Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Metals and their Compounds
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Metals and their Compounds
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Subject: Chemistry
Class: Senior Secondary 3
Term: 1st Term
Week: 3
Theme: Chemistry And Industry
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state the generalcharacteristics of metals; Identify what partsof the periodic tablecontain metals; state the relativeabundance of metals in nature; list five classes of compounds for med by metals (i.e. sulphates,chlorides etc); state the generalprinciples of extractionof metals; list the properties of alkali metals describe the extractionand give the uses of sodiumas a typical alkali metal list five compounds of sodium list the properties of alkaline earth metals describe the extractionand give the uses of calciumas a typical alkaline earthmetal describe the extractionof aluminum list five compounds of aluminum list five uses of aluminum describe the extractionof tin metal state five...
These are the elements with atomic numbers 21 to 30: Scandium (Sc) Titanium (Ti) Vanadium (V) Chromium (Cr) Manganese (Mn) Iron (Fe) Cobalt (Co) Nickel (Ni) Copper (Cu) Zinc (Zn) Transition elements exhibit unique properties due to their partially filled d-orbitals: Variable Oxidation States: They can show multiple positive oxidation states (e.g., Fe2+, Fe3+; Mn2+, Mn3+, Mn4+, Mn7+).
Formation of Coloured Compounds: Most transition metal ions and their compounds are coloured both in solid state and in solution (e.g., CuSO4 is blue, KMnO4 is purple, K2Cr2O7 is orange).
Formation of Complex Ions: They act as central metal ions and form complex compounds by accepting lone pairs of electrons from ligands (e.g., [Cu(NH3)4]2+).
Catalytic Activity: Many transition metals and their compounds act as catalysts in various chemical reactions (e.g., Fe in Haber process, Ni in hydrogenation of oils, V2O5 in Contact process).
Paramagnetism: Most transition metals and their compounds are paramagnetic (attracted to a magnetic field) due to the presence of unpaired electrons in their d-orbitals. Copper is mainly extracted from its sulphide ores like chalcopyrite (CuFeS2), bornite (Cu5FeS4), or chalcocite (Cu2S). Oxide ores are less common. Extraction from Sulphide Ore (e.g., Chalcopyrite, CuFeS2): This is a multi-step process: Concentration: The ore is crushed and concentrated using froth flotation to separate chalcopyrite from gangue.
Roasting: The concentrated ore is heated strongly in air to remove volatile impurities (e.g., arsenic, antimony) and convert some sulphide to oxide. `2CuFeS2(s) + O2(g) → Cu2S(s) + 2FeS(s) + SO2(g)` (simplified) Sulphur dioxide (SO2) produced is used to make sulphuric acid.
Smelting: The roasted ore is mixed with silica (SiO2) and heated in a reverberatory furnace at high temperatures (approx. 1400 °C). Iron sulphide (FeS) reacts with silica to form iron silicate slag (FeSiO3), which floats on top and is removed. The remaining molten mixture, primarily copper(I) sulphide (Cu2S) and some unreacted FeS, is called copper matte. `FeS(l) + SiO2(s) → FeSiO3(l) (slag)` Bessemerisation (Converting): The molten matte is transferred to a Bessemer converter, where air (sometimes enriched with oxygen) and silica are blown through it. Any remaining FeS is oxidised to FeO, which reacts with silica to form slag. `2FeS(l) + 3O2(g) → 2FeO(l) + 2SO2(g)` `FeO(l) + SiO2(s) → FeSiO3(l)` Copper(I) sulphide is then converted to molten copper metal, and SO2 gas is evolved. `2Cu2S(l) + 3O2(g) → 2Cu2O(l) + 2SO2(g)` `2Cu2O(l) + Cu2S(l) → 6Cu(l) + SO2(g)` The crude copper obtained at this stage is called blister copper (98% pure) because of the blisters formed by the escaping SO2 gas.
Refining (Electrolytic Refining): Blister copper is further purified by electrolysis to obtain very high-purity copper (99.9%).
Anode: Thick plates of impure blister copper.
Cathode: Thin sheets of pure copper.
Electrolyte: Acidified copper sulphate solution (CuSO4/H2SO4).
Process: During electrolysis, impure copper dissolves from the anode, and pure copper is deposited on the cathode. More reactive metals (e.g., Zn, Fe) also dissolve but remain in solution as ions. Less reactive metals (e.g., Ag, Au, Pt) fall to the bottom as anode sludge, which is a valuable by-product.
Anode: `Cu(s) → Cu2+(aq) + 2e−` (and other more reactive metals)
Cathode: `Cu2+(aq) + 2e− → Cu(s)` Electrical Wiring: Excellent electrical conductivity makes it ideal for household wiring, power transmission lines, and electronic components.
Plumbing and Roofing: Durable, corrosion-resistant, and easily fabricated for water pipes and roofing materials.
Alloys: Forms important alloys like: Brass: Copper + Zinc (for musical instruments, plumbing fixtures, decorative items).
Bronze: Copper + Tin (for sculptures, bells, historical artifacts, engine parts).
Coinage: Used in the production of coins due to its durability and resistance to corrosion.
Fungicides and Pesticides: Copper compounds (e.g., Bordeaux mixture, copper sulphate) are used in agriculture.
Infrastructure Development and Construction: Application: Metals like iron (as steel), aluminium, and copper are indispensable for Nigeria's infrastructure. Steel is used in bridges (e.g., the Lagos Third Mainland Bridge, Niger Bridge), high-rise buildings, roads (reinforcement bars), and railway tracks. Aluminium is critical for roofing sheets across the country, window frames, and structural components due to its lightweight and corrosion resistance. Copper is extensively used in electrical wiring for homes, offices, and industries, as well as in power transmission lines across the national grid.
Integration: Learners can be tasked to identify metallic components in their school buildings, homes, or local environment and discuss their specific properties that make them suitable for those applications. A field trip (or virtual tour) to a local construction site or manufacturing facility could highlight this. Industrial Processes and Economic Significance: Application: The extraction and processing of metals form a significant part of Nigeria's industrial sector and economy. Historically, tin mining in Jos contributed significantly, and iron ore extraction in Itakpe supports the Ajaokuta Steel Company (though currently underperforming). The manufacturing sector uses metals to produce vehicles, machinery parts, agricultural tools, and household items. The oil and gas industry relies heavily on steel and other alloys for pipelines, drilling rigs, and refinery components.
Integration: Discuss the economic impact of local metal industries, current challenges (e.g., power supply, raw material sourcing), and potential for growth. Students could research companies in Nigeria that use metals extensively (e.g., vehicle assembly plants, construction companies, cable manufacturers). Corrosion Management and Environmental Impact: Application: Corrosion (especially rusting of iron) is a major problem in Nigeria, causing significant economic losses through the deterioration of vehicles, bridges, pipelines, and other metal structures. Understanding corrosion and its prevention methods (e.g., galvanising, painting, cathodic protection for oil pipelines) is crucial for asset preservation and safety. The environmental impact of metal extraction (e.g., mining waste, SO2 emissions from copper smelting) and responsible disposal of metal waste are also important considerations.
Integration: Students can be asked to identify examples of corrosion in their communities (e.g., rusty gates, vehicles) and suggest appropriate prevention methods. Discuss the importance of recycling metals to reduce environmental impact and conserve resources, connecting it to Nigeria's efforts in waste management. ---