Flashcards in Using resources Deck (51):
What are ceramics?
Non-metal solids with high melting points that aren't made from carbon-based compounds
What are clay's properties?
It is a soft material so can be moulded into different shapes but when fired at high temperatures, hardens
What are the properties off glass?
It is transparent can be moulded when hot and can be brittle when thin
What is the difference between soda-lime glass and borosilicate glass?
Borosilicate has a higher melting point and it made of sand and boron trioxide whereas soda-lime glass is made of sand, limestone and sodium carbonate
What is a composite?
Made of one material embedded in another; fibres or fragments of a material are surrounded by a matrix acting as a binder
Give four examples of composite materials
Fibreglass (glass in a polymer matrix), carbon fibre (carbon fibres or nanotubes in a polymer matrix), concrete (a mixture of sand and gravel embedded in cement) and wood (cellulose fibres in an organic polymer matrix)
How is a low density polyethene made and what are it's properties?
Made from ethene at a moderate temperature under a high pressure and normally with a catalyst. It is flexible
How is a high density polyethene made and what are it's properties?
Made from ethene at a lower temperature with a different catalyst. It is more rigid
What is the difference between thermosoftening polymers and thermosetting polymers?
Thermosoftening: individual polymer chains entwined together and can be melted/remoulded
Thermosetting: monomers that form cross links between polymer chains, don't soften when heated, much stronger
What are the properties of ceramics?
Insulators of heat and electricity, brittle and stiff
What are the properties of composites?
Depends on the reinforcement and matrix/binder used to make them, which means that they have many different uses
What are the properties of polymers?
Insulators of heat and electricity, flexible and easily moulded
What are the properties of metals?
Malleable, good conductors of heat and electricity, ductile, shiny and stiff
Why are pure metals turned into alloys?
Their regular structure makes them too soft for many uses so by adding another element to the metal, the layers are disrupted, making it harder than the pure metal
Give four examples of alloys and their uses
Bronze (copper + tin) for medals/decorative ornaments, brass (copper + zinc) for things that need low friction e.g. tap, gold alloys for jewelry and aluminium alloys for aircraft (low density and hard)
Give the word equation for the corrosion (rusting) of iron
Iron + oxygen + water --> hydrated iron (III) oxide
Why does all the iron in an object eventually corrode if left to rust?
Corrosion only happens on the surface of a material, but as the rust flakes off, it leaves more ion available to rust again
How can you show that both air and water are needed to rust?
Putting an ion nail in a boiling tube with only water or only air will not rust, however putting it in a tube with both will result in it rusting
How can rusting be prevented?
Painting/coating with plastic, electroplating by using electrolysis to reduce metal ions onto an iron electrode (the layer of metal that is formed will corrode instead of the iron) and oiling/greasing
How can metals be protected by galvanism?
The object is sprayed with a coat of zinc, which is protective but if scratched, can act as a sacrificial metal
What are natural resources?
Anything that forms without human input; they include anything that comes from the earth, sea or air
What are renewable resources?
Resources which reform at a similar rate to or faster than we use them
What are finite resources?
Resources that aren't formed quickly to be considered replaceable e.g. fossil fuels, nuclear fuels, minerals and metals
What are the benefits and risks of mining metal ores?
Benefits: Useful products, gives jobs and brings money to the area
Risks: Bad for the environment, uses a lot of energy, scars the landscape, produces lots of waste and destroys habitats
What is sustainable development?
An approach to development that takes account of the needs of present society whilst not damaging the lives of future generations
What is bioleaching?
Bacteria are used to convert copper compounds in the ore into soluble copper compounds, spearating out the copper in the process. The leachate (solution produced) contains copper ions which can be extracted
What is phytomining?
Plants are grown in soil that contains copper, then once grown, are harvested, dried and burnt. The ashes contains soluble copper compounds from which copper can be extracted
Why is recycling metals important?
It uses much less energy than is needed to mine, conserves the finite amount of each metal in the earth and cuts down on waste being sent to the landfill
How can glass be recycled?
They can be reused with reshaping and they can be crushed, melted and reshaped. They can also be sued in different purposes such as insulating glass wool
What is a life cycle assessment?
It looks at every stage of a product's life to assess the impact it would have on the environment
What are the four stages in a life cycle assessment?
Getting the raw materials, manufacture and packaging, using the product and product disposal
What are the problems with using a life cycle assessment?
It is hard to give the effects of some pollutant a numerical value, they can be biased due to the person carrying out the assessment and selective LCA's can also be biased as they can be written to give a company positive advertising
What is potable water?
Water that has been treated or is naturally safe for humans to drink
What is the difference between pure and potable water?
Pure water contains only H2O molecules but potable water can contain many other dissolved compounds
What is filtration?
A wire mesh screens out large twigs and then gravel and sand beds filter out any other solid bits
What is sterilisation?
Water is sterilised to kill nay harmful microbes or bacteria by bubbling chlorine gas through it or by using ozone or ultraviolet light
Why are distillation and reverse osmosis not commonly used?
They need a lot of energy, meaning that they are very expensive and not practical for producing large quantities of fresh water
How is reverse osmosis used to treat sea water?
Salty water is passed through a membrane that only allows water molecules to pass through, leaving ions and large molecules trapped by the membrane
What sources produce waste water?
Home uses, agricultural systems and industrial processes such as the haber process
How is sewage treated?
It is screened (large bits of material are removed), stands in settlement tank, undergoes sedimentation, lighter effluent is removed from top, treated by biological aerobic digestion to break down organic matter, sludge from bottom is broken down by anaerobic digestion, methane gas is released, remaining sludge can be sued as fertiliser and chemicals can be added to water to make it safe
Why is sewage treatment more effective in areas with less fresh water?
It requires more processes than treating fresh water but uses less energy than the desalination of slat water
How are the reactants obtained when making ammonia?
The nitrogen is obtained from the air and the hydrogen comes from reacting methane with steam to form hydrogen and carbon dioxide
What are the conditions used in the haber process?
The reactant gases are passed over an iron catalyst, the temperature is 450°C and the pressure is 220 atmospheres
How is nothing wasted in the haber process?
The ammonia is formed as a gas, bus as it cools, it condenses into a liquid which is removed. The unused nitrogen and hydrogen are recycled back into the system to react again
Why is the temperature used in the haber process a compromise?
The forward reaction in the Haber process is exothermic, meaning that the yield is greater at lower temperatures, however the rate of reaction will be faster at higher temperatures, so 450°C is a compromise
Why is the pressure used in the haber process a compromise?
Higher pressure moves the position of the equilibrium towards the products due to how there are twice as many molecules on the left hand side. This means that a higher pressure gives a higher yield, however that can be expensive so 200 atm is a compromise
Why are NPK fertilisers used in farming?
If plants don't get nitrogen, phosphorus and potassium, their growth and life processes are affected. These elements can be missing from the soil if they have been used up by a previous crop. By using these, farmers can get a higher yield
Give the word equation of the reaction which produces ammonium nitrate
Ammonia + nitric acid --> ammonium nitrate
How is ammonium nitrate made in industry?
The reaction is carried out in giant vats, at high concentrations resulting in a very exothermic reaction. The heat released is used to evaporate water from the mixture to make a very concentrated ammonium nitrate product
How is ammonium nitrate made in the lab?
The reaction is carried out on a much smaller scale by titration and crystallisation. the reactants are at a much lower conc than in industry, so less heat is produced and is safer. After the titration, the mixture is crystallised to give pure ammonium nitrate crystals (not done in industry as is too slow)