions by giving away electrojs Zinc loses electrons = oxidised Zinc is sacrificed to protect iron
Magnesium or aluminium in rusting
Used instead of zinc in harsher conditions
Usually if in contact with sea water
What’s an alloy?
Mixture of metals
Copper alloys
Bronze = tine and copper = statues Brass = zinc and copper = Hard and workable
Aluminium alloys
Low density
Alloyed with side range of other elements
Lightweight
Armour plating on tanks
Gold alloys
Harder when alloyed
Gold usually alloyed with copper
Jewellery
Varying proportions of 2 metals gives different shades
Steels
Iron and carbon
Carbon steels
Removing most carbon from iron = using blast furnace
Carbon content decreases = cheapest steels made
High carbon = strong and brittle
Low carbon = soft and easily shaped, not as strong and less likely to shatter
Alloy Steels
Steels = expensive, contain high percentage of metals
Nickel steel alloys = bridges, resistant to stretching, operates well under hot conditions
Chromium-nickel steels = stainless steel, hard, strong, resistant to corrosion, cooking utensils and cutlery
Stainless steels = chemical industry, make vessels, expensive, withstand high temperatures and pressures
What do the properties of polymers depend on?
Monomers used to make it
Conditions chosen to carry out reaction
What are the 2 types of polyethenes
HD and LD
high density and low density
LD polyethene
Very pressures and trace of oxygen, ethene forms LD polyethene
Polymer chains randomly branched and cannot pack closely together = so have low density