Year 10 Term 3 Flashcards
what are finite resources
those being used up at a faster rate than can be replaced. if we carry on using at current rates they will eventually run out e.g. fossil fuels
what are renewable resources
those which can be replaced at the same rate as used
what is sustainibilty
developments that meet the needs of society without endangering future generations to meet their needs
alternative synthetic product for wool
acrylic fibers, polypropene
alternative synthetic product for cotton
polyester
alternative synthetic product for silk
nylon
alternative synthetic product for linseed oil
acrylic resin
alternative synthetic product for rubber
synthetic polymers (polybutadine)
alternative synthetic product for wood
PVC, composites (MDF)
why does rainwater contain minerals and microorganisms
rainwater dissolves some gasses in the air as it falls, then on the ground it dissolves soluble substances as it passes over them
why is rainwater acidic
some gases dissolved from the atmosphere are acidic (CO2, NO2, SO2) and when dissolved in rainwater will form acids lower on the pH scale
what is potable water
water that’s safe to drink without causing any health problems
how does the water treatment process work
water passed through filter made of sand, removes insoluble particles
passes through screen of metals bars stopping large objects
aluminium sulfate added clumping small particles together then dropping to bottom of tank
chlorine ozone added to steralise
pH of water checked then water stored
what is distillation
process of separating by heating and cooling
water is heated then evaporated leaving dissolved substances behind
the cooled, condensed and collected
ad’s and dis-ad’s of distillation
ad’s- in hot countries solar power used to heat water
dis-ad’s- high energy costs involved in heating water
what’s reverse osmosis
using semi-permeable membrane to separate dissolved substances
water placed under pressure to overcome natural osmotic pressure and water molecules can pass through membrane leaving solute behind
can remove 98% of dissolved salts
ad’s and dis-ad’s of reverse osmosis
ad’s- not heating required
dis-ad’s- energy needed to apply pressure, salt water corrodes the pumps
treating waste water
stage 1: screening
sewage screened to remove large materials and grit
stage 2: primary treatment
through sedimentation. heavy solids sink to the bottom-sludge. lighter effluent floats to the top
stage 3: secondary treatment
effluent removed and treated by biological aerobic digestion. this is where bacteria break down dry organic matter including microbes
stage 4: final treatment
sediment also broken down by anaerobic digestion. m,ethane gas produced which can be used as energy. remaining waste used as fertiliser
advantages of sewage treatment over desalination
methane produced as energy source
uses less energy so good for areas where there isn’t much fresh water
however people don’t like the idea of drinking sewage water
what is an ore
naturally occurring rock that contains enough metal or metal compound to make it economical to extract them
what is smelting
superheating ores to extract metal from ores
what is phytomining
some plants absorb metal compounds when they grow so plants burned and metal extracted from ash
what is bioleaching
some bacteria can live using the energy of the bond between sulphur and copper. this separates metal from ore. very energy efficient but very slow process
copper alloys
alloys of copper and tin are bronze. used to make statues and ship propellers as resistant to corrosion
brass is an alloy of copper and zinc. much harder than copper but still workable. makes musical instruments
gold alloys
usually alloyed with copper for jewelry to prevent wearing away
purity expressed in carats where 24 carats is 99.9% pure
aluminium alloys
low density metal, strong used to make aircraft
carbon steels
steels are alloys of iron containing specific amounts of carbon and other metals
high carbon steel strong but brittle
low carbon steel softer and more easily shaped
steels containing stainless steels are hard and resistant to corrosion.
polymerisation
double bond between 2 carbon atoms broken
another ethene monomer bonds to first one called additional polmerisation
branching occurs at high temps and and pressures
polyethene is then formed
what is the general formula for polmerisation
CnH2n
High density poly(ethene)
fewer branches
strong intermolecular forces
stronger polymers, more rigid
uses of high density poly(ethene)
plastic bottles, bottle caps, water pipes
low density poly(ethene)
more branched chains
weaker intermolecular forces
weaker polymers, more flexible
uses of low density poly(ethene)
plastic bags, plastic wraps, cable insulation
what is thermosoftening
melt when heated no cross links between chains weak intermolecular forces low melting points- tend to be flexible polymer chains tangled but not connected
examples of thermosoftening
poly(ethene), poly(propene), poly(vinylchloride)
what is thermosetting
don’t melt when heated
strong covalent cross-link bonding that doesn’t break on heating
high b.p so rigid
links between polymer chains
examples of thermosetting
vulcanised rubber, bakelite
what is corrosion
destruction of materials by chemical reactions with substances in the environment. rusting is an example
how does sacrificial protection work on small objects
metal can be coated in more reactive metal e.g. zinc which will corrode first, preventing the iron
this is galvanising
how does sacrificial protection work on large objects
large iron structures that are exposed to water and oxygen to large to be galvanised
blocks of more reactive metal attached to iron structures
zinc sacrificed to prevent iron from rusting
must be replaced before zinc dissolves
corrosion of aluminium
aluminium is very reactive and becomes oxidized quickly
al oxide layer isn’t crumbly like iron so thin layer acts as protective coating and al underneath stays intact for a long time
reduce
reducing the use of limited resources to make materials and energy
reuse
reusing products to reduce the production of new materials from limited resources
recycle
converting waste materials into new materials and objects
recycling metals
melting and recasting or reforming
amount of separation required depends on metal properties required for final product
recycling of aluminium
al most commonly recycled metal
when recycled only uses 5% of energy needed to extract from ore
most day-to-day aluminium you come across is at least 50% recycled
recycling of copper and gold/solver
copper recycled as it’s finite
silver and god recycled as hard to find
main source of recycled gold comes from computer component parts
why is it a problem to recycle alloys
because the alloys can’t always be separated
recycling glass
bottles can often be reused without reshaping
so can’t so are recycled. glass separated by colour and chemical composition
crushed then melted to be reshaped
for any product that’s made which stages are take into account when considering the life cycle of a product
extracting and processing raw materials
manufacturing and packaging
use and operation during its lifetime
disposal at end of useful like, including transport an distribution at the end of every stage
a life cycle assessment is carried out by:
listing all energy and material inputs into environment
evaluation of environmental impacts from inputs and outputs
interpreting results to help make decisions
why are results of an LCA always open for debate
when considering environmental impact, common to convert data to single score
requires subjective decisions-bias
sometimes no factual evidence so estimations made
what is the collision theory
states in order from chemical reaction to occur, particles must collide with sufficient energy
minimum energy required for particles for reaction to be successful is the activation energy
what happens as the reaction progresses
contraction of reactants decreases reducing frequency of collisions between particles so reaction slows down
how to increase the rate of a chemical reaction
particles must collide more frequently and/or collide with more energy
how to achieve a higher rate of reaction
increase concentration
increase temperature
increase pressure
