C2.3 - p1 Flashcards
what is an allotrope?
- different forms of an element in the same state
- but with different atomic arrangements
(ie. diamond, graphite)
state uses of graphene
- solar panels
- batteries
- increases a material’s strength without adding much weight (composite materials)
what are fullerenes?
structures that have hollow shapes
describe the shape of fullerenes
- shaped as tubes/balls
what can spherical fullerenes be used for?
- catalysts?
- lubricants - molecules acting like tiny ball bearings
- perhaps one day - drugs into body (can pass through cell membranes)
what happens when chemical bonds form? - energy
stored chemical energy is transferred to the surroundings
what are the bonds in simple molecules?
covalent forces between atoms, intermolecular forces between molecules
give examples of ionic compounds
sodium chloride
give examples of giant covalent structures
silica, diamond
give examples of simple molecules
oxygen, water,
what forces break when simple molecules boil/melt
the weak forces between the molecules, not the strong covalent bonds between each atom
(H20-H20) becomes H20 H20
what is the word used to describe substances that go directly from a solid to a gas?
sublimation
what is the word used to describe substances that go directly from a gas to a solid?
deposition
what determines whether a substance is brittle or malleable? (particles)
how easily the particles in the substance can change their positions in the lattice structure
why are metals malleable?
attracting force between electrons and metal ions remain, layers of ions only slide over each other
are giant covalent structure brittle?
yes
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are ionic compounds brittle, and if so why?
yes
- when a force is applied, ions slide over each other
- but they end up being like charges, and so they repel (pushing either side apart, and therefore breaking)
what allows a substance to conduct electricity?
whether or not it has delocalised electrons that can move
why do metals conduct electricity?
it has delocalised electrons that are free to move through the lattice
when do ionic compounds conduct electricity, and why?
- when molten/in the liquid state/ dissolved in water
- ions are then free to move
what are the size of coarse particles?
2,500 to 10,000nm long
disadvantages of using nanoparticles?
- so small can be breathed in/absorbed
- may take a long time to break down once released into the environment, and toxic substances may stick to surfaces
- risks difficult to predict (not much information known) — may be harmful to health + environment
what are properties of nanoparticles because of a large surface area to volume ratio?
- efficient (less quantity used to make product)
