C15 Flashcards
E. Rust?
iron + oxygen+water -> hydrated iron (111) oxide
Ways to prevent rusting?
- covering with:
paint, oil, grease or plastic ,a less reactive metal, a more reactive metal
D. Galvanised?
Iron or steel objects that are protected from rusting by a layer of zinc metal on their surface
D. Sacrificial protection?
An effective way to prevent rusting; a metal more reactive then iron (zinc or magnesium) is attached to or coated on an object
Corrosion of iron =
rusting
When is sacrificial protection often used?
- when coating is likely to be scrated
- in harsh conditions (eg. iron legs of a pier)
- underground pipes
How does sacrificial protection work?
Zinc is more reactive then iron, because is a stronger reducing agent, so it has a stringer tendency to loose electrons and form positive ions. so water/oxygen reacts with zinc instead of the iron.
Metals generally alloyed?
gold, copper and aluminium
Properties of high carbon steels?
very hard, very brittle
Properties of low carbon steels?
softer and easily shaped
Properties of stainless steels?
resistant to corrosion
What are stainless steels made of?
chromium-nickel steel
Properties of polymer depends on…
- monomers used to make it
- conditions used in the reaction
D. Thermosoftening polymers?
these soften easily when heated and then reset when cooled - as they are made of individual polymer chains that are easily seperated
D. Thermosetting polymers?
These do not melt when they are heated as they have strong covalent bonds between polymer chains
What happens to thermosetting polymers if they are very strongly heated?
they char
What is glass mainly made of?
Sand
Conditions used to make LD poly(ethene)
Very high pressures
Conditions used to make HD poly(ethene)
using a catalyst at 50 degrees and a slightly raised pressure
How is soda glass made?
by heating a mix of sand, limestone and calcium carbonate
What is borosilicate glass made from?
sand and boron trioxide
Borosilicate glass melting point?
higher then sode-lime glass
Properties of ceramics?
- brittle
- insulators
- hard
- resistant to chemical attack
How are ceramics made?
by forming shapes out of wet clay and then heating them in a furnace to about 1000 degrees
Type of bonds in ceramics
ionic and covalent
Structure of ceramics?
- ions and atoms form giant structures that form layers
- when wet, water gets in between layers making them slimy
- when heated in furnace, water is driven out and strong bonds form between layers
Why are ceramic brittle?
a sharp blow can distort the layers in the structure so that ions with like charges are adjacent and repel each other
D. Composites?
materials made of 2 or more different materials, containing a matrix/binder surrounding and binding together fibres or fragments of another material which acts as a reinforcement
Properties of composites of ceramics with polymers as binding material?
tough and flexible (fibreglass)
D. The Haber process?
way of turning nitrogen in air into ammonia - plants cant use nitrogen gas
Raw materials for production of ammonia?
nitrogen in the air
hydrogen - mainly from natural gas (which contains methane)
Conditions required for the Haber process?
- iron ctalyst
- high temperature ( about 450 degrees C)
- high pressure (about 200 atm)
what type of reaction is the production of ammonia?
reversible
How is ammonia collected?
the gases are cooled so that ammonia liquefies and the unused gases can be collected and reused
E. Haber process?
N2 (g) + 3H2 (g) –> 2NH3 (g)
Why arent higher pressures used in the Haber process?
Too expensive and danergous
Why arent lower temperatures used for the Haber process?
The rate of reaction would be too slow
How is hydrogen produced for the Haber process?
methane + steam –> hydrogen + carbon monoxide
What can ammonia be used for in its liquid form?
fertiliser
E. Ammonium nitrate fertiliser?
ammonia + nirtic acid ->ammonium nitrate
NH3 (aq) + HNO3 (aq) -> NH4NO3 (aq)
What is ammonia used to make?
Nitric acid
Ammonium sulphate fertiliser?
ammonia neutratlised with sulphuric acid
Ammonium phosphate fertiliser?
ammonia neutralised with phosphoric acid
Source of phosphorus?
Phosphate rock, which is mined and treated with acids to form fertiliser
Source of potassium?
potassium salts mined from ground for use in fertilisers
What do plants need for healthy growth?
nitrogen, potassium and phosphorus
D. Formulation?
a mixture that has been designed as a useful product
2 potassium compounds used in fertilisers?
potassium chloride
potassium sulfate
phosphate rock is mined and treated with acids to form compounds….
ammonium phosphate
calcium phosphate
