C4 - Material Choices Flashcards
What are 3 substances covalent bonds can make?
- Polymers
- Giant covalent structures
- simple molecular structures
are covalent or intermolecular forces stronger?
covalent bonds are much stronger
what is a polymer?
is a large molecule, made up of lots of smaller units called monimers
what is a giant covalent structure?
a structure in which all atoms are bonded to each other by strong covalent bonds
name 3 examples of giant covalent structures?
diamond, graphite, and silicon dioxide
describe the bonding in simple molecular substances?
strong covalent bonds between atoms of each molecule, but weak intermolecular forces between the different molecules
what is an allotrope?
different physical forms of the same element in the same physical state
describe the structure and bonding of diamond
giant covalent lattice structure
each carbon is covalently bonded to 4 other carbon atoms, forming a repeating lattice
what are the properties of diamond?
- high melting and boiling points
- hard
- doesn’t conduct electricity
describe the structure and bonding of graphite?
- each carbon atom only forms 3 covalent bonds, creating sheets of carbon atoms, which are free to slide over each other
also has delocalised - electrons that can flow through the structure
what are the properties of graphite?
- high melting and boiling points
- soft and brittle
- good conductor of heat and electricity
why can graphite be used as a lubricant?
- carbon atoms are arranged in layers
- forces between layers are weak intermolecular forces
this means they don’t need as much energy to break, so they can slide over eachother
name 4 allotropes of solid carbon
diamond
graphite
graphene
fullerenes
what is graphene?
a single layer of graphite
give 4 properties of graphene
high melting and boiling points
strong
conducts electricity
very light
what are fullerenes?
are made of carbon atoms that exist as hollow shapes. such as spheres or cyclinders
what is a nanotube?
a tiny cylinder made of carbon atoms
why are nanotubes useful?
- high length to diameter ratio
- large surface area
- high tensile strength
- conduct electricity and heat
what is a ceramic?
group of non-metal solids with high melting points that aren’t made up from carbon based compounds
what is a composite material?
made of one material (reinforcer) embedded in another (matrix)
what are nano-particles?
small particles with a diameter of between 1 and 100nm
what is nanoscience?
field of research that focuses on nanoparticles. it looks at the properties and applications of nano particles
why do nanoparticles make good catalysts?
they have a high surface area to volume ratio, so only a small amount of material will be needed to have a large effect
what are the 4 stages of life cycle assesments?
- gathering the raw materials
- manufacturing and packaging
- using the product
- disposing the product
what are 2 disadvantages of life cycle assesments?
LCAs can be deliberately biased to support a country
what are finite resources?
resources which are not formed quickly enough to be considered replaceable
how can metals be recycled?
- melt the metals
- cast them into new shape
- use them to form new product
give 2 benefits of recycling
- we don’t have to use up so many new resources
- the waste products don’t fill up landfill sites
outline the process of recycling glass
some glass can be reused without processing
other glass has to be separated by colour and type, crushed, melted, and reshaped into a new product
what is the difference between low density poly ethene and high density poly ethene?
LDP:
catalyst
flexible but weaker
HDP:
rigid and stronger
catalyst
what is the difference between thermosoftening and thermosetting polymers?
thermosoftening polymers melt when they are heated, and can be remoulded
thermosetting polymers do not melt when they are heated, so cannot be remoulded
