CHLORINE AND ITS COMPOUNDS

Introduction and Preparation of Chlorine

By the end of the lesson, the learner should be able to:
Define chlorine and state its position in the periodic table. Describe the occurrence of chlorine in nature. Describe laboratory preparation of chlorine gas. Write balanced equations for chlorine preparation.

Q/A: Review Group VII elements and electron configuration of chlorine ( 8.7). Discussion: Occurrence as sodium chloride in sea water and rock salt. Practical work: Experiment 6.1 - Preparation using MnO2 + concentrated HCl. Setup apparatus as in Figure 6. Safety precautions for handling chlorine gas.

Manganese(IV) oxide, Concentrated HCl, Gas collection apparatus, Water, Concentrated H2SO4, Blue litmus paper, Gas jars

KLB Secondary Chemistry Form 4, Pages 195-196

CHLORINE AND ITS COMPOUNDS

Physical Properties of Chlorine
Chemical Properties of Chlorine - Reaction with Water

By the end of the lesson, the learner should be able to:
Investigate the physical properties of chlorine gas. Explain the method of collection used for chlorine. Test the solubility of chlorine in water. State the density and color of chlorine gas.

Practical work: Experiment 6.2 - Testing chlorine gas preserved from previous experiment. Recording observations in Table 6. Testing: Color, smell (caution - no direct smelling), density, solubility in water. Demonstration: Inverting gas jar in water trough. Discussion: Why collected by downward delivery.

Preserved chlorine gas, Water trough, Gas jars, Observation tables, Safety equipment
Chlorine gas, Distilled water, Blue and red litmus papers, Colored flower petals, Gas jars, Boiling tubes

KLB Secondary Chemistry Form 4, Pages 196-197

CHLORINE AND ITS COMPOUNDS

Chemical Properties of Chlorine - Reaction with Metals
Chemical Properties of Chlorine - Reaction with Non-metals

By the end of the lesson, the learner should be able to:
Investigate reactions of chlorine with metals. Write balanced equations for metal-chlorine reactions. Explain the formation of metal chlorides. Demonstrate exothermic nature of these reactions.

Practical work: Experiment 6.4 - Reactions with burning magnesium, hot iron wire, dry chlorine over hot iron coil (Figure 6.2). Recording observations in Table 6. Observations: White fumes (MgCl2), glowing iron wire, black crystals (FeCl3). Discussion: Formation of higher oxidation state chlorides. Safety: Proper ventilation and eye protection.

Magnesium ribbon, Iron wire, Chlorine gas, Deflagrating spoon, Combustion tube, Anhydrous CaCl2, Gas jars
Red phosphorus, Hydrogen gas, Chlorine gas, Deflagrating spoon, Gas jars, Bunsen burner, Safety equipment

KLB Secondary Chemistry Form 4, Pages 199-201

CHLORINE AND ITS COMPOUNDS

Oxidising Properties of Chlorine
Reaction of Chlorine with Alkali Solutions

By the end of the lesson, the learner should be able to:
Investigate chlorine as an oxidizing agent. Test reactions with reducing agents. Write ionic equations for redox reactions. Identify color changes in oxidation reactions.

Practical work: Experiment 6.6 - Bubbling chlorine through sodium sulphite solution, testing with barium nitrate and lead nitrate. Reactions with hydrogen sulphide and ammonia. Recording observations in Table 6. Color changes and precipitate formation. Writing ionic equations: SO3²⁻ + Cl2 + H2O → SO4²⁻ + 2Cl⁻ + 2H⁺.

Sodium sulphite solution, Barium nitrate, Lead nitrate, Hydrogen sulphide gas, Aqueous ammonia, Chlorine gas, Test tubes
Sodium hydroxide solutions (dilute cold, concentrated hot), Chlorine gas, Beakers, Bunsen burner, Thermometer

KLB Secondary Chemistry Form 4, Pages 201-202

CHLORINE AND ITS COMPOUNDS

Oxidising Properties - Displacement Reactions
Test for Chloride Ions
Uses of Chlorine and its Compounds

By the end of the lesson, the learner should be able to:
Investigate displacement reactions of chlorine with halides. Test reactions with bromides and iodides. Write ionic equations for displacement reactions. Explain the order of reactivity of halogens.
List the industrial uses of chlorine. Explain the use of chlorine in water treatment. Describe manufacture of chlorine compounds. Relate properties to uses of chlorine.

Practical work: Experiment 6.8 - Bubbling chlorine through potassium bromide and potassium iodide solutions. Observations: Colorless to orange (Br2), colorless to brown (I2). Writing ionic equations: Cl2 + 2Br⁻ → 2Cl⁻ + Br2, Cl2 + 2I⁻ → 2Cl⁻ + I Discussion: Displacement as evidence of relative reactivity.
Discussion: Industrial applications - HCl manufacture, bleaching agents for cotton and paper industries, water treatment and sewage plants. Study Figure 6.3(a) - bleaching chemicals. Applications: Chloroform (anaesthetic), solvents (trichloroethane), CFCs, PVC plastics, pesticides (DDT), germicides and fungicides. Q/A: Relating chemical properties to practical applications.

Potassium bromide solution, Potassium iodide solution, Chlorine gas, Test tubes, Observation charts
Sodium chloride, Concentrated H2SO4, Lead(II) nitrate solution, Aqueous ammonia, Glass rod, Test tubes, Bunsen burner
Charts showing industrial uses, Samples of bleaching agents, PVC materials, Photographs of water treatment plants, Industrial application diagrams

KLB Secondary Chemistry Form 4, Pages 203-204
KLB Secondary Chemistry Form 4, Pages 205-207

CHLORINE AND ITS COMPOUNDS

Hydrogen Chloride - Laboratory Preparation

By the end of the lesson, the learner should be able to:
Describe laboratory preparation of hydrogen chloride gas. Set up apparatus for HCl preparation. Investigate physical properties of HCl gas. Explain the method of collection used.

Practical work: Experiment 6.10 - Preparation using rock salt (NaCl) + concentrated H2SO Setup apparatus as in Figure 6.3(b). Testing physical properties and recording in Table 6.6. Tests: Solubility (fountain experiment), reaction with ammonia, effect on litmus. Collection by downward delivery due to density. Writing equation: NaCl + H2SO4 → NaHSO4 + HCl.

Rock salt (NaCl), Concentrated H2SO4, Gas collection apparatus, Ammonia solution, Litmus papers, Water trough, Gas jars

KLB Secondary Chemistry Form 4, Pages 207-208

CHLORINE AND ITS COMPOUNDS

Chemical Properties of Hydrogen Chloride

By the end of the lesson, the learner should be able to:
Prepare aqueous hydrogen chloride (hydrochloric acid). Investigate acid properties of HCl solution. Test reactions with metals, bases, and carbonates. Compare HCl in water vs organic solvents.

Practical work: Experiment 6.11 - Preparation of aqueous HCl using apparatus in Figure 6. Testing with metals (Zn, Fe, Mg, Cu), NaOH, carbonates, lead nitrate. Recording observations in Table 6.7. Testing HCl in methylbenzene - no acid properties. Discussion: Ionization in water vs molecular existence in organic solvents. Writing equations for acid reactions.

Distilled water, Filter funnel, Metals (Zn, Fe, Mg, Cu), NaOH solution, Carbonates, Lead nitrate, Methylbenzene, Indicators

KLB Secondary Chemistry Form 4, Pages 208-211

CHLORINE AND ITS COMPOUNDS

Large-scale Manufacture of Hydrochloric Acid

By the end of the lesson, the learner should be able to:
Describe industrial production of hydrochloric acid. Identify raw materials and conditions used. Explain the controlled combustion process. Draw flow diagrams of the industrial process.

Study of Figure 6.4 - Large-scale manufacture setup. Discussion: Raw materials (H2 from electrolysis/cracking, Cl2 from electrolysis). Controlled combustion: H2 + Cl2 → 2HCl in jet burner. Dissolving HCl gas in water over glass beads. Safety: Explosive nature of H2/Cl2 mixture, use of excess chlorine. Industrial considerations: 35% concentration, transport in rubber-lined steel tanks.

Flow diagrams, Industrial photographs, Glass beads samples, Charts showing electrolysis processes, Safety equipment models

KLB Secondary Chemistry Form 4, Pages 211-212

CHLORINE AND ITS COMPOUNDS

Uses of Hydrochloric Acid
Environmental Pollution by Chlorine Compounds and Summary

By the end of the lesson, the learner should be able to:
List the industrial uses of hydrochloric acid. Explain applications in metal treatment. Describe use in water treatment and manufacturing. Relate acid properties to industrial applications.
Explain environmental effects of chlorine compounds. Describe the impact of CFCs on ozone layer. Discuss pollution by chlorine-containing pesticides. Summarize key concepts of chlorine chemistry.

Discussion: Applications - rust removal and descaling, galvanizing preparation, electroplating preparation, water treatment (chlorination), sewage treatment. Manufacturing uses: dyes, drugs, photographic materials (AgCl), pH control in industries. Q/A: How acid properties make HCl suitable for these uses. Case studies: Metal cleaning processes, water purification systems.
Discussion: Environmental impacts - chlorine gas forming acid rain, CFCs (life span CCl3F = 75 years, CCl2F2 = 110 years) breaking down ozone layer. DDT as persistent pesticide, PVC as non-biodegradable plastic. NEMA role in environmental protection, Stockholm Convention on DDT. Control measures and alternatives. Revision: Key reactions, properties, uses, and environmental considerations. Summary of halogen chemistry concepts.

Samples of rusted and cleaned metals, Photographic materials, pH control charts, Industrial application videos, Water treatment diagrams
Environmental pollution charts, Ozone layer diagrams, DDT restriction documents, PVC waste samples, NEMA guidelines, Summary charts of reactions

KLB Secondary Chemistry Form 4, Pages 212-213
KLB Secondary Chemistry Form 4, Pages 213-215

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Endothermic and Exothermic Reactions

By the end of the lesson, the learner should be able to:
- Define endothermic and exothermic reactions using ΔH notation
-Investigate temperature changes when ammonium nitrate and sodium hydroxide dissolve in water
-Explain observations made during dissolution
-Draw energy level diagrams for endothermic and exothermic reactions

Class experiment: Wrap 250ml plastic beakers with tissue paper. Dissolve 2 spatulafuls of NH₄NO₃ in 100ml distilled water, record temperature changes. Repeat with NaOH pellets. Compare initial and final temperatures. Draw energy level diagrams showing relative energies of reactants and products.

250ml plastic beakers, tissue paper, rubber bands, NH₄NO₃, NaOH pellets, distilled water, thermometers, spatulas, measuring cylinders

KLB Secondary Chemistry Form 4, Pages 29-31

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Enthalpy Notation and Energy Content

By the end of the lesson, the learner should be able to:
- Define enthalpy and enthalpy change
-Use the symbol ΔH to represent enthalpy changes
-Calculate enthalpy changes using the formula ΔH = H(products) - H(reactants)
-Distinguish between positive and negative enthalpy changes

Q/A: Review previous experiment results. Introduce enthalpy symbol H and enthalpy change ΔH. Calculate enthalpy changes from previous experiments. Explain why endothermic reactions have positive ΔH and exothermic reactions have negative ΔH. Practice calculations with worked examples.

Student books, calculators, worked examples from textbook, chalkboard for calculations

KLB Secondary Chemistry Form 4, Pages 31-32

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Bond Breaking and Bond Formation

By the end of the lesson, the learner should be able to:
- Explain that energy changes are due to bond breaking and bond formation
-Describe bond breaking as endothermic and bond formation as exothermic
-Investigate energy changes during melting and boiling
-Plot heating curves for pure substances

Class experiment: Heat crushed ice while stirring with thermometer. Record temperature every minute until ice melts completely, then continue until water boils. Plot temperature-time graph. Explain constant temperature during melting and boiling in terms of bond breaking. Discuss latent heat of fusion and vaporization.

Crushed pure ice, 250ml glass beakers, thermometers, heating source, stopwatch, graph paper, stirring rods

KLB Secondary Chemistry Form 4, Pages 32-35

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Latent Heat of Fusion and Vaporization
Bond Energy Calculations

By the end of the lesson, the learner should be able to:
- Define latent heat of fusion and molar heat of fusion
-Define latent heat of vaporization and molar heat of vaporization
-Explain why temperature remains constant during phase changes
-Relate intermolecular forces to melting and boiling points
- Calculate energy changes in reactions using bond energies
-Apply the formula: Heat of reaction = Bond breaking energy + Bond formation energy
-Determine whether reactions are exothermic or endothermic
-Use bond energy data to solve problems

Discussion based on previous heating curve experiment. Explain energy used to overcome intermolecular forces during melting and boiling. Compare molar heats of fusion and vaporization for water and ethanol. Relate strength of intermolecular forces to magnitude of latent heats. Calculate energy required for phase changes.
Work through formation of HCl from H₂ and Cl₂ using bond energies. Calculate energy required to break H-H and Cl-Cl bonds. Calculate energy released when H-Cl bonds form. Apply formula: ΔH = Energy absorbed - Energy released. Practice with additional examples. Discuss why calculated values may differ from experimental values.

Data tables showing molar heats of fusion/vaporization, calculators, heating curves from previous lesson
Bond energy data tables, calculators, worked examples, practice problems

KLB Secondary Chemistry Form 4, Pages 32-35
KLB Secondary Chemistry Form 4, Pages 35-36

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Determination of Enthalpy of Solution I

By the end of the lesson, the learner should be able to:
- Determine the enthalpy changes of solution of ammonium nitrate and sodium hydroxide
-Calculate enthalpy change using ΔH = mcΔT
-Calculate number of moles of solute dissolved
-Determine molar heat of solution

Class experiment: Dissolve exactly 2.0g NH₄NO₃ in 100ml distilled water in plastic beaker. Record temperature change. Repeat with 2.0g NaOH. Calculate enthalpy changes using ΔH = mcΔT where m = 100g, c = 4.2 kJ kg⁻¹K⁻¹. Calculate moles dissolved and molar heat of solution.

250ml plastic beakers, 2.0g samples of NH₄NO₃ and NaOH, distilled water, thermometers, measuring cylinders, analytical balance, calculators

KLB Secondary Chemistry Form 4, Pages 36-38

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Thermochemical Equations

By the end of the lesson, the learner should be able to:
- Write thermochemical equations including enthalpy changes
-Define molar heat of solution
-Draw energy level diagrams for dissolution reactions
-Interpret thermochemical equations correctly

Using data from previous experiment, write thermochemical equations for NH₄NO₃ and NaOH dissolution. Show proper notation with state symbols and ΔH values. Draw corresponding energy level diagrams. Practice writing thermochemical equations for various reactions. Explain significance of molar quantities in equations.

Results from previous experiment, graph paper for energy level diagrams, practice examples

KLB Secondary Chemistry Form 4, Pages 38-39

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Enthalpy of Solution of Concentrated Sulphuric Acid

By the end of the lesson, the learner should be able to:
- Determine heat of solution of concentrated sulphuric(VI) acid
-Apply safety precautions when handling concentrated acids
-Calculate enthalpy change considering density and purity
-Write thermochemical equation for the reaction

Teacher demonstration: Carefully add 2cm³ concentrated H₂SO₄ to 98cm³ distilled water in wrapped beaker (NEVER vice versa). Record temperature change. Calculate mass of acid using density (1.84 g/cm³) and purity (98%). Calculate molar heat of solution. Emphasize safety - always add acid to water.

Concentrated H₂SO₄, distilled water, 250ml plastic beaker, tissue paper, measuring cylinders, thermometer, safety equipment

KLB Secondary Chemistry Form 4, Pages 39-41

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Enthalpy of Combustion
Enthalpy of Displacement

By the end of the lesson, the learner should be able to:
- Define molar heat of combustion
-Determine enthalpy of combustion of ethanol experimentally
-Explain why experimental values differ from theoretical values
-Calculate molar enthalpy of combustion from experimental data
- Define molar heat of displacement
-Investigate displacement of copper(II) ions by zinc
-Calculate molar heat of displacement
-Explain relationship between position in reactivity series and heat of displacement

Class experiment: Burn ethanol in small bottle with wick to heat 100cm³ water in glass beaker. Record initial and final masses of bottle+ethanol and temperature change. Calculate moles of ethanol burned and heat evolved. Determine molar enthalpy of combustion. Compare with theoretical value (-1368 kJ/mol). Discuss sources of error.
Class experiment: Add 4.0g zinc powder to 100cm³ of 0.5M CuSO₄ solution in wrapped plastic beaker. Record temperature change and observations. Calculate moles of Zn used and Cu²⁺ displaced. Determine molar heat of displacement. Write ionic equation. Discuss why excess zinc is used. Compare with theoretical value.

Ethanol, small bottles with wicks, 250ml glass beakers, tripod stands, wire gauze, thermometers, analytical balance, measuring cylinders
Zinc powder, 0.5M CuSO₄ solution, 250ml plastic beakers, tissue paper, thermometers, analytical balance, stirring rods

KLB Secondary Chemistry Form 4, Pages 41-44
KLB Secondary Chemistry Form 4, Pages 44-47

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Enthalpy of Neutralization

By the end of the lesson, the learner should be able to:
- Define molar heat of neutralization
-Determine heat of neutralization of HCl with NaOH
-Compare neutralization enthalpies of strong and weak acids/bases
-Write ionic equations for neutralization reactions

Class experiment: Mix 50cm³ of 2M HCl with 50cm³ of 2M NaOH in wrapped beaker. Record temperature changes. Calculate molar heat of neutralization. Repeat with weak acid (ethanoic) and weak base (ammonia). Compare values. Write ionic equations. Explain why strong acid + strong base gives ~57.2 kJ/mol.

2M HCl, 2M NaOH, 2M ethanoic acid, 2M ammonia solution, measuring cylinders, thermometers, 250ml plastic beakers, tissue paper

KLB Secondary Chemistry Form 4, Pages 47-49

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Standard Conditions and Standard Enthalpy Changes

By the end of the lesson, the learner should be able to:
- Identify standard conditions for measuring enthalpy changes
-Define standard enthalpy changes using ΔH° notation
-Explain importance of standard conditions
-Use subscripts to denote different types of enthalpy changes

Q/A: Review previous enthalpy measurements. Introduce standard conditions: 25°C (298K) and 1 atmosphere pressure (101.325 kPa). Explain ΔH° notation and subscripts (ΔH°c for combustion, ΔH°f for formation, etc.). Discuss why standard conditions are necessary for comparison. Practice using correct notation.

Student books, examples of standard enthalpy data, notation practice exercises

KLB Secondary Chemistry Form 4, Pages 49

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Hess's Law - Introduction and Theory

By the end of the lesson, the learner should be able to:
- State Hess's Law
-Explain the principle of energy conservation in chemical reactions
-Understand that enthalpy change is independent of reaction route
-Apply Hess's Law to simple examples

Introduce Hess's Law: "The energy change in converting reactants to products is the same regardless of the route by which the chemical change occurs." Use methane formation example to show two routes giving same overall energy change. Draw energy cycle diagrams. Explain law of conservation of energy application.

Energy cycle diagrams for methane formation, chalkboard illustrations, worked examples from textbook

KLB Secondary Chemistry Form 4, Pages 49-52

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Energy Cycle Diagrams
Hess's Law Calculations
Lattice Energy and Hydration Energy

By the end of the lesson, the learner should be able to:
- Draw energy cycle diagrams
-Link enthalpy of formation with enthalpy of combustion
-Calculate unknown enthalpy changes using energy cycles
-Apply Hess's Law to determine enthalpy of formation
- Solve complex problems using Hess's Law
-Apply energy cycles to multi-step reactions
-Calculate enthalpy of formation from combustion data
-Use thermochemical equations in Hess's Law problems

Work through energy cycle for formation of CO from carbon and oxygen using combustion data. Draw cycle showing Route 1 (direct combustion) and Route 2 (formation then combustion). Calculate ΔH°f(CO) = ΔH°c(C) - ΔH°c(CO). Practice with additional examples including ethanol formation.
Work through detailed calculation for ethanol formation: 2C(s) + 3H₂(g) + ½O₂(g) → C₂H₅OH(l). Use combustion enthalpies of carbon (-393 kJ/mol), hydrogen (-286 kJ/mol), and ethanol (-1368 kJ/mol). Calculate ΔH°f(ethanol) = -278 kJ/mol. Practice with propane and other compounds.

Graph paper, energy cycle templates, combustion data tables, calculators
Worked examples, combustion data, calculators, step-by-step calculation sheets
Energy cycle diagrams, lattice energy and hydration energy data tables, calculators

KLB Secondary Chemistry Form 4, Pages 52-54
KLB Secondary Chemistry Form 4, Pages 54-56

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Factors Affecting Lattice and Hydration Energies

By the end of the lesson, the learner should be able to:
- Explain factors affecting lattice energy
-Explain factors affecting hydration energy
-Use data tables to identify trends
-Calculate enthalpies of solution for various ionic compounds

Analyze data tables showing lattice energies (Table 2.7) and hydration energies (Table 2.6). Identify trends: smaller ions and higher charges give larger lattice energies and hydration energies. Calculate heat of solution for MgCl₂ using: ΔH(solution) = +2489 + (-1891 + 2×(-384)) = -170 kJ/mol. Practice with other compounds.

Data tables from textbook, calculators, trend analysis exercises

KLB Secondary Chemistry Form 4, Pages 54-56

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Definition and Types of Fuels

By the end of the lesson, the learner should be able to:
- Define a fuel
-Classify fuels as solid, liquid, or gaseous
-State examples of each type of fuel
-Explain energy conversion in fuel combustion

Q/A: List fuels used at home and school. Define fuel as "substance that produces useful energy when it undergoes chemical or nuclear reaction." Classify examples: solids (coal, charcoal, wood), liquids (petrol, kerosene, diesel), gases (natural gas, biogas, LPG). Discuss energy conversions during combustion.

Examples of different fuels, classification charts, pictures of fuel types

KLB Secondary Chemistry Form 4, Pages 56

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Heating Values of Fuels

By the end of the lesson, the learner should be able to:
- Define heating value of a fuel
-Calculate heating values from molar enthalpies of combustion
-Compare heating values of different fuels
-Explain units of heating value (kJ/g)

Calculate heating value of ethanol: ΔH°c = -1360 kJ/mol, Molar mass = 46 g/mol, Heating value = 1360/46 = 30 kJ/g. Compare heating values from Table 2.8: methane (55 kJ/g), fuel oil (45 kJ/g), charcoal (33 kJ/g), wood (17 kJ/g). Discuss significance of these values for fuel selection.

Heating value data table, calculators, fuel comparison charts

KLB Secondary Chemistry Form 4, Pages 56-57

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Factors in Fuel Selection
Environmental Effects of Fuels

By the end of the lesson, the learner should be able to:
- State factors that influence choice of fuel
-Explain why different fuels are chosen for different purposes
-Compare advantages and disadvantages of various fuels
-Apply selection criteria to real situations
- Identify environmental effects of burning fuels
-Explain formation and effects of acid rain
-Describe contribution to global warming
-State measures to reduce pollution from fuels

Discuss seven factors: heating value, ease of combustion, availability, transportation, storage, environmental effects, cost. Compare wood/charcoal for domestic use vs methylhydrazine for rockets. Analyze why each is suitable for its purpose. Students suggest best fuels for cooking, heating, transport in their area.
Discuss pollutants from fossil fuels: SO₂, SO₃, CO, NO₂ causing acid rain. Effects: damage to buildings, corrosion, acidification of lakes, soil leaching. CO₂ and hydrocarbons cause global warming leading to ice melting, climate change. Pollution reduction measures: catalytic converters, unleaded petrol, zero emission vehicles, alternative fuels.

Fuel comparison tables, local fuel availability data, cost analysis sheets
Pictures of environmental damage, pollution data, examples of clean technology

KLB Secondary Chemistry Form 4, Pages 57
KLB Secondary Chemistry Form 4, Pages 57-58

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Fuel Safety and Precautions

By the end of the lesson, the learner should be able to:
- State precautions necessary when using fuels
-Explain safety measures for different fuel types
-Identify hazards associated with improper fuel handling
-Apply safety principles to local situations

Discuss safety precautions: ventilation for charcoal stoves (CO poisoning), not running engines in closed garages, proper gas cylinder storage, fuel storage away from populated areas, keeping away from fuel spills. Relate to local situations and accidents. Students identify potential hazards in their environment.

Safety guideline charts, examples of fuel accidents, local safety case studies

KLB Secondary Chemistry Form 4, Pages 57-58

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Endothermic and Exothermic Reactions

By the end of the lesson, the learner should be able to:
- Define endothermic and exothermic reactions using the ΔH notation
-Investigate what happens when ammonium nitrate and sodium hydroxide are separately dissolved in water
-Define enthalpy and enthalpy change
-Calculate enthalpy changes using ΔH = H(products) - H(reactants)

Class experiment: Dissolve NH₄NO₃ and NaOH separately in water, record temperature changes in Table 2.1. Explain heat absorption vs evolution. Introduce enthalpy (H) and enthalpy change (ΔH). Calculate enthalpy changes from experimental data. Draw energy level diagrams showing relative energies.

250ml plastic beakers, tissue paper, NH₄NO₃, NaOH pellets, distilled water, thermometers, calculators

KLB Secondary Chemistry Form 4, Pages 29-32

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES

Bond Breaking, Formation and Phase Changes

By the end of the lesson, the learner should be able to:
- Explain that energy changes are due to bond breaking and bond formation
-Investigate energy changes when solids and liquids are heated
-Define latent heat of fusion and vaporization
-Calculate energy changes using bond energies

Class experiment: Heat ice to melting then boiling, record temperature every minute. Plot heating curve. Explain constant temperature periods. Define latent heat of fusion/vaporization. Calculate energy changes in H₂ + Cl₂ → 2HCl using bond energies. Apply formula: ΔH = Energy absorbed - Energy released.

Ice, glass beakers, thermometers, heating source, graph paper, bond energy data tables

KLB Secondary Chemistry Form 4, Pages 32-36

ENERGY CHANGES IN PHYSICAL AND CHEMICAL PROCESSES
ACIDS, BASES AND SALTS

Determination of Enthalpy of Solution
Definition of Acids
Strength of Acids

By the end of the lesson, the learner should be able to:
- Carry out experiments to determine enthalpy changes of solution
-Calculate enthalpy change using ΔH = mcΔT
-Write correct thermochemical equations
-Define molar heat of solution
- Define an acid in terms of hydrogen ions
-Investigate reactions of magnesium and zinc carbonate with different acids
-Write equations for reactions taking place
-Explain why magnesium strip should be cleaned

Class experiment: Dissolve exactly 2.0g NH₄NO₃ and 2.0g NaOH separately in 100ml water. Record temperature changes. Calculate enthalpy changes using ΔH = mcΔT. Calculate moles and molar heat of solution. Write thermochemical equations: NH₄NO₃(s) + aq → NH₄NO₃(aq) ΔH = +25.2 kJ mol⁻¹.
Class experiment: React cleaned magnesium strips with 2M HCl, 2M ethanoic acid, 2M H₂SO₄, 2M ethanedioic acid. Record observations in table. Repeat using zinc carbonate. Write chemical equations. Discuss hydrogen ion displacement and gas evolution.

2.0g samples of NH₄NO₃ and NaOH, plastic beakers, thermometers, analytical balance, calculators
Magnesium strips, zinc carbonate, 2M HCl, 2M ethanoic acid, 2M H₂SO₄, 2M ethanedioic acid, test tubes, test tube rack
2M HCl, 2M ethanoic acid, universal indicator, pH chart, electrical conductivity apparatus, milliammeter, carbon electrodes, beakers, wires

KLB Secondary Chemistry Form 4, Pages 36-39
KLB Secondary Chemistry Form 4, Pages 1-3

ACIDS, BASES AND SALTS

Definition of Bases
Strength of Bases

By the end of the lesson, the learner should be able to:
- Define a base in terms of hydroxide ions
-Investigate effect of calcium hydroxide in water
-Test solutions with litmus paper
-Explain dissociation of bases in water

Teacher demonstration: Place dry calcium hydroxide on dry red litmus paper. Dissolve calcium hydroxide in water, test with litmus paper and phenolphthalein. Discuss observations and write dissociation equation. Define bases in terms of OH⁻ ions.

Calcium hydroxide, red litmus paper, phenolphthalein indicator, distilled water, test tubes, spatula, evaporating dish
2M NaOH, 2M ammonia solution, universal indicator, pH chart, electrical conductivity apparatus, milliammeter, carbon electrodes

KLB Secondary Chemistry Form 4, Pages 5-6

ACIDS, BASES AND SALTS

Acid-Base Reactions
Effect of Solvent on Acids
Effect of Solvent on Bases

By the end of the lesson, the learner should be able to:
- Write equations for acid-base reactions
-Explain neutralization process
-Identify products of acid-base reactions
-Demonstrate formation of salt and water

Q/A: Review acid and base definitions. Demonstrate neutralization reactions: HCl + NaOH, H₂SO₄ + Ca(OH)₂, HNO₃ + KOH. Write molecular and ionic equations. Explain H⁺ + OH⁻ → H₂O. Discuss salt formation. Use indicators to show neutralization point.

Various acids and bases from previous lessons, indicators, beakers, measuring cylinders, stirring rods
HCl gas, distilled water, methylbenzene, magnesium ribbon, calcium carbonate, litmus paper, test tubes, gas absorption apparatus
Dry ammonia gas, distilled water, methylbenzene, red litmus paper, test tubes, gas collection apparatus

KLB Secondary Chemistry Form 4, Pages 6-7

ACIDS, BASES AND SALTS

Amphoteric Oxides and Hydroxides
Definition of Salts and Precipitation

By the end of the lesson, the learner should be able to:
- Define amphoteric oxides
-Identify some amphoteric oxides
-Investigate reactions with both acids and alkalis
-Write equations for amphoteric behavior

Class experiment: React Al₂O₃, ZnO, PbO, Zn(OH)₂, Al(OH)₃, Pb(OH)₂ with 2M HNO₃ and 2M NaOH. Warm mixtures. Record observations in table. Write equations showing basic and acidic behavior. Discuss dual nature of amphoteric substances.

Al₂O₃, ZnO, PbO, Zn(OH)₂, Al(OH)₃, Pb(OH)₂, 2M HNO₃, 2M NaOH, boiling tubes, heating source
Na₂CO₃ solution, salt solutions containing various metal ions, test tubes, droppers

KLB Secondary Chemistry Form 4, Pages 10-11

ACIDS, BASES AND SALTS

Solubility of Chlorides, Sulphates and Sulphites
Complex Ions Formation

By the end of the lesson, the learner should be able to:
- Find out cations that form insoluble chlorides, sulphates and sulphites
-Write ionic equations for formation of insoluble salts
-Distinguish between sulphate and sulphite precipitates
-Investigate effect of warming on precipitates
- Explain formation of complex ions
-Investigate reactions with excess sodium hydroxide and ammonia
-Identify metal ions that form complex ions
-Write equations for complex ion formation

Class experiment: Add NaCl, Na₂SO₄, Na₂SO₃ to solutions of Pb²⁺, Ba²⁺, Mg²⁺, Ca²⁺, Zn²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Al³⁺. Warm mixtures. Record observations in table. Test sulphite precipitates with dilute HCl. List soluble and insoluble salts.
Class experiment: Add NaOH dropwise then in excess to Mg²⁺, Ca²⁺, Zn²⁺, Al³⁺, Cu²⁺, Fe²⁺, Fe³⁺, Pb²⁺ solutions. Repeat with NH₃ solution. Record observations showing precipitate formation and dissolution. Write equations for complex ion formation: [Zn(OH)₄]²⁻, [Al(OH)₄]⁻, [Pb(OH)₄]²⁻, [Zn(NH₃)₄]²⁺, [Cu(NH₃)₄]²⁺.

2M NaCl, 2M Na₂SO₄, 2M Na₂SO₃, 0.1M salt solutions, dilute HCl, test tubes, heating source
2M NaOH, 2M NH₃ solution, 0.5M salt solutions, test tubes, droppers

KLB Secondary Chemistry Form 4, Pages 14-16
KLB Secondary Chemistry Form 4, Pages 15-16

ACIDS, BASES AND SALTS

Solubility and Saturated Solutions

By the end of the lesson, the learner should be able to:
- Define the term solubility
-Determine solubility of a given salt at room temperature
-Calculate mass of solute and solvent
-Express solubility in different units

Class experiment: Weigh evaporating dish and watch glass. Measure 20cm³ saturated KNO₃ solution. Record temperature. Evaporate to dryness carefully. Calculate masses of solute, solvent, and solution. Determine solubility per 100g water and in moles per litre. Discuss definition and significance.

Saturated KNO₃ solution, evaporating dish, watch glass, measuring cylinder, thermometer, balance, heating source

KLB Secondary Chemistry Form 4, Pages 16-18

ACIDS, BASES AND SALTS

Effect of Temperature on Solubility

By the end of the lesson, the learner should be able to:
- Investigate the effect of temperature on solubility of potassium chlorate
-Record temperature at which crystals appear
-Calculate solubility at different temperatures
-Plot solubility curve

Class experiment: Dissolve 4g KClO₃ in 15cm³ water by warming. Cool while stirring and note crystallization temperature. Add 5cm³ water portions and repeat until total volume is 40cm³. Calculate solubility in g/100g water for each temperature. Plot solubility vs temperature graph.

KClO₃, measuring cylinders, thermometer, burette, boiling tubes, heating source, graph paper

KLB Secondary Chemistry Form 4, Pages 18-20

ACIDS, BASES AND SALTS

Solubility Curves and Applications

By the end of the lesson, the learner should be able to:
- Plot solubility curves for various salts
-Use solubility curves to determine mass of crystals formed
-Apply solubility curves to practical problems
-Compare solubility patterns of different salts

Using data from textbook, plot solubility curves for KNO₃, KClO₃, NaCl, CaSO₄. Calculate mass of crystals deposited when saturated solutions are cooled. Work through examples: KClO₃ cooled from 70°C to 30°C. Discuss applications in salt extraction and purification.

Graph paper, ruler, pencil, calculator, data tables from textbook

KLB Secondary Chemistry Form 4, Pages 20-21

ACIDS, BASES AND SALTS

Fractional Crystallization
Hardness of Water - Investigation

By the end of the lesson, the learner should be able to:
- Define fractional crystallization
-Apply knowledge of solubility curves in separation of salts
-Calculate masses of salts that crystallize
-Explain separation of salt mixtures
- Determine the effects of various salt solutions on soap
-Identify cations that cause hardness
-Distinguish between hard and soft water
-Investigate effect of boiling on water hardness

Work through separation problems using solubility data for KNO₃ and KClO₃ mixtures. Calculate which salt crystallizes first when cooled from 50°C to 20°C. Plot combined solubility curves. Discuss applications in Lake Magadi and Ngomeni salt works. Solve practice problems.
Class experiment: Test soap lathering with distilled water, tap water, rainwater, and solutions of MgCl₂, NaCl, Ca(NO₃)₂, CaHCO₃, NaHCO₃, ZnSO₄. Record volumes of soap needed. Boil some solutions and retest. Compare results and identify hardness-causing ions.

Calculator, graph paper, data tables, worked examples from textbook
Soap solution, burette, various salt solutions, conical flasks, distilled water, tap water, rainwater, heating source

KLB Secondary Chemistry Form 4, Pages 21-22
KLB Secondary Chemistry Form 4, Pages 22-24

ACIDS, BASES AND SALTS

Types and Causes of Water Hardness

By the end of the lesson, the learner should be able to:
- Define temporary and permanent hardness
-Explain causes of temporary hardness
-Explain causes of permanent hardness
-Write equations for decomposition of hydrogen carbonates

Q/A: Review previous experiment results. Explain temporary hardness caused by Ca(HCO₃)₂ and Mg(HCO₃)₂. Write decomposition equations when boiled. Explain permanent hardness caused by CaSO₄, MgSO₄, Ca(NO₃)₂, Mg(NO₃)₂. Discuss why permanent hardness cannot be removed by boiling.

Student books, examples from previous experiment, chalkboard for equations

KLB Secondary Chemistry Form 4, Pages 24-25

ACIDS, BASES AND SALTS

Effects of Hard Water

By the end of the lesson, the learner should be able to:
- State disadvantages of hard water
-State advantages of hard water
-Explain formation of scum and fur
-Discuss economic and health implications

Discussion based on practical experience: Soap wastage, scum formation on clothes, fur in kettles and pipes, pipe bursting in boilers. Advantages: calcium for bones, protection of lead pipes, use in brewing. Show examples of fur deposits. Calculate economic costs of hard water in households.

Samples of fur deposits, pictures of scaled pipes, calculator for cost analysis

KLB Secondary Chemistry Form 4, Pages 24-25

ACIDS, BASES AND SALTS

Methods of Removing Hardness I
Methods of Removing Hardness II

By the end of the lesson, the learner should be able to:
- Explain removal of hardness by boiling
-Explain removal by distillation
-Write equations for these processes
-Compare effectiveness of different methods

Demonstrate boiling method: Boil hard water samples from previous experiments and test with soap. Write equations for Ca(HCO₃)₂ and Mg(HCO₃)₂ decomposition. Discuss distillation method using apparatus setup. Compare costs and effectiveness. Explain why boiling only removes temporary hardness.

Hard water samples, heating source, soap solution, distillation apparatus diagram
Na₂CO₃ solution, hard water samples, ion exchange resin diagram, Ca(OH)₂, NH₃ solution

KLB Secondary Chemistry Form 4, Pages 25-26