Topic 1 Planet Earth Unit 1 Unit 2 Unit 3 Unit 4 Introducing chemistry The atmosphere The ocean Rocks and minerals
Key C o ncepts Planet Earth The atmosphere Classification of matter element, mixture and compound Separating oxygen and nitrogen from the air Physical and chemical properties of a substance Introducing chemistry Chemistry and our lives Laboratory safety rules and hazard warning labels Common apparatus in the laboratory The ocean Composition of sea water Obtaining common salt from sea water Obtaining pure water from sea water Showing what species common salt contains Useful materials obtained from sodium chloride The particle theory of matter Physical and chemical changes Rocks and minerals Metals in the Earth s crust Extracting metals from their ores Chemical reactions of calcium carbonate Formation of chalk, limestone and marble
Topic 1 Planet Earth Unit 1 Introducing chemistry Unit 1 Introducing chemistry 1.1 1.5 Summary 1.1 What is chemistry? 1.2 Why study chemistry? 1.3 Laboratory safety 1.4 Hazard warning labels 1.5 Common apparatus in the laboratory Hazard warning label Explosive Flammable Example(s) Ammonium dichromate Carbon monoxide Hydrogen Liquefied petroleum gas Town gas Ethanol Toxic Chlorine Carbon monoxide Mercury Carcinogenic Asbestos Suspected example: crude petroleum Concentrated nitric acid Oxidizing Corrosive Bromine Concentrated acids Concentrated aqueous ammonia Concentrated sodium hydroxide solution Harmful Iodine Irritant Dilute acids Dilute aqueous ammonia Exam tips Oxygen supports combustion, but it is NOT flammable. Chlorine bleach is usually a 5.25% sodium hypochlorite solution. A potential hazard of mixing an acidic toilet cleanser with chlorine bleach is that a toxic gas (chlorine) is liberated.
Topic 1 Planet Earth Unit 2 The atmosphere Example Explain why non-luminous flame is obtained when the air hole of a Bunsen burner is fully open. (2 marks) Unit 2 The atmosphere Answer Enough oxygen is provided when the air hole is fully open. (1) The fuel undergoes complete combustion. (1) Remarks* When using a Bunsen burner with the air hole closed, the fuel undergoes incomplete combustion. The burner gives a luminous flame. The yellow colour of the flame is due to the presence of tiny carbon particles. 2.1 The Earth 2.2 Classification of matter: pure substance and mixture 2.3 Elements and compounds 2.4 Differences between a mixture and a compound 2.5 The atmosphere 2.6 Separation of mixtures 2.7 Separating oxygen and nitrogen from the air 2.8 Physical and chemical properties 2.9 Test for oxygen
Topic 1 Planet Earth Unit 2 The atmosphere 2.1 2.9 Summary 1 Classification of matter: matter 8 Physical properties of a substance are properties that can be measured without changing the chemical composition of the substance. e.g. colour odour taste state pure substances can be separated by simple physical methods mixtures melting point boiling point 9 Chemical properties of a substance are properties that describe its ability to form new substances. elements (e.g. hydrogen, oxygen, iron, sulphur) can be separated by chemical methods compounds (e.g. water, iron(ii) sulphide) e.g. reaction with oxygen reaction with water 2 A pure substance is a single substance that has nothing else mixed with it. 3 A mixture is a substance composed of two or more pure substances which have not been chemically joined together. reaction with acids / alkalis 10 A simple test of oxygen is that it can relight a glowing splint. 4 Elements are substances which cannot be broken down into anything simpler by chemical methods. 5 Compounds are substances composed of two or more elements chemically joined together. 6 The approximate percentage composition of gases in the air (in percent by volume) is as follows: Gas in air Approximate percentage (by volume) Nitrogen 78% Oxygen 21% Other gases (including noble gases, carbon dioxide and water vapour) about 1% (noble gases 0.9% carbon dioxide 0.03 0.04% water vapour varying amount) 7 In industry, oxygen and nitrogen in the air are separated by fractional distillation of liquid air. Exam tips Example Students should be able to tell whether a substance is a single compound. e.g. Ethanol is a single compound. Petrol is a mixture of compounds. Vinegar is a mixture of ethanoic acid and water. Students should be able to give correct wordings. e.g. Oxygen relights a glowing splint, NOT a growing splint. 4 Work in a fume cupboard, NOT a flame cupboard. 4 The following table gives some information of certain components in a sample of liquid air: Component Boiling point ( C) Argon 186 Nitrogen 196 Oxygen 183
10 Topic 1 Planet Earth Unit 3 The ocean 11 a) Name ONE other gas found in dry air. (1 mark) b) An industrial method can be used to separate nitrogen and oxygen from the sample. i) Name the industrial method. (1 mark) ii) In what order would the components be distilled off when the sample undergoes the process? Explain your answer. (2 marks) Answer a) Carbon dioxide (1) b) i) Fractional distillation (1) ii) The order is: nitrogen, argon, oxygen. (1) Nitrogen has the lowest boiling point. Thus, it will be distilled off first. Oxygen has the highest boiling point. Thus, it will be distilled off last. (1) Remarks* Carbon dioxide is NOT obtained industrially from the fractional distillation of liquid air. Unit 3 The ocean 3.1 Sea water: a vast solution 3.2 Obtaining common salt from sea water 3.3 Obtaining pure water from sea water 3.4 Showing what species common salt contains 3.5 Test for the presence of water in a sample 3.6 Electrolysis of sea water 3.7 Uses of the products obtained by the electrolysis of sea water 3.8 The particle theory of matter 3.9 Physical and chemical changes
12 Topic 1 Planet Earth Unit 3 The ocean 13 3.1 3.9 Summary 1 Sea water contains 3.5% by mass of dissolved salts, including a) sodium chloride; b) magnesium chloride; c) sodium sulphate; and d) calcium chloride. 2 A solution forms when one substance dissolves in another. The substance that dissolves is called the solute. The substance that does the dissolving is called the solvent. solute + solvent = solution 3 A dilute solution contains a small amount of solute in a given volume of solution. A concentrated solution contains a large amount of solute in a given volume of solution. 4 A saturated solution is a solution that has dissolved the most solute it can, at a given temperature. 5 The following table summarizes some common separation methods: 11 The particle theory of matter states that all matter is made up of very small particles. 12 a) During a physical change, no new substance is formed. b) In a chemical change, one or more new substance(s) is / are formed. 13 The following words are used to describe the changes of states of a substance. solid deposition sublimation gas melting freezing boiling (or evaporation) condensation liquid Separating process Method(s) of separation Example Separating a much denser insoluble solid from a liquid Separating an insoluble solid from a liquid Separating a dissolved solid (solute) from a solution Separating solvent and solute from a solution decantation filtration evaporation or crystallization distillation separating coarse sand from sea water separating mud from muddy sea water obtaining common salt from sea water obtaining pure water and salt from sea water Exam tips Filtration CANNOT remove sodium chloride from sea water. To obtain salt from a salt solution, use evaporation or crystallization. To obtain both salt and water from a salt solution, use distillation. Consider a boiling tube containing hot saturated copper(ii) sulphate solution. Large crystals of the salt can be obtained by placing the tube on a bench for several days. Students should be able to describe the procedure for flame test. 6 The following table shows the flame colours of some metal compounds: Compound of Potassium Flame colour lilac nichrome wire solid sample Bunsen burner Sodium Calcium Copper golden yellow brick-red bluish green 7 To test for chlorides, first dissolve the sample in water, then add excess dilute nitric acid, followed by silver nitrate solution. Appearance of a white precipitate suggests that the sample is a chloride. 8 Common salt is sodium chloride. It is made up of two elements, sodium and chlorine. 9 A simple test for water is that it can turn blue cobalt(ii) chloride paper pink. 10 Useful substances can be obtained from sea water by electrolysis. sea water electricity chlorine gas + hydrogen gas + sodium hydroxide solution concentrated hydrochloric acid (a) Dip a clean nichrome wire into concentrated hydrochloric acid watch glass (b) Then dip the nichrome wire into the solid sample (c) Put the end of the wire in the Bunsen flame and observe the colour of the flame When describing a chemical test to show that water vapour is formed in a certain reaction, students may use anhydrous cobalt(ii) chloride paper or copper(ii) sulphate. When describing a test for water, state the colour change of the cobalt(ii) chloride paper. DO NOT just write down the colour of the paper after it meets water.
14 Topic 1 Planet Earth Unit 4 Rocks and minerals 15 Example Classify each of the following processes as either a physical or chemical change. Explain your answer. a) Fractional distillation of petroleum (1 mark) b) Rusting of iron (1 mark) c) Formation of dry ice from carbon dioxide gas (1 mark) d) Mixing sea water with silver nitrate solution (1 mark) e) Cracking of heavy oil (1 mark) Unit 4 Rocks and minerals 4.1 Metals in the Earth s crust 4.2 Extracting metals from their ores 4.3 Investigating calcium carbonate 4.4 Formation of chalk, limestone and marble 4.5 Formation of limestone caves Answer a) Physical change. No new substance is formed in the process. (1) b) Chemical change. New substance (rust) is formed in the process. (1) c) Physical change. No new substance is formed in the process. (1) d) Chemical change. New substance (a white precipitate / silver chloride) is formed in the process. (1) e) Chemical change. New substances (alkenes and alkanes) are formed in the process. (1) Remarks* Electrolysis of sea water is a chemical change.
16 Topic 1 Planet Earth Unit 4 Rocks and minerals 17 4.1 4.5 Summary 1 The individual chemical compounds that make up rocks are called minerals. Rocks from which we obtain metals are called ores. Exam tips Oyster shell contains mainly calcium carbonate. Limestone can be usesd as fire-proofing additive because the decomposition of calcium carbonate is an endothermic process. 2 Getting a metal from its ore is called extracting the metal. 3 The following table summarizes common methods for extracting metals from their ores: Physical method Heating the ore alone Extraction method Heating the ore with carbon Electrolysis of the molten ore panning for gold Example(s) extracting mercury from cinnabar extracting silver from silver oxide extracting iron from haematite extracting aluminium from its molten ore 4 The following table summarizes the action of heat, dilute acid and water on calcium carbonate: Action of Heat Dilute acid Water calcium carbonate heat CaCO 3(s) calcium oxide + water CaO(s) + H 2O(l) CaO(s) + CO 2(g) Change(s) calcium oxide (quicklime) + carbon dioxide Ca(OH) 2(s) calcium hydroxide (slaked lime) calcium carbonate + dilute hydrochloric acid calcium chloride + water + carbon dioxide CaCO 3(s) + 2HCl(aq) CaCl 2(aq) + H 2O(l) + CO 2(g) insoluble in water but soluble in dilute hydrochloric acid 5 Slaked lime is slightly soluble in water. The saturated solution formed is called limewater. 6 Limewater can be used to test for carbon dioxide gas. Carbon dioxide turns limewater milky due to the formation of insoluble white calcium carbonate. CO 2 (g) + Ca(OH) 2 (aq) CaCO 3 (s) + H 2 O(l) When an excess of carbon dioxide is passed into the limewater, the white precipitate disappears. This is because the precipitate dissolves to form soluble calcium hydrogencarbonate. Example An anhydrous compound X gives a brick-red flame in flame test. Upon strong heating, compound X gives off a gaseous product Y which turns blue cobalt(ii) chloride paper pink and a gaseous product Z which turns limewater milky. a) i) Identify gaseous products Y and Z (2 marks) ii) Write a chemical equation for the reaction between the gaseous product Z and limewater. (1 mark) b) What can be deduced about compound X from the observation in flame test? (1 mark) c) Suggest what compound X may be. (1 mark) d) In another experiment, the gaseous product Z is passed into sodium hydroxide solution instead of limewater. Explain whether a similar observation would be made. (1 mark) Answer a) i) Y is water vapour. (1) Z is carbon dioxide. (1) ii) Ca(OH) 2 (aq) + CO 2 (g) CaCO 3 (s) + H 2 O(l) (1) b) Compound X contains calcium. (1) c) Calcium hydrogencarbonate (1) d) No. Sodium carbonate is soluble in water. (1) Remarks* The following substances can be used to distinguish between oxygen and carbon dioxide: limewater; burning splint; glowing splint. CaCO 3 (s) + CO 2 (g) + H 2 O(l) Ca(HCO 3 ) 2 (aq) 7 Calcium carbonate occurs naturally in three main forms chalk, limestone and marble. 8 Solid rock can be broken down into smaller pieces and changed into other materials as a result of weathering. The wearing away of surface materials and the movement of products of weathering from where they formed to a different location is called erosion. The major causes of erosion are gravity, running water, waves, ice and wind.