Distinguish between metals and non-metals on the basis of four physical properties. Name an exception for any two of them.

1. 1 · Open. Metals and non-metals differ in physical properties, which we can observe without changing the substance.
2. 2 · Four differences.
   • Lustre: metals shine; non-metals are dull
   • Malleability and ductility: metals have them; non-metals are brittle
   • Conduction: metals are good conductors; non-metals are poor
   • Sound: metals are sonorous; non-metals are not
3. 3 · Exceptions. Graphite, a non-metal, conducts electricity; iodine has lustre; mercury is a liquid metal; sodium is soft.
4. 4 · Real life. Copper wires and aluminium vessels make use of the conductivity of metals.
5. 5 · Close in one line. So most, but not all, elements can be sorted by these properties.

Scoring tip: Write each difference as a pair: metals versus non-metals. One-sided answers get half the marks.