Properties of ionic compounds and why?
Can conduct ONLY when molten or in solution - when solid, strong structure means ions are fixed in position and can’t move. In liquid, ions can move around and carry charge and energy
Soluble (mostly) - water molecules separate ions from the lattice
High melting and boiling points - high levels of energy needed to overcome electrostatic forces of attraction
Properties of simple covalent molecules and why?
Low melting and boiling points (often liquid or gas at room temperature) - weak intermolecular forces don’t need much energy to be overcome
Do NOT conduct electricity - they carry no overall CHARGE
Properties of giant covalent structures and why?
Very hard - they have rigid structures of strong covalent bonds
High melting and boiling points - “ “
Describe the structure of diamond?
Each carbon atom has covalent bonds to four other carbon atoms
Describe the structure, bonding and properties of graphite
Each carbon atom has covalent bonds to three others, forming layers, which slide over one another because there are no covalent bonds between layers. This makes it soft and slippery.
One electron from each carbon atom is delocalised - conduct heat and electricity
Define fullerene and give 3 examples of possible shapes
Carbon atoms bonded in hexagonal rings forming cage-like structures. Balls, onions, tubes
Possible usage of fullerenes?
Drug administration to specific parts of a body
Catalysts and lubricants
Properties of metals and why?
Malleable (can be shaped and bent), ductile (can be pulled into wires) - atoms are arranged in layers that can slide over one another
Why are alloys harder than pure metals?
Different sized ions in a metal disrupt the layers (imagine lots of small marbles and compare to that with a few big ones)
What are shape memory alloys?
Alloys that ‘remember’ their original shape and return to it on heating e.g. Nitinol used in dental braces
On what do the properties of a polymer depend?
The monomers used to make it
The conditions to carry out the reaction
Define thermosetting and thermosoftening polymers?
Thermosetting - they have strong covalent bonds across polymer chains so they don’t soften with heat
Thermosoftening - they soften with heat and reset when cooled because they have individual tangled polymer chains forming a web i.e. the intermolecular forces are broken and are brought back together
1 nanometre is how many metres?
1x10^-9 (0.000000001m or a billionth of a metre)
The study of small particles that are between 1 and 100 nanometres in size
What about them makes nanoparticles useful?
They have a high surface area to volume ratio so they are extremely reactive
What makes low density (LD) poly(ethene) different from high density (LD) poly(ethene)?
They are produced using different catalysts and reaction conditions
Possible uses of nanoparticles?
Computers, catalysts, coatings, sensors, strong and light construction materials, cosmetics