C15 - Using our resources (Part 1 - Corrosion, Alloys, Ceramics and Composites, Polymers) Flashcards
What is corrosion
Corrosion is the destruction of materials by chemical reactions with substances in the environment
What is rusting
A corrosion process where ONLY iron or steel reacts with BOTH water and oxygen
How to set up the rusting experiment
- Set up 3 test tube
- First test tube with distilled water open to air
- Second with boiled water (removes O2) with a layer of oil over it
- Third with anhydrous calcium chloride (removes water) and a bung to stop water vapour entering
Methods to prevent corrosion
- Paint
- Oil/grease
- Electroplating w/ aluminium which forms aluminium oxide
What is galvanising and what does it do
- Coating a metal with zinc
- Zinc is more reactive so corrodes instead through SACRIFICIAL PROTECTION
- Acts as a barrier against water and oxygen
What is sacrificial protection
A more reactive metal than steel or iron placed over it so it oxidises before the steel/iron and prevents it from rusting
What is an alloy
A metal that have small amounts of another metal or carbon added
What is bronze an alloy of and what are its uses
- Mixture of copper and tin
- Used to make statues and bells
What is brass an alloy of and what are its uses
- Mixture of copper and zinc
- Used to make musical instruments and door handles
Properties and uses of aluminium alloys
- Low density but strong
- Can be used for aeroplanes and armour plating
- Also used for OVERHEAD CABLES
What metals are in gold alloys and what are they used for
- Gold is alloyed with silver, copper and zinc
- Used for jewelery
What is used to measure the proportion of gold in an alloy
Carats e.g. pure gold is 24 carats
Properties and uses of low carbon steel
- Soft + easily shaped
- Used to make car bodies
Properties and uses of high carbon steel
- Strong but brittle
- Used in construction and cutting tools
What is stainless steel an alloy of and what are its properties and uses
- Iron alloyed with chromium and nickel
- Hard and resistant to corrosion
- Used for cutlery
What is soda lime glass used for and how is it made
- Made by mixing sand, sodium carbonate and limestone(calcium carbonate)
- This is then heated in a furnance
- It cools into any intended shape
- Used for windows, wine glasses etc.
How is borosilicate glass made
- Made by melting a mixture of sand and boron trioxide
Properties and uses of borosilicate glass
- High melting point
- Used in kitchenware and labware
How are clay ceramics made
- Clay found in ground
- Clay is wettened and shaped
- It is put in a high temp. furnace and heated
How are composites made
- You get a reinforcement which is small fibres or fragments of a material
- The reinforcement is surrounded by a maxtrix or binder material
- This means composites have different properties that the materials in them
Examples of composites
- Carbon fibre - strong and light
- Reinforced concrete
- Plywood + MDF
- Fibreglass
What does the properties of a polymer depend on
- The monomers they are made from
- The conditions used to make the polymer
Things to change in order to change the properties of the polymer
- Reaction temperature
- Reaction pressure
- Catalyst
What happens when you heat and cool a thermosoftening polymer
- They melt allowing reshaping (+recycling)
- They go back to a solid when cooled
Structure of a thermosoftening polymer
Randomely tangled polymer chains with weak intermolecular forces
These break under heat, melting the substance
What happens when you heat a thermosetting polymer
They burn and this means they can’t be recycled or reshaped
Structure of a thermosetting polymer
- Strong covalent bonds (cross links) between polymer chains
- Bonds just as strong as the ones between monomers
- This means only when the polymer breaks will the cross links break leading to burning
