Fig. 1 shows a product made from a range of materials. It is made to last. The parts fit well. It is safe to use. The shape is good. It does its job well. A...

(a) A suitable metal for the body of a kitchen saucepan is stainless steel (or aluminium). [1] Stainless steel is a good thermal conductor, allowing heat to transfer efficiently from the hob to the food, and it is resistant to corrosion, so it does not rust or react with foods. [1]

(b) The metals most commonly used for each product:

• Product A (water pipe for plumbing): Copper. [1] Copper is malleable, corrosion-resistant, and does not contaminate the water supply.
• Product B (structural beam for construction): Mild steel. [1] Mild steel is strong, tough, and can be rolled into large structural sections.
• Product C (drinks can): Aluminium. [1] Aluminium is lightweight, corrosion-resistant, and easily recyclable.

(c) The process of annealing mild steel: The workpiece is heated to cherry red (approximately 720 degrees Celsius). [1] It is then allowed to cool very slowly, either by leaving it in the furnace with the heat turned off or by burying it in sand. [1] This relieves internal stresses and makes the metal softer and more ductile, easier to work further. [1]

(d) Suitable metals for each product:

(e) The steel used for the screwdriver blade is high carbon steel. [1] The blade must be heat treated because it needs to be hardened so it does not wear down when turning screws, and tempered to reduce brittleness so it does not snap under force. [1]

Hardening: heat the blade to cherry red and quench rapidly in water or oil. [1] Tempering: reheat to a lower temperature (around 230-300 degrees Celsius) and quench again, removing brittleness while retaining hardness.

(f) A suitable alloy for a lightweight bicycle frame is aluminium alloy (e.g. 6061 aluminium). [1] Chromoly (chromium-molybdenum steel alloy) and titanium alloy are also acceptable.

Two properties making it suitable:

1. Lightweight / low density, reducing the overall weight of the bicycle for easier pedalling and manoeuvrability. [1]
2. High strength-to-weight ratio, providing the structural rigidity needed to support the rider and withstand pedalling forces without being heavy. [1]

One advantage of using an alloy rather than a pure metal: Alloys combine properties of their constituent metals, giving a better combination of strength, hardness, and corrosion resistance than any single pure metal could provide on its own. [1] Pure aluminium, for example, is too soft for a bicycle frame, but when alloyed with small amounts of magnesium and silicon, it becomes significantly stronger while remaining lightweight.

(g) The metal for the cutting edge of a cold chisel is high carbon steel (tool steel). [1]

Case hardening process: The chisel is packed in a carbon-rich material (charcoal or carbon powder) in a sealed container and heated to around 900-950 degrees Celsius for several hours. [1] Carbon atoms absorb into the outer surface layer. The component is then quenched in water or oil to harden the carbon-enriched outer layer. [1] This creates a hard, wear-resistant cutting edge while the core remains tough enough to absorb hammer impacts without fracturing.

One disadvantage of case hardening: only the outer surface is hardened, so the hard layer can wear through with heavy use, exposing the softer core. [1]

The heat treatment process carried out after hardening to prevent brittleness is tempering. [1]

(h) The steel used for the bracket is mild steel. [1] Mild steel is strong and easy to bend and shape, making it suitable for forming into an L-shaped bracket, and it is inexpensive and tough enough to support a loaded shelf without snapping. [1]