Describe the properties of a solid.
- fixed arrangement of particles
- regular arrangement of particles
- particles cannot move, only vibrate in place
- particles cannot be compressed
- particles touch
Describe the properties of a liquid.
- medium intermolecular forces of attraction
- no fixed arrangement
- no regular arrangement
- particles touch
- particles cannot be compressed
- particles can slide over each other to move
- particles move to fill a container
Describe the properties of a gas.
- weakest forces of attraction
- no fixed arrangement of particles
- no regular arrangement of particles
- particles do not touch
- particles CAN be compressed
- particles move to fill a container
- particles move rapidly and randomly
What are the limitations of the particle model ?
- assumes particles are made of solid spheres
- assumes there are no forces operating in between particles
- the size of certain particles varies drastically based on what that particle actually is (ion, atom of which element etc.)
Describe the energy transfers that occur when a solid is heated to a temperature above its boiling point.
-
What effect does temperature and pressure have on a fixed mass of gas ?
- increasing temp of a gas increases gas particles’ energy
- particles move more rapidly and with more force
- pressure increases
What is it called when a gas turns straight into a solid ?
deposition
What is it called when a solid turns straight into a gas ?
sublimation
Which force of attraction is referred to when talking about ions (including giant ionic lattices/structures) ?
ELECTROSTATIC force of attraction
Explain why solid ionic compounds cannot conduct electricity.
- very strong electrostatic forces hold lattice together
- ions cannot move to carry charge
- can only carry charge when molten (high temp gives enough energy to break forces) or in solution (water molecules separate ions from lattice) as forces are then broken and ions can move to carry charge
What is a single, double, triple and so on covalent bond ?
- single = one pair of shared electrons involved
- double = two pairs of shared electrons involved
- triple = three pairs of shared electrons involved
etc.
Why do simple molecules have low melting and boiling points ?
weak INTERMOLECULAR FORCES - less energy to break
Why don’t simple molecules conduct charge ?
- no overall charge on account of covalent bonds
- don’t conduct electricity
What is the relationship between intermolecular force strength and size of a molecule ?
bigger size = stronger force
What are the limitations of the 2D ball and stick model ?
show bonds at 90’ but are at different angles
What are the limitations of the 3D ball and stick model (on paper) ?
hard to visualise 3D shape
What are the limitations of the dot and cross model ?
- in reality, all electrons are identical
- electrons are constantly moving in reality
- electrons are usually between the nuclei of the bonded atoms in reality
What type of force is referred to when discussing giant covalent structures ?
COVALENT BONDS
Name three properties of a giant covalent structure (in general).
- insoluble in water
- hard (doesn’t apply to graphite)
- don’t conduct electricity (doesn’t apply to graphite)
- high mps and bps
Describe the structure of graphite.
- arranged in layers of atoms
- only 3 covalent bonds between atoms
- each atom has one free electron in between the hexagonal graphite layers which can move to carry charge
- weak intermolecular forces between layers so are easy to slide, making graphite soft
What are some properties of fullerenes and how are these taken advantage of ?
- high tensile strength (so used to reinforce composites)
- high electrical and thermal conductivity due to the bonding replicating graphite’s and so having delocalised electrons (so used in the electronics industry)
- many have cage-like structures (can be used for medicine/drug/radiation delivery in medical treatments)
- large SA:V ratio of nanoparticles (used as lubricants)
Name 4 properties of graphene.
- extremely low density
- most reactive form of carbon
- even better thermal and electrical conductor than graphite
- strong for its mass
Give one future application of graphene.
quicker, more powerful computer chips
Describe the structure of metals.
- layers of regularly arranged POSITIVE IONS
- ‘sea’ of delocalised electrons surrounding the ions, so can carry charge throughout the metallic lattice
- lattice held together by ELECTROSTATIC FORCE OF ATTRACTION between POSITIVELY CHARGED IONS and NEGATIVELY CHARGED ELECTRONS IN THE SURROUNDING ‘SEA’
