- Transition metals: high melting point, dense, form coloured compounds, good catalysts e.g. iron
- Corrosion: metals get oxidised.
- To prevent rusting of iron:
- Exclusion of oxygen and water: use paint, oil/ grease, plastic
- Sacrificial protection: galvanise using a more reactive metal, which will rust first and prevent water and oxygen reaching the metal underneath
- Exclusion of oxygen: keep in vacuum container
- Exclusion of water: use a desiccant in the container (absorbs water vapour)
- Electroplating: the surface of a metal is coated with a less reactive metal
- Anode (positive): coating metal
- Cathode (negative): original metal
- Electrolyte: salt of the coating metal (as an aqueous solution)
- Uses: prevents corrosion, nicer looking e.g. tin cans covering steel
- Alloys: a mixture of two or more metals.
- Alloys are harder than pure metals because they contain different sized particles so they don't slide easily when hammered.
- Brass: 70% copper, 30% zinc.
- Steel: 96% iron, with carbon, phosphorus, silicon and sulfur impurities.
- Alluminium alloys with copper, manganese, sillicon: aircrafts as they light and strong e.g. magnalium.
- Bronze: copper and tin
- Gold alloys: less than 24 carat, the rest is copper or silver.
- Chemical cell: produces a voltage until one of the reactants is used up
- Hydrogen–oxygen fuel cell: hydrogen and oxygen are used to produce a voltage and water is the only product.
- 2H2(g) + O2(g) → 2H2O(l)
- 😄: no pollution, only waste is water, is rechargeable forever unlike batteries, quiet, efficient, continuous (will keep producing energy as long as fuel is supplied)
- 😦: expensive, difficult and expensive to store and transport hydrogen, dangerous? (too quiet)