Term 1: Rates, equilibrium, pH and energy
The largely qualitative treatment of reaction rates and equilibria encountered in Module 3 is developed within a quantitative and graphical context. This section also allows learners to develop practical quantitative techniques involved in the determination of reaction rates and pH. There are many opportunities for developing mathematical skills, including use of logarithms and exponents, when studying the content of this section and when carrying out quantitative practical work. Students also learn about how Born–Haber cycles are used as a theoretical model to illustrate the energy changes associated with ionic bonding. Entropy and free energy are then introduced as concepts used to predict quantitatively the feasibility of chemical change.
Assessment happens continuously through classwork and homework activities. There is at least one formal assessment each term to monitor progress and assess the content covered in lessons up to the assessment point. Practical activities are embedded within the learning outcomes of the course to ensure achievement of the practical endorsement. Students also assessed in their practical skills through completion of PAGs 10.1 Rates – iodine clock and 11.2- Titration curves
Arrhenius Equation
k = Ae-Ea/RT where k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant and T is the temperature.
Clock Reaction
A reaction in which the time taken for an abrupt visible change to occur is measured. The abrupt change typically indicates the formation of the product.
Colorimetry
A technique used to measure the amount of light absorbed by a solution, used to determine the rate of a reaction.
Rate Constant (k)
A constant value that relates the rate of a reaction at a given temperature to the concentrations of the reactants.
Kc
The equilibrium constant that is equal to the concentration of products raised to their stoichiometric coefficients divided by the concentration of reactants to the power of their stoichiometric coefficients.
Kp
The equilibrium constant that is equal to the partial pressures of the products raised to the power of their stoichiometric coefficients divided by the partial pressures of the reactants raised to the power of their stoichiometric coefficients.
Mole Fraction (XA)
XA = nA /n where XA is the mole fraction of A, nA is the number of moles of A and n is the total number of moles.
Partial Pressure
The pressure that would be exerted by one gas in a mixture if it occupied the container alone. PA = PXA where PA is the partial pressure of A, P is the total pressure and XA is the mole fraction of A.
Acid Dissociation Constant (Ka )
The extent of acid dissociation. pKa = -log(Ka ) and Ka = 10-pKa .
Buffer Solution
A system that minimises pH change on addition of small amounts of an acid or base. A buffer solution can be formed from a weak acid and a salt of the weak acid or from excess weak acid and a strong alkali.
Carbonic Acid-Hydrogencarbonate Buffer
The buffer system present in blood plasma, used to maintain blood pH between 7.35 and 7.45.
Conjugate Acid-Base Pair
A pair of compounds that transform into each other by the transfer of a proton.
End point
The point during a titration when the indicator changes colour. A suitable indicator should change colour near the equivalence point (it should have a pH range within the vertical section of the titration curve).
Equivalence Point
The point during a titration when the amount of acid is exactly equal to the amount of base (full neutralisation occurs). When titrating an acid with a base, [H+ ] is equal to [OH− ] at this point.
Ionic Product of Water (Kw)
The temperature dependent constant that represents the dissociation of water into H+ and OH- .
Titration Curves
A graph which shows the change in pH over the course of a titration.
Vertical Section
The vertical part of a titration curve which contains the equivalence point for the titration. During this section, there is a very large change in pH but a small change in the volume of acid or alkali added.
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Term 2 : Redox, electrode potential, transition elements and aromatic compounds.
In this unit work Module 2 is on redox reactions developed further within this section, including use of volumetric analysis for redox titrations and an introduction of electrochemistry in the context of electrode potentials. This section also provides learners with a deeper knowledge and understanding of the periodic table within the context of the transition elements. It includes the role of ligands in complex ions, stereochemistry, precipitation, ligand substitution and redox reactions. The colour changes and observations in these reactions increase the toolkit of qualitative inorganic tests for identifying unknown ionic compounds. At the end of the term students learn the basics of aromatic compounds (organic chemistry).
Assessment happens continuously through classwork and homework activities. There is at least one formal assessment each term to monitor progress and assess the content covered in lessons up to the assessment point. Practical activities are embedded within the learning outcomes of the course to ensure achievement of the practical endorsement. Students also assessed in their practical skills through completion of PAG 8.2 - Electrochemical cells 2. Students also complete a mock paper on paper 1 (Periodic table, elements and physical chemistry) which included the inorganic part of the course (Modules 2,3 and 5).
Born-Haber Cycle
A cycle which can be used to calculate the lattice enthalpy of an ionic compound using other enthalpy changes.
Enthalpy Change of Atomisation (ΔatH):
The enthalpy change that takes place when one mole of gaseous atoms is formed from an element in its standard state.
Enthalpy Change of Formation (ΔfH)
The enthalpy change that takes place when one mole of a compound is formed from its elements.
First Electron Affinity (ΔeaH)
The amount of energy released when one mole of electrons is added to one mole of gaseous atoms, forming one mole of 1- ions.
First ionisation energy (ΔieH)
The enthalpy change required for the removal of one mole of electrons from one mole of gaseous atoms to form one mole of 1+ ions.
Enthalpy Change of Hydration (ΔhydH)
The enthalpy change that takes place when one mole of gaseous ions are dissolved in water (exothermic)
Enthalpy Change of Solution (ΔsolH)
The enthalpy change that takes place when one mole of solute is dissolved.
Lattice Enthalpy (ΔLEH)
The formation of one mole of an ionic lattice from gaseous ions.
Enthalpy (H)
A value that represents the heat content of a system.
Entropy (S)
A measure of the dispersal of energy in a system. The greater the entropy, the more disordered the system.
Free Energy Change (∆G)
The feasibility of a process depends on entropy change, temperature and enthalpy change
Cell Potential
A measure of the potential difference between two half cells, calculated by combining 2 standard electrode potentials.
Electrochemical Cell
Contains electrodes in an electrolyte and is used to generate current.
E.M.F
Electromotive force, measured in volts.
Fuel Cell
A type of cell that requires a constant supply of fuel and oxygen in order to generate a potential difference.
Redox Titration
A type of titration which involves the reduction of one substance and the oxidation of another.
Standard Electrode (Redox) Potential (Eθ)
The e.m.f. of a half cell compared with a standard hydrogen half cell. This is measured under standard conditions (1 mol dm-3 solution concentrations, 298K and 1 atm).
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Term 3: Aromatic compounds, carbonyls and acids
This section extends the range of functional groups encountered in Module 4. Students learn about aromatic compounds, including the central role of delocalisation within the chemistry of arenes and phenols. Directing groups are also introduced, including their importance to organic synthesis. The important carbonyl compounds, aldehydes and ketones, are then studied. Finally, carboxylic acids and their related functional groups, acyl chlorides and esters, are studied. The importance of acyl chlorides in organic synthesis is emphasised. Furthermore students learn about organic nitrogen compounds, including amines, amides and amino acids. Chirality and optical isomerism is also introduced. Condensation polymerisation is also introduced and compared with addition polymerisation. The importance of carbon–carbon bond formation in organic synthesis is stressed. Learners are also able to taught how to construct multi-stage synthetic routes towards an organic product.
Assessment happens continuously through classwork and homework activities. There is at least one formal assessment each term to monitor progress and assess the content covered in lessons up to the assessment point. Practical activities are embedded within the learning outcomes of the course to ensure achievement of the practical endorsement. There are no set PAGs for this unit, but students will complete practical work to aid understanding.
Bidentate Ligand
A substance that can form 2 dative covalent (coordinate) bonds with a metal ion/ metal. E.g. NH2CH2CH2NH2 (‘en’).
Cis-platin
The cis-isomer of Pt(NH3 )2Cl2 , used as an anticancer drug. Cis-platin binds to DNA, preventing cell replication.
Complex Ion
An ion which has a central metal atom (typically a transition element) surrounded by ligands. The ligands are bound to the transition metal centre by dative coordinate bonds.
Coordination Number
The number of dative covalent bonds formed between ligands and a metal ion centre.
Ligand Substitution
A reaction in which one ligand in a transition metal complex is replaced by another. Typically, these reactions are associated with a colour change
Monodentate Ligand
A substance that can form 1 dative covalent (coordinate) bond with a metal ion/ metal. E.g. H2O, Cl- and NH3 .
Octahedral
The shape of a transition metal complex with a coordination number 6. E.g. [Cu(H2O)6 ] 2+ .
Optical Isomers
Compounds that have the same structural formulae but are mirror images of one another. Optical isomerism occurs in [Ni(en)3 ] 2+ .
Square Planar
One of the possible shapes of a transition metal complex with a coordination number of 4. E.g., Pt(NH3 )2Cll.
Tetrahedral
One of the possible shapes of a transition metal complex with a coordination number of 4. E.g. CuCl4 2-
Transition Elements
d-block elements that can form an ion with an incomplete d-subshell. Transition elements have more than one oxidation state, form coloured ions and can act as catalysts.
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Term 4: Core and advanced organic chemistry
In this unit students revisit and consolidate their knowledge on core (module 4) and advanced organic chemistry (module 6). The instrumentation methods of analysis studied during the A level course provide learners with an important base of knowledge, understanding and awareness for further study in Higher Education and in many areas of employment in the broad scientific field. This section also looks at how unknown organic
functional groups can be analysed and identified using simple test-tube tests.
Assessment happens continuously through classwork and homework activities. There is at least one formal assessment each term to monitor progress and assess the content covered in lessons up to the assessment point. Practical activities are embedded within the learning outcomes of the course to ensure achievement of the practical endorsement. Students also assessed in their practical skills through completion of PAGs 6.1 - synthesis of aspirin and 12.1 Investigating iron tablets. Students also complete a mock exam on paper 2, Synthesis and
analytical techniques (modules 1,2,4 and 6)
Aromatic Compound
A compound containing at least one benzene ring.
Electron Donating Groups
Groups which donate electrons into the aromatic ring when they are attached to a carbon in the ring. O
Electron Withdrawing Groups
Groups which pull electron density away from the delocalised π system of benzene. N
Halogen Carrier
A Lewis acid that can bind to a halogen molecule, weakening the halogen bond and allowing the halogen to function as an electrophile and attack electrons in an aromatic ring.
Kekulé’s Structure of Benzene
A model of benzene which contains alternating C=C double and C-C single bonds in a hexagonal ring, with each carbon atom bound to one hydrogen atom.
Phenol
A weak acid that reacts with NaOH but not carbonates. Phenol has an aromatic ring with an OH group attached
Tollens’ Reagent
Also known as ammoniacal silver nitrate, this reagent forms a silver mirror in the presence of an aldehyde and can be used to distinguish between aldehydes and ketones
Acyl Chloride
A compound containing the functional group -C(Cl)=O
Ester
A compound containing the R-COO-R’ functional group (where R and R’ are alkyl groups).
2,4-dinitrophenylhydrazine
Also known as Brady’s reagent, this compound forms an orange precipitate in the presence of aldehydes and ketones
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Term 5: Revision - Unified chemistry
In this unit students, having completed all modules (1-6), focus on revision and making links with the different units of the specification preparing themselves for the third paper - Unified chemistry which is worth 70 marks and includes on a variety of questions (e.g. short answer, structured
questions, problem solving, calculations, practical, and extended response questions) from both the inorganic and organic parts of the course.
Assessment happens continuously through classwork and homework activities. There is at least one formal assessment each term to monitor progress and assess the content covered in lessons up to the assessment point. Practical activities are embedded within the learning outcomes of the course to ensure achievement of the practical endorsement. There are no set PAGs for this unit, but students will complete practical work to aid understanding.
Amines
Compounds that contain the NR3 functional group (where R could be hydrogen atoms or alkyl chains)
α-Amino Acid
A compound with the general formula RCH(NH2 )COOH, where an amino group and a carboxylic acid group are bonded to the same carbon atom.
Chiral Centre
A carbon atom which is bonded to 4 different groups.
Addition Polymerisation
The formation of a long chain molecule when many monomers join together (the polymer is the only product).
Amide Hydrolysis
Amides can either be hydrolysed under acidic conditions (forming carboxylic acids and ammonium salts) or under alkaline conditions (forming carboxylate salts and either ammonia or an amine).
Condensation Polymerisation
A long chain molecule formed when monomers react together with the release of small molecules such as water
Ester Hydrolysis
Esters can either be hydrolysed with hot aqueous acid (forming carboxylic acids and alcohols) or with hot aqueous alkali (forming carboxylate salts and alcohols).
Nucleophilic Substitution
A reaction in which an electron pair donor attacks an electrophilic atom (an atom with a partial or full positive charge) to replace an atom/ group of atoms.
Nitrile
An organic compound which contains a -C≡N group bound to an alkyl chain.
Nucleophilic Substitution
A reaction in which an electron pair donor attacks an electrophilic atom (an atom with a partial or full positive charge) to replace an atom/ group of atoms.
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Term 6: Exams
Students sit exams on papers 1,2 and 3.
Students sit exams on papers 1,2 and 3.
Gas Chromatography
A type of chromatography in which a column is packed with a solid (or a solid coated in a liquid) and a gas is passed through the column under pressure at high temperature.
Mobile Phase
A substance that moves through the chromatography system to separate the mixture. This may be a gas (GC) or a liquid (TLC).
Qualitative Analysis
Techniques that are used to identify whether or not an element, functional group or ion is present in a sample.
Retention Time
The time taken for a sample to travel from the inlet to the detector in GC. The recorded retention time can be compared with standards to identify the substances in the mixture.
Rf value
In TLC, the Rf values can be calculated as shown below then compared with standards to identify what substances present in a mixture. Rf = distance moved by substance ÷ distance moved by solvent
Stationary Phase
Asubstance through which the mobile phase moves in chromatography. This is typically a solid although a solid coated in a liquid may be used in GC.
Thin Layer Chromatography (TLC)
Thin Layer Chromatography (TLC): a type of chromatography in which a plate is coated with a solid and a solvent moves up the plate.
Carbon-13 NMR Spectroscopy
A type of NMR spectroscopy which analyses 13C nuclei.
Chemical Shift
The shift of a carbon or proton environment relative to standard (TMS). The chemical shift value (δ) depends on the molecular environment of the proton/ carbon atom.
Coupling
Interaction between adjacent non-equivalent protons during NMR spectroscopy.
D2O Exchange
As O-H and N-H peaks can appear across a wide range of chemical shift values on a proton NMR spectrum, D2O exchange can be used to identify which peaks are caused by O-H and N-H protons
Deuterated Solvent
A solvent, such as CDCl3 , in which all of the hydrogen atoms have been replaced by deuterium (2H).
Doublet
A signal on a 1H NMR spectra made up of 2 peaks, indicating that there is 1 adjacent non-equivalent proton.
Elemental Analysis
A sample is analysed to determine the proportion of elements that make up the compound present
Environment
In NMR spectroscopy, a proton or carbon environment considers the atoms/ groups that are adjacent to that hydrogen/ carbon atom
IR Spectroscopy
A technique used to identify particular bonds and functional groups within a molecule.
Mass Spectroscopy
A technique used to identify compounds and determine relative molecular mass by measuring their mass to charge ratio.
Nuclear Magnetic Resonance (NMR)
A technique that uses the absorption of electromagnetic radiation by a nucleus in an external magnetic field to analyse the structure of a compound. T
Proton NMR Spectroscopy
A type of NMR spectroscopy which analyses 1H nuclei. The number of peaks on the spectrum shows the number of proton environments and the chemical shifts show the type of environments.
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