C10: MATERIALS Flashcards
What is an alloy?
a mixture of a metal with small amounts of other elements
Steels:
-main metal
-other elements
-uses
-main metal: iron
-other elements: carbon (stainless steel - chromium and nickel)
-uses: cutlery, construction, cars
Gold alloys:
-main metal
-other elements
-uses
-main metal: gold
-other elements: silver/copper/zinc
-uses: jewellery
How many carats pure gold?
24 carat
How do you calculate the % of gold in an alloy?
(no. of carats/24) x 100
Brass:
-main metal
-other elements
-uses
-main metal: copper
-other elements: zinc
-uses: brass instruments, brass pins in plugs
Bronze:
-main metal
-other elements
-uses
-main metal: copper
-other elements: tin
-uses: statues, coins
What is corrosion?
the destruction of materials (esp metals) by chemical reactions with water/O2
What is rusting?
corrosion when iron or steel reacts with oxygen and water
What is the word equation for rusting?
iron + oxygen –> iron oxide
What needs to be present for rusting to occur?
water
What are the 2 methods of preventing corrosion?
-protective layer
-sacrificial protection
Protective layer:
-how it works
-examples
-acts as a barrier which stops it reacting with O2 and water
-examples: paint, oil, plastic, any less reactive metal
Sacrificial protection:
-how it works
-examples
-zinc often used to coat iron nails because it is more reactive so any water and O2 that comes into contact with the nail reacts with the zinc and not with the iron
-examples: any more reactive metal
Clay
-soft when dug up out of the ground so it can be moulded into different shapes
-when fired at high temps it hardens to form a clay ceramic
-ideal for making pottery and bricks
Glass (properties)
-transparent
-can be moulded when hot
-brittle when thin
What are the 2 types of glass
-soda-lime glass
-borosilicate glass
How is soda-lime glass made?
-made by heating a mixture of limestone, sand and sodium carbonate
-when mixture cools it comes out as glass
How is borosilicate glass made?
-made by heating a mixture of sand and boron trioxide
-when mixture cools it comes out as glass
What are composites?
a material made from two or more different materials with contrasting properties
What are the components of composite materials?
-the reinforcement (fibres/fragments of a material)
-the matrix (acts as a binder and holds reinforcement together)
What are some examples of composites?
-fibreglass
-carbon fibre
-concrete
-wood
Fibreglass:
-reinforcement
-matrix
-properties
-uses
-reinforcement: glass fibres
-matrix: polymer
-properties: low density, very strong
-uses: skis, boats, surfboards
Carbon fibres:
-reinforcement
-matrix
-properties
-uses
-reinforcement: carbon fibres/nanotubes
-matrix: polymer
-properties: strong, light
-uses: aerospace, sports car manufacturing
Concrete:
-reinforcement
-matrix
-properties
-uses
-reinforcement: aggregate (mixture of sand and gravel)
-matrix: cement
-properties: very strong
-uses: building (eg: pavements/in skate parks)
Wood:
-reinforcement
-matrix
natural composite
-reinforcement: cellulose fibres
-matrix: organic polymer
What are the 2 factors that influence the properties of a polymer?
-how it is made
-what it is made from
What do the properties of poly(ethene) depend on?
-reaction conditions
-use of a catalyst
How is low density (LD) poly(ethene) made?
-made from ethene
-moderate temp
-high pressure
What are the properties and uses of LD poly(ethene)?
-low density
-flexible
-used for bags and bottles
How is high density (HD) poly(ethene) made?
-made from ethene
-lower temp
-lower pressure
-catalyst present
What are the properties and uses of HD poly(ethene)?
-high density
-more rigid
-used for water tanks and drainpipes
The _________ that a polymer is made from determine the type of ______ that form between the polymer chains. these _____ _____ between the different molecule chains determine the _______ of the polymer
the monomers that a polymer is made from determine the type of bonds that form between the polymer chains. these weak bonds between the different molecule chains determine the properties of the polymer
What are the 2 different types of polymers?
-thermosoftening polymers
-thermosetting polymers
Thermosoftening polymers
-melt when heated
-weak intermolecular bonds between polymer chains
-can be remoulded
Thermosetting polymers
-do not melt when heated
-strong covalent bonds form cross links between polymer chains
-when heated, cross links do not allow the chains to separate
-cannot be remoulded
