Module 9 Chemicals from the earth

Metals

• recall some everyday uses of iron/steel, aluminium and copper (9.01)
• recall that most metals are extracted from their ores which are found in their natural state in the Earth
• understand that reduction is the loss of oxygen from a compound, eg the formation of copper from copper oxide
• define oxidation in terms of loss of electrons and reduction in terms of gain of electrons
• understand that the extraction of metals involves reduction of their ores relate the order of reactivities of metals to the stabilities of their ores and to their method of extraction

– by heating the ore with carbon monoxide (eg iron)

– by using electrical energy (eg aluminium)

• describe the process by which iron is extracted from iron oxide in a blast furnace, including outline diagrams, raw materials, reactions and the formation and uses of slag
• recall that a chemical reaction caused by electricity is called electrolysis
• understand that electrolysis is the movement of charged ions to the anode and cathode, followed by discharge
• describe the extraction of aluminium from purified bauxite including simple cell diagrams, nature of electrolyte and electrodes and reactions
• describe the purification of copper by electrolysis, including a simple diagram of the cell

The Transition metals

o locate the position of the transition metals in the periodic table

o describe the physical properties of the common transition metals (high melting points, good

o conductors of heat and electricity and high density as exemplified by iron and copper)

o recognise that transition metals form coloured compounds

o describe some uses of transition metals and their compounds as catalysts

The Alkali metals

o recall that lithium, sodium and potassium are alkali metals

o recall that the alkali metals have comparatively low melting points and are soft

o describe the reactions of lithium, sodium and potassium with water to form hydroxides which are alkaline (pH>7), and hydrogen gas

o describe the pattern in reactivity of the alkali metals lithium, sodium, and potassium towards water, and use this pattern to predict the reactivity of other alkali metals

Rocks and their uses.

• recall that hydrogen, chlorine and sodium hydroxide are produced by the electrolysis of concentrated aqueous sodium chloride (rock salt)
• recall the uses of sodium chloride, hydrogen and sodium hydroxide
• understand that the crystalline nature of igneous rocks and the fact that they do not contain fossils are evidence for their formation from hot, molten magma
• understand that crystal size in igneous rocks depends on the rate of cooling
• understand that the presence of fossils in a rock is evidence that it has been formed from sediments
• understand that in sedimentary rocks the deepest layers are usually the oldest, that sedimentary rocks may contain fossils, and that the type of fossil can help to date the rocks
• explain how metamorphic rocks are formed by the action of heat and pressure on existing rocks
• understand that metamorphic rocks having the same composition as other rocks is evidence for their formation from these rocks – for example marble and limestone are both calcium carbonate

The atmosphere

• recall the current composition of the atmosphere
• understand that the early atmosphere was probably formed from the gases produced by volcanic activity
• recall that originally the atmosphere probably contained a large amount of carbon dioxide together with water vapour, hydrogen, nitrogen and carbon monoxide
• explain the origins of the oceans by condensation of water vapour and describe how the percentage of carbon dioxide in the atmosphere was consequently reduced
• explain that the first primitive plants released oxygen as a result of photosynthesis and that the percentage of oxygen gradually increased
• explain that at present the atmosphere is in a state of approximate balance because

– the process of photosynthesis produces oxygen in the presence of sunlight

– respiration and the burning of fuels use oxygen and produce carbon dioxide

– carbon dioxide is absorbed by the seas and oceans

Useful products from the air

• recall the conditions under which nitrogen, from air, and hydrogen can be combined to form ammonia and that the Haber process is an important industrial process
• understand that this reaction is reversible and may reach a dynamic equilibrium
• explain the choice of conditions used in the Haber process in terms of rates of reaction and of the effects on equilibrium and yields of catalyst, pressure and temperature
• recall that nitrogenous fertilisers promote growth in plants
• understand that a nitrogenous fertiliser is manufactured by neutralising ammonia with nitric or sulphuric acid
• describe the environmental consequences of the over-use of fertilisers

The noble gases

• describe the noble gases as chemically inert compared with the other elements
• relate this lack of reactivity to the electronic arrangement in their atoms
• describe some uses of the noble gases in, for example, fluorescent lights, airships, balloons and light bulbs