C9 Seperate chemistry 2 Flashcards
How small are nanoparticles?
1-100 nanometres
Nanoparticles have a very _____ SA:VOL
large
How do you figure out SA:VOL of cubic nanoparticle?
e.g. sidelength 20nm
- area of cube face
- area if 6 cube faces
- volume if cube
- SA:VOL ratio
- Divide by bolume so we can compare
e. g.
1. A=20x20 = 400nm^2
2. A=6x400 = 2400nm^2
3. V= 20x20x20 = 8000nm^3
4. 2400 : 8000
5. 0.3 : 1
What happens to SA:VOL ratio if we half the size if our nanoparticle?
SA:VOL ratio increases by factor of 2
Why do we add nanoparticles to sunscreen?
- absorb/block UV light from the skin which prevents sunburn
- very small so cannot be seen on skin
Why do nanoparticles make good catalysts?
- reactions occur on the surface if catalysts
- nanoparticles have a large SA:VOL ratio
- Larger SA means more successful collisions will occur
- Which increases RoR
- Large SA:VOL means only small quantity needed
What are the disadvantages of nanoparticles? (3 points)
- new technology
- thus we dont know the long term risks
- nanoparticles are so small they could pass into our cells/bloodstream
- so they could change the nature of chemical reactions in our body
- nanoparticles can be washed into the environment
- so they can end up in other organisms
- and build up in food chains causing problems
What are polymers?
- long chain carbon molecules
- made up of monomers
- held together by strong covalent bonds
What are examples of polymers?
- polyester
- LDPE
- HDPE
- polystyrene
- polypropene
- polytetrafluroethene(PTFR/Teflon)
- polychloroethene(polyvinyl chloride/PVC)
What are ceramics?
- non-metallic
- inorganic (non-carbon)
- solids
- made from metal/non-metal compunds that have been shaped and then hardened by heating to high tmeperatures
What are some examples of ceramics?
-clay ceramics
a mineral made from weathered and decomposed rock – soft and mouldable until heated
-glass
made from limestone, sand and sodium carbonate which is heated until it melts
What are composites?
- made from fibres of fragments of one material (the reinforcement)
- embedded into another material (matrix/binder)
What are examples of composites?
-fibreglass
glass embedded in polymer
-carbon fibres
long chains of carbon embedded in polymer
-concrete
sand and gravel embedded in cement
What are metals?
naturally occuring elements extracted from ores
What is tensile strength?
how easily something can break/shatter
low = easy to break/stretch/shatter high = hard to break/stretch/shatter
What ions does the flame test test for?
- lithium
- calcium
- sodium
- copper
- potassium
Why must the test for ions be unique?
- when electrons lose energy it will drop down to a lower energy level
- it will lose energy equal to the difference between two energy levels
- energy emitted in form of visible light unique to each element
therefore
the test must be an easy-to-observe result that is specific to the ion present
What ion is present if a red flame is produced?
Lithium