C10. Metals

Properties of metals Metals physical properties includes: they are; Ductile; they can be drawn into wire, Malleable; they can be hammered into sheets Have a high melting point they also have high density, good conductors of electricity and heat Metals chemical properties include; Reaction with water, most reactive metals (K-Ca) react with cold water, fairly reactive metals (Mg-Fe) will only react with steam whereas the least reactive metals (Sn-Pt) don’t react at all. Reaction with dilute acids, Most reactive metals (K-Ca) reacting violently, the fairly reactive metals (Mg-Pb) reacting gradually more slowly and the least reactive metals (Cu-Pt) not reacting at all. Displacement Reactions The reactivity of metals relates to how easily they form ions, more reactive metals like K form K+ ions much more easily than less reactive metals like Cu can form Cu+ ions. A more reactive metal will reduce a less reactive metal

Alloys Alloys are ‘mixtures of two or more metals’ (although sometimes they can contain a non-metal) that are made by mixing molten metals Alloys often have very different properties to the metals they are made from by varying their properties, metals can be tailored to have specific desirable properties – this is called metallurgy Alloys are often harder than the metals they are made from. In pure metals atoms are neatly lined up meaning they can slip past each easily when hit. In alloys there are atoms of different sizes which don’t line up neatly so can’t slip past each other so easily making them harder.

Some uses of Alloys Alloy Properties Uses Brass (Copper + Zinc) Stronger than copper but still malleable, gold coloured, shiny & does not corrode To make musical instruments, door knobs, locks & ornaments Bronze (Copper + Tin) Very hard To make moving parts of machines, bells, statues etc. Stainless Steel (Iron + Chromium+ Nickel) Does not rust like Iron To make cutlery, car parts, surgical instruments etc.

Increase in reactivity Reactivity series MOST REACTIVE Potassium, K Sodium, Na Calcium, Ca Magnesium, Mg Aluminium, Al (Carbon, C) Zinc, Zn Iron, Fe Tin, Sn Lead, Pb (Hydrogen, H) Copper, Cu Silver, Ag Gold, Au Platinum, Pt LEAST REACTIVE In a reactivity series, the most reactive element is placed at the top and the least reactive element at the bottom. More reactive metals have a greater tendency to lose electrons and form positive ions. metals above hydrogen reacts with dilute acids, to produce salt and hydrogen gas. metals below hydrogen will not react with dilute acids K, Na, Ca & Mg react with cold water forming an alkali solution and hydrogen gas Zn & Fe react with steam forming metal oxide and hydrogen gas The vigour of the reaction decreases down the reactivity series more reactive metals will reduce the less reactive metals i.e. will displace them from their compounds Increase in reactivity

Extraction of metals Rocks that contain a significant amount of a metal are called ores. Metals occur in ores as compounds – often oxides or sulphides of the metal. Examples; lead is extracted from an ore called galena (PbS, lead sulphide). Iron is extracted from an ore called Haematite (Fe2O3, Iron III oxide). Aluminium is extracted from an ore called bauxite (Al2O3, Aluminium oxide). The method of metal extraction depends on the position of the metal on the reactivity series metals above carbon on reactivity series e.g. Al, Mg & Ca are extracted by electrolysis. metals below carbon on reactivity series e.g. Zn, Fe & Pb are extracted by using carbon to reducing oxides of metals Example: PbO(s) + C(s) → Pb(s) + CO(g) Carbon monoxide is produced in the furnace and used for extraction of metal Example; 2C(s) + O2(g) → 2CO(g) ZnO(s) + CO(g) → Zn(s) + CO2(g)

Extraction of iron in the blast furnace Iron is less reactive than carbon so it extracted by using carbon to reduce it’s oxide, this is done in a blast furnace Step 1: Carbon (coke) reacts with oxygen (from the hot air blast) C(s) + O2(g) → CO2(g) Step 2: Carbon dioxide reacts with more carbon to make carbon monoxide CO2(g) + C(s) → 2CO(g) Step 3: Carbon monoxide reduces the iron oxide (iron ore) to make molten liquid iron. Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g) The limestone (CaCO3) reacts with impurities such as silicon to form an easy-to-collect waste called slag (calcium silicate, CaSiO3): CaCO3(s) +SiO2(l) → CaSiO3(l) + CO2(g) The liquid slag is run off at the bottom and it is used as a building material in road construction

Uses of metals Metals have many uses including: Aluminium– and its alloys used for aircraft as they have low density and great strength Aluminium– is used for food containers (drink cans, cooking foil & food cartons) as it is non-toxic, can be rolled into sheets and resistant to corrosion Aluminium– is used for overhead electricity cables since it is a good conductor of electricity, ductile & resists corrosion Zinc – is used to protect steel either by coating it (galvanising) or as sacrificial protection to protect it from rusting to galvanise steel, a steel object is dipped into liquid zinc for zinc to form a coating on the surface of steel in sacrificial protection, a lump of zinc is attached to the ship’s hull to prevent rusting as it is more reactive than steel so it corrodes instead of the steel hull