C2 Flashcards
what is tensile strength?
the force needed to break a material when it is being stretched
what is compressive strength?
the force needed to crush a material when it is being squeezed
when can outliers be discarded?
if an error occured in the measurement
why have synthetic materials replaced many natural materials?
.some natural materials are in short supply
.they can be designed to give particular properties
.they are often cheaper and can be made in the quantity needed
what is crude oil made up of?
.hydrocarbons
.with chain molecules up to 100carbon atoms long
explain the stages of fractional distillation?
.the oil is heated up which turns it all into gas
.the distillation tower gets cooler when higher
.gas molecules condense into liquids when cool
.liquids with similar boiling points collect together called fractions
where attractive forces exist?
between molecules in crude oil, holding them together
what is a polymer?
large molecule made by joining many smaller molecules called monomers
what is the process in which a polymer is made?
polymerisation
what does PET stand for and what does it make?
.polyethylene terephthalate
.used to make drinking bottles
how can polymer chains be altered?
by replacing hydrogen atoms with other atoms or groups of atoms
describe low density polythene?
.long molecules with branches
.molecules are weak
.examples include plastic carrier bags
describe high density polythene?
.long chains .no branches .molecules are closer .long lasting .used to make water pipes
what are the characteristics of high crystalline polymers?
.strong
.high melting points
.can be brittle (bad)
what are plasticisers used for?
.making polymers softer
.inserted into polymer chains
.weakens forces
what soften when heated and can be moulded into shape?
thermoplastics
what plastics do not soften when heated, and contain cross links so don’t melt?
thermosetting plastics
how can crystallinity increased?
.removing branches
.making chains flat as possible
.line them up neatly
what process allows molecule chains to line up?
drawing polymers through a tiny hole when heated which increases crystallinity and forms a higher tensile strength fiber
what do nanopartcles contain?
up to a thousand atoms
where do nanopartcles occur?
.salt in sea Spray
.occur by accident
.can be designed in laboratories
what is nanotechnology?
is the use and controlled of very small structures
what is the scale of a nanometer?
a nanometer is one millionth of a millimeter
what are nanometer partials effective catalysts?
they have a large surface area which provides more sites for chemical reactions to take place on
what are sliver nanoparticals good at?
.killing bacteria
.can be used in socks, wound dressings, plastic
what nanoparticals are used in sun screen?
titanium oxide nanoparticals which make it transparent
what composite materials are made stronger by using nanoparticals?
.plastic sports equipment
.tennis balls
.rubber tyeres
what composite materials are made stronger by using nanoparticals?
.plastic sports equipment
.tennis balls
.rubber tyeres
what can graphene sheets be rolled into?
carbon nanotubes which are superstrenghth materials
what damage can be done by silver nanopartcles?
.washed out of cloths into sewers
.in sewage bacteria can clean the water and the nanoparticals can kill the useful bacteria
.if realised into the environment it could kill microorganisms
where do nanoparticals contain naturally?
.soot
.volcanic dust
define risk?
as the change of an event occurring and yh3 consequences of it
