Identify the type of attraction represented by the dotted lines shown between the layers.

Graphite is used as a lubricant. Discuss two other uses of graphite with reference to its layered structure.

van der Waals’/vdW/London/dispersion (forces)/LDF / temporary/instantaneous/induced dipoles;

Two of the following pairs:

used as pencil (lead);

layers can flake off/slide off/break off/stick to paper / OWTTE;

M2 must contain concept of separation of layers, so do not award mark for phrases like "layers can slide over each other" on their own.

OR

used as carbon fibre / OWTTE;

bonding within layer is strong / layers are extensive / layers are strong;

OR

used as electrodes/conductor/in batteries;

has mobile/free/delocalized electrons (between layers) / electricity flows parallel to layers;

OR

used for thermal insulation;

vibrations are not easily passed between layers;

Accept other valid uses of graphite along with a suitable explanation.

Less than half the candidates recognized van der Waals’ forces between the layers in graphite. Some candidates identified the type of attraction as “electrostatic” and others as “intermolecular forces” which were too general and did not score the mark.

Well answered generally. Most candidates gave two uses (usually pencil lead and electrical conductor) and they were often able to explain the uses in terms of the structure.