AQA GCSE Chemistry 4.10.3 Using Materials Exam Questions

About AQA GCSE Chemistry 4.10.3 Using Materials

AQA GCSE Chemistry 4.10.3 is separate Chemistry only content about choosing and protecting materials. You learn what causes corrosion and how rusting is prevented by barriers and sacrificial protection, why alloys are used, and the composition and properties of bronze, brass, gold alloys, steels and aluminium alloys. You also compare glass, clay ceramics, polymers and composites. It is assessed on Paper 2 and builds on metallic bonding and alloys from 4.2.2, the reactivity series in 4.4.1 and polymers in 4.7. Examiners often ask you to explain sacrificial protection and to choose a material for a given use using data.

What you need to know

• Corrosion and rusting Corrosion is the destruction of materials by chemical reactions with substances in the environment. Rusting of iron needs both air (oxygen) and water.
• Preventing corrosion Barriers such as greasing, painting and electroplating stop air and water reaching the metal. Sacrificial protection uses a more reactive metal, such as zinc in galvanising, which corrodes instead of iron. Aluminium has an oxide layer that protects it from further corrosion.
• Alloys Bronze is copper and tin; brass is copper and zinc. Gold used for jewellery is usually an alloy with silver, copper and zinc; 24 carat is 100% gold and 18 carat is 75% gold. Aluminium alloys have low density.
• Steels Steels are alloys of iron with specific amounts of carbon and other metals. High carbon steel is strong but brittle; low carbon steel is softer and easily shaped; stainless steels contain chromium and nickel and are hard and resistant to corrosion.
• Glass and ceramics Soda-lime glass is made by heating sand, sodium carbonate and limestone. Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures. Clay ceramics such as pottery and bricks are made by shaping wet clay and heating in a furnace.
• Polymers and composites Properties depend on monomers and conditions: low density and high density poly(ethene) are made from ethene using different catalysts and conditions. Thermosoftening polymers melt on heating; thermosetting polymers do not, because of cross-links. Composites have a reinforcement (fibres or fragments) in a matrix or binder, for example fibreglass and concrete.

Common mistakes in 4.10.3 Using Materials

• Saying iron rusts in air alone or water alone. Both oxygen and water are needed.
• Saying zinc protects iron only as a barrier. In sacrificial protection zinc is more reactive, so it is oxidised instead of iron, even if the coating is scratched.
• Describing thermosoftening polymers as having cross-links. Thermosetting polymers have cross-links; thermosoftening polymers have only intermolecular forces between chains.
• Calculating carats wrongly: 18 carat gold is 18/24 = 75% gold.
• Confusing the matrix and the reinforcement in a composite.

Try three 4.10.3 Using Materials exam-style questions