EX.M9

IGCSE 0654 COORDINATED SCIENCE CHEMISTRY element A pure substance made of only one kind of atom compound A substance made up of atoms of two or more different elements joined by chemical bonds chemical formula A combination of chemical symbols and numbers to represent a substance chemical symbols shorthand way of writing the names of the elements subscript A number written slightly below and to the right of a chemical symbol that shows how many atoms of an element are in a compound. physical state symbols (s) (l) (g) (aq) Manufacture of lime (CaO) (Calcium oxide) 1000°C CaCO3 - CaO +CO2 Lime uses Cement Limelight (heated to 2400°C) here it glows. Slaked lime uses (Ca(OH)2) Raising soil PH Neutralizing acidic waste Sewage treatment Manufacture of slaked lime CaO + H2O - Ca(OH)2 Uses of calcium carbonate Making CaO Raising soils PH Sulfuric acid uses Oil refining Fertilizer production Paper and steel making Acid in car batteries H₂SO₄ diluted in water H₂SO₄ - 2H⁺ + SO₄²⁻ The contact process This is how sulfuric acid is produced Sulfur sources Underground bedrock Volcanic deposits Sulfur dioxide uses Bleach in the manufacture of wood pulp for paper Food preservative Sulfuric acid reacts with metals, alkalis, and carbonates. first step of contact process S + O₂ - SO₂ second step of contact process 2SO₂ + O₂ - 2SO₃ third step of contact process dissolve sulfur trioxide in concentrated sulfuric acid to form oleum (H₂S₂O₇) final step of contact process Add H₂O to form even more H₂SO₄ ratio of sulfur dioxide to oxygen used 1:1 temperature conditions 400-450°C pressure conditions 1-2 atmospheres Catalyst V₂O₅ Water, H2O (uses) cleaning, drinking, industry for cooling. drinking water (from where?) from rivers, lakes, aquifers. they have pollutants in them filtration (water) water passed fine filters to trap suspended particles. activated carbon used to filter out dissolved pollutants Chlorination chlorine is added to water which destroys bacteria gases in air 78% nitrogen, 21% oxygen (small amounts of other gases, carbon, argon...) Carbon dioxide produced by... burning carbon-containing fuels, thermal decomposition of carbonates, respiration in living cells global warming (impacts) greenhouse effect, increasing temperature and weather changes Air pollution carbon monoxide, Sulphur dioxide, nitrogen oxides carbon monoxide, CO forms when fuels burn with enough O2, prevents blood from carrying oxygen Sulphur dioxide, SO2 formed by burning fossil fuels containing Sulphur impurities, dissolves in water in clouds to make sulphurous acid to make acid rain