Form 4 CHAPTER 1 Introduction to Chemistry...................... 1 CHAPTER 2 Matter and the Atomic Structure........... 6 CHAPTER 3 The Mole Concept, Chemical Formula and Equation ........................ 15 CHAPTER 4 The Periodic Table of Elements.......... 22 CHAPTER 5 Chemical Bond ................................... 39 CHAPTER 6 Acid, Base and Salt ............................ 49 CHAPTER 7 Rate of Reaction................................. 77 CHAPTER 8 Manufactured Substances in Industry............................................... 84 Form 5 CHAPTER 1 Redox Equilibrium .............................. 92 CHAPTER 2 Carbon Compound ........................... 137 CHAPTER 3 Thermochemistry.............................. 155 CHAPTER 4 Polymer ............................................ 170 CHAPTER 5 Consumer and Industrial Chemistry ......................................... 183 ii CONTENTS
CHAPTER 1 INTRODUCTION TO CHEMISTRY 1.1 Development in Chemistry Field and Its Importance in Daily Life Theme: 1 • Chemistry is a field of science that studies the structures, properties, compositions and interactions between matter. Chemicals in daily life Field Chemicals Uses Food Flavouring Enhance the taste of food. Sweetener To make food and drink sweeter. Preservative To slow down or prevent the growth of microorganisms. Medicine Analgesics Applied to the surface of skin or wound to prevent infection. Antimicrobials Used to kill or retard the growth of microorganisms. Agriculture Fertiliser To enhance plant growth. Pesticide Poison to kill pests, such as insects, rodents and etc. Industry Paint To protect the exterior of a building. Glass Making laboratory apparatus and tableware. 1
Development of the atomic structure model Dalton’s atomic model − Matter is made up of particles i.e., atoms. Thomson’s atomic model − Discover negativelycharged particles i.e., electrons. Chadwick's atomic model − Discover neutron in the nucleus. Rutherford 's atomic model − Discover nucleus as the centre of the atom and positively-charged particles i.e.,proton Bohr’s atomic model − Electrons move around the nucleus in its shell. Negatively–charged electron Positively–charged sphere Electron moves outside the nucleus Nucleus that contains protons Shell Electron + Nucleus that contains protons Shell Electron Nucleus that contains protons and neutrons John Dalton J.J.Thomson James Chadwick Ernest Rutherford Neils Bohr 10
Example 4: The diagram shows the set-up of apparatus for the heating of copper(II) carbonate. Heat Copper(II) carbonate powder, CuCO3 Limewater (a) State the name and chemical formula of (i) reactants (ii) products (b) Write a balanced chemical equation for this reaction. Solution: (a) (i) Reactant: Copper(II) carbonate, CuCO3 (ii) Products: Copper(II) oxide, CuO, carbon dioxide gas, CO2 (b) CuCO3 (s) → CuO(s) + CO2 (g) 3.4 Chemical Equation Reactant Information from the equation: • 1 mole of solid copper(II) carbonate decomposes to form 1 mole of solid copper(II) oxide and 1 mole of carbon dioxide gas. Physical state Products 21
Reacts with water to form an acidic solution. Example: Cl2 + H2 O ⇌ HCl + HOCl • Hypochlorous acid has bleaching properties. • The solution formed turns blue litmus paper to red, then bleached. Reacts with an alkaline solution to form metal halide, metal halate and water. Example: Cl2 + 2NaOH → NaCl + NaOCl + H2 O Sodium Sodium chloride hypochlorite Reacts with metal to form metal halide. Example: 3Cl2 + 2Fe → 2FeCl3 Iron filings Combustion tube Dry chlorine gas, Cl2 Asbestos Heat paper Soda lime • Brown solid is formed. Chemical properties of Group 17 elements Halogen is toxic. All experiments using halogen must be carried out in the fume chamber. TIPS Function of soda lime is to absorb excess chlorine gas. TIPS 33
• Acid is a chemical substance that ionises in water to produce hydrogen ions, H+. • Basicity of acids is the number of H+ ions produced per acid molecule when acids dissolve in water. Monoprotic acid: Produce 1 H+ ion per acid molecule Diprotic acid: Produce 2 H+ ion per acid molecule Triprotic acid: Produce 3 H+ ion per acid molecule Example: HCl → H+ + Cl− CH3 COOH ⇌ CH3 COO− + H+ Example: H2 SO4 → 2H+ + SO4 2− Example: H3 PO4 → 3H+ + PO4 3− Basicity of acids • Base is a chemical substance that reacts with an acid to form salt and water only. Bases that dissolves in water is called an alkali. • Alkali is a chemical substance that ionises in water to produce hydroxide ions, OH−. CHAPTER 6 ACID, BASE AND SALT 6.1 The Role of Water in Showing Acidic and Alkaline Properties Theme: 3 49
Changes that occur during reactions 1 Increase in the volume of gas Example: CaCO3 + 2HCl → CaCl2 + H2 O + CO2 • The volume of carbon dioxide gas, CO2 increases as the reaction occurs. • The change in the gas volume is determined from the burette reading. • Rate of reaction can be measured in the unit of cm3 s−1 or cm3 min−1. 2 Decrease in the mass of the reactants Example: CaCO3 + 2HCl → CaCl2 + H2 O + CO2 • The mass of calcium carbonate, CaCO3 and hydrochloric acid, HCl decrease during the reaction. • The change in the mass is determined from the reading of the electronic balance. • Rate of reaction can be measured in the unit of g s−1 or g min−1. Burette Carbon dioxide gas, CO2 Hydrochloric acid, HCl Calcium carbonate, CaCO3 Conical flask Water Hydrochloric acid, HCl Cotton wool Marble chips, CaCO3 ON OFF g Electronic balance 78
CHAPTERS MANUFACTURED SUBSTANCES IN INDUSTRY 8 8.1 Alloy and Its Importance • An alloy is a substance consisting of a mixture of two or more elements in a fixed composition of which the main element is a metal. • Pure metal atoms are of the same size and arranged in an orderly arrangement. • When force is applied: (a) the layer of atoms in the metal can slide over each other easily causing it to be ductile. (b) Atoms in a pure metal also slide to fill up space between the atoms causing it to be malleable. • The size of foreign atoms which are different than the pure metal atoms disrupt the orderly arrangement of atoms in a pure metal. • This make it difficult for the layers of atoms to slide over each other when force is applied. • Hence, alloy is harder than pure metal. Foreign atom + Arrangement of atoms in an alloy Atom of pure metal Theme: 4 84
CHAPTER 1 REDOX EQUILIBRIUM 1.1 Oxidation and Reduction • Redox reaction is a chemical reaction in which oxidation and reduction occur simultaneously. • Oxidising agent is the substance that oxidises other substances but is reduced in the reaction. • Reducing agent is the substance that reduces other substances but is oxidised in the reaction. Oxidation Reduction Loss or gain of oxygen Gain oxygen Lose oxygen Loss or gain of hydrogen Lose hydrogen Gain hydrogen Transfer of electrons Lose electrons Gain electrons Change in oxidation number Increase in oxidation number Decrease in oxidation number Theme: 1 92
1.2 Standard Electrode Potential • Diagram shows how the electrode potential for hydrogen half-cell is produced when there is a potential difference between the electrode that is in contact with hydrogen gas and the solution containing hydrogen ions. • Scientists compare the value of electrode potential of an unknown half-cell with hydrogen electrode, the standard hydrogen electrode. • Electrode potential of standard hydrogen electrode, E0 is assigned as 0.00 V. • The electrode potential in a half-cell when compared relative to a standard hydrogen electrode, SHE under standard conditions is called standard electrode potential, E0 . • Standard conditions for the measurement of standard electrode potential of a half-cell: (a) Concentration of ions in aqueous solution is 1.0 mol dm–3 (b) All gases involved are at a pressure of 1 atm or 101 kPa (c) Temperature 25 °C or 298 K (d) Platinum as an inert electrode e– H+ H2 H2 H+ H+ H+ e– e– e– Platinum, Pt electrode atoms H2 (g) at 1 atm H2 (g) Platinum, Pt wire Platinum, Pt electrode Acidic solution, H+ 1.0 mol dm–3 Half-reaction at platinum, Pt surface: 2H+(aq) + 2e– H2 (g) 103
1.3 Voltaic Cell • A simple voltaic cell consists of two different metals that are connected to a bulb, voltmeter or galvanometer using connecting wires and placed in an electrolyte. • Potential difference between these two metals causes the movement of electrons through an external circuit (wire), producing an electric current. • Diagram shows a simple voltaic cell. Mg2+(aq) + 2e− ⇌ Mg(s) E0 = – 2.38 V Cu2+(aq) + 2e− ⇌ Cu(s) E0 = + 0.34 V • E0 magnesium value is more negative. Therefore, magnesium is a stronger reducing agent compared to copper. Redox reaction in a voltaic cell e– e– e– e– e– e– + + H+ H+ H2 Mg Mg 2+ e– e– e– e– 2 1 3 Magnesium electrode Copper electrode Current flow Wire Hydrogen gas bubble Bulb Sulphuric acid, H2 SO4 107
Daniell cell • Diagram shows a Daniell cell. Zn2+(aq) + 2e− ⇌ Zn(s) E0 = – 0.76 V Cu2+(aq) + 2e− ⇌ Cu(s) E0 = + 0.34 V • E0 zinc value is more negative. It indicates that zinc is a stronger reducing agent. Thus, zinc plate is an anode, where oxidation process occurs. • E0 copper is more positive. It indicates that the copper(II) ion, Cu2+ is an oxidising agent. Copper plate is the cathode, where reduction process occurs. e– e– SO4 2– SO4 2– Cl– V Zn2+ Cu2+ Na+ 2 1 3 Voltmeter Zinc (anode) Zinc sulphate, ZnSO4 1.0 mol dm–3 solution Copper(II) sulphate, CuSO4 1.0 mol dm–3 solution Copper (cathode) Salt bridge, sodium chloride NaCI 110
I The iron surface in the middle of the water droplet serves as the anode (negative terminal), where oxidation occurs. The iron atom is oxidised to Fe2+ ion by losing 2 electrons. Then, Fe2+ ion dissolves in water. Oxidation half-equation: Fe → Fe2+ + 2e− II The electrons released flow to the edge of a water droplet, where the concentration of oxygen is higher. The iron surface at the edge of the water droplet serves as the cathode (positive terminal), where reduction occurs. Anode (negative terminal) Fe(s) Fe2+(aq) + 2e– Cathode (positive terminal) O2 (g) + 2H2 O(l) + 4e– 4OH– (aq) O2 e– e– O2 Fe2+ Fe2+ Water droplets I II III IV Fe2 O3 ,xH2 O (rust) 133
CHAPTER 2 CARBON COMPOUND 2.1 Types of Carbon Compounds Carbon compounds Compounds that contain carbon as their constituent element. Organic compounds Compounds originating from living things Hydrocarbon Organic compounds contain only carbon and hydrogen. Non hydrocarbon Organic compounds contain carbon and hydrogen and other elements, such as oxygen, nitrogen, phosphorus or halogens. Example: Alcohol, ester, carboxylic acid Saturated hydrocarbon Hydrocarbons containing only single covalent bonds between carbon atoms. Example: Alkane Unsaturated hydrocarbon Hydrocarbons containing at least one double or triple covalent bond between carbon atoms. Example: Alkene, alkyne Inorganic compounds Compounds originating from non-living materials Theme: 2 137
Preparation of alcohols (example: ethanol) 1 Fermentation of glucose with yeast (b) Purification of ethanol by fractional distillation Delivery tube Rubber stopper Boiling tube Limewater Conical flask Glucose solution + yeast Thermometer Water out Liebig condenser Water in Fractionating column Filtrate Water Heat Ethanol, C2 H5 OH (a) Fermentation of glucose Glucose Ethanol + Carbon dioxide Zymase enzyme 2 Hydration of ethene with catalyst. Ethene + Steam Ethanol H3 PO4 300°C, 60 atm 148
CHAPTER 3 THERMOCHEMISTRY 3.1 Heat Change in Reactions There is a change of heat energy when a chemical reaction occurs. The change of heat energy occurs when the heat energy is released or the heat energy is absorbed Heat energy is given out when new bonds are formed in the products. Energy change in a chemical reaction A chemical reaction involves a change of heat energy, either heat energy released or absorbed. Heat energy is absorbed to break the bonds in the reactants. Theme: 3 155
Heat of neutralisation Steps to calculate heat of neutralisation 1. Calculate the number of moles of water produced Number of moles, n = MV 1000 2. Calculate the heat change Q = mcθ c = 4.2 J g−1 °C−1 3. Calculate the heat change for the formation of 1 mole of water Heat of neutralisation, ΔH = − The heat change, Q Number of moles = −P kJ mol−1 Example 3: 50 cm3 of 2.0 mol dm−3 sodium hydroxide solution, NaOH was mixed with 50 cm3 of 2.0 mol dm−3 hydrochloric acid, HCI. The highest temperature of the mixed solution is 43 °C. The initial temperature of the hydrochloric acid, HCI is 28°C and sodium hydroxide solution, NaOH is 29 °C. Calculate the heat of neutralisation. [Specific heat capacity of solution, c = 4.2 J g−1 °C−1; density of solution = 1 g cm−3] 28 °C 29 °C 43 °C 50 cm3 of 2.0 mol dm–3 hydrochloric acid 50 cm3 of 2.0 mol dm–3 sodium hydroxide solution Mixed solution 166
1 When pants are immersed in water, the pants are almost wet but there are water droplets that surround the grease. Greasy stain Cleaning agent Water molecule Fabric Grease Water droplet Surface tension of water Soap/detergent – – + + – – – – – + + + + + – – – Fabric Grease Cation Water molecule Anion of soap/detergent + 3 The hydrophilic part of the soap/detergent anion dissolves in water whereas the hydrophobic part of the soap/detergent anion dissolves in grease. 2 When soap/detergent is added to water, soap/detergent ionises in water to become soap/detergent anions and cations. These soap/detergent anions squeeze through the water droplets. Hence, soap/detergent helps to reduce the surface tension of water and the fabric turns wet thoroughly. – – – – – – – – – – – – – – Fabric Grease + + + + The cleansing action of soap and detergent 195
• Graphene is one of the carbon allotropes that looks like a sheet which is a one-atom thick crystalline form of carbon. • The carbon atoms are held together by covalent bonds in a two-dimensional honeycomb lattice. Graphene Covalent bond Carbon atom Very high tensile strength High thermal and electrical conductivity World’s strongest material (stronger than diamond) Very elastic and flexible Transparent and biocompatibility Impermeable Physical properties of graphene • Chemical properties of graphene: (a) Burn at a lower temperature than graphite. (b) It is the most reactive carbon allotropes. 211
topsoil Sand Clay Garbage Probes to detect methane leaks Methane gas recovery Methane stroage and compressor building Electricity generator building Leachate treatment system Pipe collect explosive methane gas used as fuel to generate electricity Groundwater monitoring well Leachate monitoring well Groundwater Leachate pumped up to storage tanks for safe disposal Sanitary landfills Leachate storage tank Leachate pipes Compacted solid waste Garbage Sand Synthetic liner Sand Clay Subsoil When landfill is full layers of soil and clay seal in trash Clay and plastic lining to prevent leaks; pipes collect leachate from bottom of landfill 216