DT - MATERIALS

• Metals are materials that are typically hard, shiny, and good conductors of heat and electricity.
• Metallic minerals are found naturally in rock or ore
• Ore is obtained by mining and the metals within it are extracted
• The method used for extraction depends on the metal’s reactivity with air, water or acids
• The more reactive the metal, the more expensive it is to extract
• Gold is expensive compared to aluminium because it is less reactive
• Metals such as copper, iron and zinc are oxides
• Metals such as copper, iron and zinc are heated with carbon to extract the metal
• Electrolysis is used to extract metals such as aluminium
• Iron can be extracted from iron ore by using a blast furnace and the process of smelting
• The extreme heat draws off the metals in a liquid state called ‘hot metal’
• The impurities are removed and the iron mixed or ‘alloyed’ with a small amount of carbon to create steel
• Ferrous metals contain iron and may rust
• Rust is a compound called iron oxide and is formed when iron and oxygen react in the presence of moisture or water
• Protective layers that could be added to metal to help prevent rust are
• Ductile metals will stretch without being damaged and can be drawn into long wires
• Malleable metals can be hammered into a shape without breaking and can be rolled or pressed into sheets
• Hardness is a material’s ability to withstand abrasion
• Toughness is how well a metal can absorb energy and resist fracturing without deforming
• Tensile strength is the amount of tensile stress a material can withstand before breaking
• High speed steel is formed by alloying elements of carbon, tungsten, vanadium, cobalt, chromium or molybdenum
• Everyday applications of stainless steel are
• Low carbon steel is tough, ductile and easily welded
• High carbon steel is very hard wearing, but less ductile or malleable
• Non-ferrous metals are more expensive than ferrous metals and are lightweight, good conductors, ductile, malleable, and resistant to corrosion
• Conductivity is how easily an electrical current can flow through a metal
• Thermal conductivity measures the ability of a metal to conduct heat
• Aluminium, copper, tin, and zinc are non-ferrous metals
• Alloys are made by combining two or more elements to improve working properties and appearance
• Stainless steel is made by combining iron with a small amount of carbon and chromium to prevent rusting
• Creating alloys helps prevent rust and improves the properties of the metal
• Non-ferrous metals such as copper and bronze may oxidise over time
• A thin layer of tarnish that appears on the surface of the metal is known as a patina
• A natural patina occurring on copper is called Verdigris
• Metals are commonly extracted from ores
• Three ferrous metals are
• Copper is selected for high conductivity
• An alloy is a combination of two or more elements
• Hardness refers to a material's ability to withstand abrasion, while toughness is a metal's ability to absorb energy without deforming
• Metal can be protected from oxidisation by adding a protective coat of zinc