APPLIED SCIENCE UNIT 6: PRINCIPLES AND APPLICATIONS OF CHEMISTRY II

Unit 6: Principles and Applications of Chemistry II Delivery guidance Scientists and laboratory technicians must be able to use and apply key science concepts to work efficiently and effectively in science and science-related organisations. This unit builds on and extends the key science concepts covered in Unit 2: Principles and Applications of Chemistry I. A strong grasp of these concepts will enable learners to use and apply their knowledge and understanding in vocational contexts when studying other units in the specification. Learners will develop an understanding of the importance of energy changes in chemical reactions, how the rate of reaction is governed by different factors and the implications of these factors for the production of chemical substances. Learners will also gain insight into the structure of organic chemicals and their physical and chemical properties. Learners require access to laboratory facilities to carry out practical activities, to investigate the rate of chemical reactions, the concept of equilibrium, the preparation and testing of organic compounds, and the use of chromatography to separate mixtures. If possible, arrange visits to organisations involved in a range of chemical techniques. Approaching the unit This unit includes energetics, rate of reaction and equilibrium, and structures, names, reactions and properties of commercially-important organic compounds. Learners must understand how the physical and chemical properties of substances relate to their uses and methods of production and extraction. For example, knowledge of energetics, and the rate and extent of chemical reactions, is necessary to ensure the correct processes are used safely in the production of chemical substances. Learners will also need a good working knowledge of the structure of organic chemicals and their physical and chemical properties. Learning aim A is primarily concerned with energetics in terms of the energy changes for different types of chemical reaction. A key requirement is for learners to be able to define these types of reaction and apply the correct symbols, units and signs (as applied to exothermic and endothermic). The aim explores the use of reaction profiles to illustrate exothermic and endothermic processes and applies the law of conservation of energy to the calculation of energy changes in chemical systems. For example, learners will use Hess’s law, bond energies and standard enthalpies of combustion to calculate the enthalpy of a reaction. Give learners opportunities to complete safe practical activities which involve measuring temperature changes for different types of reaction (e.g. combustion of hydrocarbons and alcohols, acid–base neutralisations and dissolving compounds). They can use the data obtained to calculate the energy change (using the equation Q = mcpΔT) and, from this, they can calculate the enthalpy change for the reaction. Learning aim B explores how the rate of reaction and equilibrium influence chemical reactions. A key concept is collision theory: chemical reactions are primarily due to the reacting particles colliding with the minimum energy required for a reaction (i.e. activation energy). The aim explores the various factors which can affect the rate of a chemical reaction, including concentration, surface area, temperature and the presence of a catalyst. Learners must carry out practical investigations relating to these factors, using appropriate methods to determine the rate (e.g. change of mass, volume of gas evolved, time taken for a colour change etc.). The results BTEC INTERNATIONAL APPLIED SCIENCE UNIT 6: PRINCIPLES AND APPLICATIONS OF CHEMISTRY II Pearson BTEC International Level 3 Qualifications in Applied Science – Delivery Guide Issue 1 – April 2020 © Pearson Education Limited 2020 2 from these practical investigations (as well as data from other sources) can be used to plot graphs (e.g. volume/time), draw tangents and determine the rate of reaction. Learning aim B also deals with equilibrium. Learners should understand that many chemical reactions can be reversible and that, in a closed system, reactants and products exist in a state of dynamic equilibrium. It explores how the position of equilibrium can be affected by conditions and factors such as concentration, pressure, temperature and the presence of a catalyst. Learners will need to be able to apply the concept of an equilibrium constant (Kc) to determine whether the equilibrium of a system lies to the left or right; they should also be able to write the correct expressions for homogeneous and heterogeneous systems. The latter can be used to calculate Kc for given concentrations of reactants and products and this value can then be used to determine whether the equilibrium lies towards the left or right. Finally, learners should be aware of the importance of equilibrium in determining the efficiency of industrial systems such as the Haber process and Contact process. Learning aim C is concerned with the principles of organic chemistry. Learners should be aware that the tetravalency of carbon can result in strong bonds between carbon atoms and, with hydrogen atoms, can result in chain, branched chain and ring structures. The aim explores the different types of hydrocarbon, including chain, branched chain and ring structures, saturated and unsaturated and those with double and triple bonds. Learners should be able to illustrate the bonding in various hydrocarbons, with reference to σ and ϖ bonding as well as the shapes of molecules, showing the bond angles and symmetry or asymmetry. The aim goes on to look at the properties of organic molecules (alkanes, alkenes, halogenoalkanes and alcohols). There may be some scope for learners to complete relevant practical activities when exploring aspects such as melting/boiling points, solubility, chain length/branching, intermolecular forces, functional groups etc. A key concept in organic chemistry is the homologous series and learners should be able to write the general formula for each series and the molecular and structural formulae for different members of each series. The IUPAC system should be used to name alkanes, alkenes, halogenoalkanes, alcohols, and branched and cyclic compounds. The aim goes on to explore the properties of organic compounds in terms of structural and geometric isomerism. Learning aim D is concerned with the chemical properties of organic compounds, their preparation and separation as well as applications. Alkanes and alkenes are explored in further detail and learners should be aware of the importance of processes such as fractional distillation and cracking for their separation and production. An important reaction of alkanes is combustion, but learners should also be able to describe other reactions such as polymerisation, hydration and various addition reactions (with halogens, hydrogen halides and hydrogen). Learners should generally be able to compare the reactivity of alkanes and alkenes and there is some scope for practical activity here. The aim also explores halogenoalkanes and alcohols. Learners will compare the reactivity of the former in terms of the halogen group, consider the involvement of both halogenoalkanes and alcohols in substitution and elimination reactions, and learn about oxidation of alcohols (primary, secondary and tertiary). Learners should be able to write balanced equations and state the conditions for all reactions studied. They should also be able to construct mechanisms for the reactions. Learners must have the opportunity to prepare organic compounds, applying techniques such as refluxing, distillation, recrystallisation, filtration, drying, MP/BP determination etc. They should understand tests for functional group and be able to calculate percentage yield, identifying reasons for low yield. Learners must know the types of chromatographic technique and be able to explain the principles involved, interpret chromatograms and calculate Rf values. They should also compare BTEC INTERNATIONAL APPLIED SCIENCE UNIT 6: PRINCIPLES AND APPLICATIONS OF CHEMISTRY II Pearson BTEC International Level 3 Qualifications in Applied Science – Delivery Guide Issue 1 – April 2020 © Pearson Education Limited 2020 3 these techniques with other methods of separation and identify situations where they are used to separate and identify components of mixtures. There is some scope for practical activities here. Assessment model Learning aim Key content areas Recommended assessment approach A Understand energy changes in chemical reactions A1 Energetics A report of a practical investigation into endothermic and exothermic reactions, explaining how the different enthalpy changes arise. Calculations to show how enthalpy change for a reaction can be determined by experiment or by using other enthalpy changes. A discussion of the assumptions and sources of error that arise in measurements and calculations of enthalpy change. B Understand how rate and equilibrium influence chemical reactions B1 Rate of reaction B2 Dynamic equilibrium A report of a practical investigation into the factors that affect rate of reaction and analyse gradients from graphs to determine rate. A report investigating the factors that affect equilibrium. Calculations to find Kc or equilibrium concentrations, how to interpret the values and the implications of Kc change with temperature. Explanation of the operational conditions for industrial equilibrium processes to obtain optimum rate and yield of product. C Understand the principles of organic chemistry C1 Structures and naming of organic compounds A report that shows how to determine structures and names for a range of organic compounds, and the differences in bonding between saturated and unsaturated hydrocarbons. Diagrams of structures and bonding will be shown. The report will also provide an explanation and assessment of how functional groups, homologous series, structure and isomerism all characterise and influence physical properties and chemical behaviour. BTEC INTERNATIONAL APPLIED SCIENCE UNIT 6: PRINCIPLES AND APPLICATIONS OF CHEMISTRY II Pearson BTEC International Level 3 Qualifications in Applied Science – Delivery Guide Issue 1 – April 2020 © Pearson Education Limited 2020 4 Learning aim Key content areas Recommended assessment approach D Understand the chemical behaviour, separation and applications of organic compounds D1 Reactions of alkanes and alkenes D2 Reactions of halogenoalkanes and alcohols D3 Organic chemistry mechanisms D4 Preparation and testing of organic compounds D5 Chromatographic techniques A report which reviews the commercially important reactions of hydrocarbons, following the reactions and products from a specific molecule. A comparison of the reactions of alkanes and alkenes and explanation of the main reactions of halogenoalkanes and alcohols. Drawings of mechanisms will complement the comparisons and explanations. Observations and results from the preparation and testing of an organic compound. An explanation of the principles behind the chromatographic separations. Results from the paper chromatography or TLC of an organic compound mixture. Explanations of factors affecting separation and consideration of other separation techniques. An observation report with a checklist, completed by the teacher, including safety. Assessment of different ways to make an organic compound, including factors that would affect the yield and purity. Assessment guidance The unit will be assessed using up to four assignments, one per learning aim. Learners must produce individual evidence that is both original and can be authenticated. For learning aim A, learners must produce a report on investigations into endothermic and exothermic reactions. Learners will: ● measure temperature changes of the solutions or water that absorb or release heat due to the reaction ● calibrate the thermometers used ● accurately measure and record values for temperature, mass and volume ● carry out a risk assessment ● calculate values for enthalpy change for each reaction, using the equation Q = mcpΔT and converting values to kJ mol−1 for comparison ● categorise each reaction as endothermic or exothermic, commenting on the magnitude and sign of the enthalpy change and explaining the underlying processes involved in terms of bond breaking, bond making and reaction profile diagrams BTEC INTERNATIONAL APPLIED SCIENCE UNIT 6: PRINCIPLES AND APPLICATIONS OF CHEMISTRY II Pearson BTEC International Level 3 Qualifications in Applied Science – Delivery Guide Issue 1 – April 2020 © Pearson Education Limited 2020 5 ● calculate a range of standard enthalpy changes for reactions that cannot be determine