5.5 explain the uses of aluminium and iron, in terms of their properties.

Uses of aluminium and iron

Aluminium :

• aeroplane bodies: high strength-to-weight ratio
• overhead power cables: good conductor of electricity
• saucepans: good conductor of heat
• food cans: non-toxic
• window frames: resists corrosion

Iron

• car bodies: strong
• iron nails: strong
• ships, girders and bridges: strong

2.36 understand the sacrificial protection of iron in terms of the reactivity series.

Sacrificial protection of iron

Iron can be prevented from rusting by what we know about the reactivity series. Zinc is above iron in the reactivity series, so reacts more readily than iron.

So the iron is coated with zinc to stop rusting. 

2.35 describe how the rusting of iron may be prevented by grease, oil, paint, plastic and galvanising

Preventing rusting

Coating iron with:

• grease
• oil
• paint 
• plastic
• a metal less reactive than iron, such as tin

2.34 describe the conditions under which iron rusts

Rusting of iron

Rusting is a chemical reaction between iron, water and oxygen. Rusting takes place faster if there are also electrolytes such as sodium chloride in the water. NaCl is present in sea water.

Iron atoms have been oxidised as they have lost 3 electrons.