Using materials (10.3) Flashcards
What is corrosion?
The destruction of materials by chemical reactions with substances in the environment
What s an example of corrosion?
Rusting
What is necessary for iron to rust?
Both air and water
How can corrosion be prevented?
By applying a coating that acts as a barrier, such as greasing, painting or electroplating
Electroplating is the process of coating a metal with a thin layer of another metal by depositing it in electrolysis to improve the metal’s corrosion resistance
How is aluminium prevented from further corrosion?
It has an oxide coating that protects the metal
Describe sacrificial protection
Some coatings are reactive and contain a more reactive metal that will react with air and water before the less reactive metal to give it protection
What is an example of sacrificial protection?
zinc is used to galvanise (protect) iron
Most metals in everyday use are (…)
alloys
What is bronze?
an alloy of copper and tin
What is brass?
an alloy of copper and zinc
What is gold used in jewellery usually?
an alloy with silver, copper and zinc
as gold is very soft and malleable
What is the proportion of gold in the alloy is measured in?
carats
Describe 24 and 18 carat gold
24 carat - 100% (pure gold)
18 carat - 75%
What are steels?
alloys of iron that contain specific amounts of carbon and other metals
Describe the properties of high carbon steel
High carbon steel is strong but brittle
Describe the properties of low carbon steel
Low carbon steel is softer and more easily shaped/malleable (than high carbon steel)
What are stainless steels?
Steels containing chromium and nickel
What are the properties of stainless steels?
They are hard and resistant to corrosion (rusting)
Aluminium alloys are (…) density
low
so is light
What is bronze used to do?
To make coins
What is brass used to do?
to make musical instruments
What is a use of gold?
used in jewellery
What is a use of high carbon steels?
used in construction
What is a use of low carbon steels?
used for making car body panels
What is a use of stainless steel?
used for cutlery
What is a use of aluminium alloys?
Aluminium foil for storing/wrapping foods
as is malleable and light/low density
Which glass is the one we mostly use?
soda-lime glass
How is soda-lime glass made?
by heating a mixture of sand, sodium carbonate and limestone
What is borosilicate glass made from?
sand and boron trioxide
Borosilicate glass melts at (…) temperatures than soda-lime glass
higher
2 needed
What are examples of clay ceramics?
pottery and bricks
How are clay ceramics made?
by shaping wet clay and then heating in a furnace
can be a property as well
What do the properties of polymers depend on?
- what monomers they are made from
- the conditions under which they are made
Low density (LD) and high density (HD) poly(ethene) are produced from what?
Ethene
Describe thermosoftening polymers
polymers that melt when they are heated
(so can be recycled)
Describe thermosetting polymers
polymers that do not melt when they are heated
What is the difference in how LDPE and HDPE are made and their structure?
LDPE - formed at very high pressures with trace of oxygen, ethene forms LDPE - polymer chains randomly arranged
HDPE - using catalyst of 50oC and a sightly higher pressure - polymer chains branch less and so molecules line up more closely
Describe the structure of thermosoftening polymers
No covalent bonds between large molecules (chains), which are tangled together
so no cross links
So no/very weak intermolecular forces
so molecules can move over each other when heated and the plastic melts and are easily overcome
Describe the structure of thermosetting polymers
Strong covalent bonds forming ‘cross links’ between polymer chains
so strong intermolecular forces and held in position
so molecules only vibrate when heated, so are unable to move
What are most composites made from?
Two materials with different properties,
What are the components found in a composite?
a matrix or binder surrounding and binding together the reinforcement (fibres or fragments of the other material)
What is the reinforcement in a composite?
fibres or fragments of the other material
non-specification list
What are some examples of composites?
Which type of glass would be best to make a boiling tube in a school lab? Why?
Borosilicate glass would be best because it has a higher melting point than soda-lime glass.
This means that it will not melt when it is heated using a Bunsen burner.
3 needed
What are the physical properties of glass ceramics?
- transparent
- hard
- but is brittle (breaks easily)
2 needed
What are the physical properties of clay ceramics?
- resist compressive forces (can withstand weight and pressure)
- when wet can be shaped and then hardened at high temperatures
3 needed
What are the physical properties of polymers?
- poor conductors of heat and electricity, hence they are good thermal and electrical insulators
- LDPE for structures that require flexibility
- HDPE for structures that require rigid, strong structures to withstand pressure
useful for electrical wiring as they prevent overheating and an electric shock
1 for general property
What are the physical properties of composites?
- The properties of composites depend on the reinforcement and matrix used so composites can be tailor engineered to meet specific needs
- E.g. steel reinforced concrete has immense* tensile and compressive strength
What are shape memory alloys (materials)?
Alloys/materials that can be deformed when cold, but return to their original shape when heated
Give two reasons why wood is more sustainable than natural gas as a fuel
- Wood is renewable, natural gas is not
- Wood is carbon-neutral, natural gas is not
What is one property of a smart polymer that is different to that of an ordinary polymer?
has a shape memory
or
a smart polymer can return to original shape when conditions change
Give three properties of gold
is very soft
malleable
unreactive (so resists corrosion and stays shiny)
Cast iron is (…)
brittle
2 needed - 4 you could give
Catalysts have been developed to allow the reactions to occur at lower temperatures - why might this be of benefit to the manufacturer and environment?
- more product obtained (in shorter time)
- Less fuel costs
- Less pollution caused by burning fuels
- Using less fuel conserves energy resources
