topic 10 - Materials Flashcards
What does bronze consist of
Bronze is an alloy of copper and tin.
What does brass consist of
Brass is an alloy of copper and zinc.
What is Gold often alloyed with
Gold used as jewellery is usually an alloy with silver, copper and zinc. The proportion of gold in the alloy is measured in carats. 24 carat being 100 % (pure gold), and 18 carat being 75 % gold
Are aluminium alloys high or low density
Aluminium alloys are low density.
what is in soda lime glass
Most of the glass we use is soda-lime glass, made by heating a mix of sand, sodium carbonate and limestone.
Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than soda-lime glass.
how are clay ceramics made
Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating in a furnace.
polymers depend on
The properties of polymers depend on what monomers they are made from and the conditions under which they are made. For example, low density (LD) and high density (HD) poly(ethene) are produced from ethene.
differences between Thermosoftening and Thermosetting
Thermosoftening polymers melt when they are heated. Thermosetting polymers do not melt when they are heated
explain a composite material
Most composites are made of two materials, a matrix or binder surrounding and binding together fibres or fragments of the other material, which is called the reinforcement.
In some concrete buildings , the concrete is the matrix or binder and the reinforcement is in the steel or iron bars in the concrete
Properties of polymers
Generally, polymers are flexible, easily shaped, and good insulators of heat and electricity
LDPE
Conditions: Moderate temperatures, high pressure, catalyst
Properties: More flexible but weaker
Uses: Carrier bags
HDPE - high-density poly(ethene)
Conditions: Low temperature/pressure, catalyst
Properties: More rigid but stronger
Uses: Drainpipes
What is Corrosion
Corrosion is the destruction of materials by chemical reactions with substances in the environment. Rusting is an example of corrosion. Both oxygen and water are necessary for iron to rust.
Why does aluminium not rust
The aluminium oxide forms a protective layer when oxygen reacts with the outer aluminum , preventing further oxidation
give examples of sacrificial and barrier methods to prevent rusting
Barrier methods
Paint the iron (this works for large pieces of iron like ships)
Oil or grease it (this works when the object has moving parts, like a bike chain)
Electroplating (using electrolysis to cover the metal in another metal)
Sacrificial methods
Adding a more reactive metal to the iron, so that metal reacts with oxygen instead
Both - Galvanising - coating in zinc
Whats sustainable development
Sustainable development is an approach to human and economic development that meets the needs of the present generations, without compromising the ability of future generations to meet their own needs.
Comparisons between plastic and paper bags
Plastic bags use crude oil as raw materials BUT paper bags use wood
plastic bags require Hydrocarbons from fractional distillation and need to be cracked to form alkanes and they also go under polymerisation BUT paper bags require Timber to be pulped - High energy and waste
Plastic Bags can be reused multiple times BUT paper bags are single use
Plastic bags aren’t Biodegradable - taking lots of space in landfill and means it can make its way into the environment and harm animals BUT Paper bags are Biodegradable and non toxic
