C15 Flashcards
What is corrosion
Corrosion is the destruction of materials by chemical reactions with substances in the environment.
Rusting is an example of corrosion.
Both air and water are necessary for iron to rust.
How can corrosion be prevented
Corrosion can be prevented by applying a coating that acts as a barrier, such as greasing, painting or electroplating.
Aluminium has an oxide coating that protects the metal from further corrosion
What is sacrificial coating
Some coatings are reactive and contain a more reactive metal to provide sacrificial protection, eg zinc is used to galvanise iron
What alloy is bronze and brass
Bronze is an alloy of copper and tin. Brass is an alloy of copper and zinc.
What metals are typically alloys
Most metals in everyday use are alloys
How is gold an alloy
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
How is steel an alloy
Steels are alloys of iron that contain specific amounts of carbon and other metals.
High carbon steel is strong but brittle.
Low carbon steel is softer and more easily shaped.
Steels containing chromium and nickel (stainless steels) are hard and resistant to corrosion
What is a characteristic of aluminium alloys
Aluminium alloys are low density
What is most the glass we use made from
Most of the glass we use is soda-lime glass, made by heating a mixture 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
How do the properties of polymers change
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
What are the different types of polymers
Thermosoftening polymers melt when they are heated.
Thermosetting polymers do not melt when they are heated
How are most composite materials made
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
Thermo softing nd setting ing tsructure
One has indvdual polymer chain intertwinded
One has moners which cross link the polymer chains
