Subject content

Unit 1: Foundation Chemistry

Introduction

Introduction 

This unit explores the fundamental principles that form the basis of Chemistry. Wherever possible, candidates should carry out experimental work to illustrate the theoretical principles included in this unit.

The development of these skills is associated with the Investigative and Practical Skills detailed in Unit 3.

Candidates should

Atomic Structure

Atomic Structure

Fundamental Particles

  • be able to describe the properties of protons, neutrons and electrons in terms of relative charge and relative mass
  • know that early models of atomic structure predicted that atoms and ions with noble gas electron arrangements should be stable

Protons, neutrons and electrons

  • understand the importance of these particles in the structure of the atom and appreciate that there are various models to illustrate atomic structure

Mass number and isotopes

  • be able to recall the meaning of mass number (A) and atomic (proton) number (Z)
  • be able to explain the existence of isotopes
  • understand the principles of a simple mass spectrometer, limited to ionisation, acceleration, deflection and detection
  • know that the mass spectrometer gives accurate information about relative isotopic mass and also about the relative abundance of isotopes
  • be able to interpret simple mass spectra of elements and calculate relative atomic mass from isotopic abundance, limited to mononuclear ions
  • know that mass spectrometry can be used to identify elements (as used for example in planetary space probes)
  • know that mass spectrometry can be used to determine relative molecular mass

Electron arrangement

  • know the electron configurations of atoms and ions up to Z = 36 in terms of levels and sub-levels (orbitals) s, p and d
  • know the meaning of the term ionisation energy.
  • understand how ionisation energies in Period 3 (Na – Ar) and in Group 2 (Be – Ba) give evidence for electron arrangement in sub-levels and in levels

Amount of Substance

Amount of Substance

Relative atomic mass and relative molecular mass

  • be able to define relative atomic mass (Ar) and relative molecular mass (Mr) in terms of 12C. (The term relative formula mass will be used for ionic compounds)

The mole and the Avogadro constant (L)

  • understand the concept of a mole as applied to electrons, atoms, molecules, ions, formulae and equations
  • understand the concept of the Avogadro constant. (Calculation not required)

The ideal gas equation

  • be able to recall the ideal gas equation pV = nRT and be able to apply it to simple calculations in S.I. units, for ideal gases

Empirical and molecular formulae

  • understand the concept of, and the relationship between, empirical and molecular formulae
  • be able to calculate empirical formulae from data giving percentage composition by mass

Balanced equations and associated calculations

  • be able to write balanced equations (full and ionic) for reactions studied
  • be able to balance equations for unfamiliar reactions when reactants and products are specified. (This is an important skill that applies in all units.)
  • be able to calculate reacting volumes of gases
  • be able to calculate concentrations and volumes for reactions in solutions, limited to titrations of monoprotic acids and bases and examples for which the equations are given
  • know that %

  • be able to calculate reacting masses, % yields and % atom economies from balanced equations

Bonding

Bonding

Nature of ionic, covalent and metallic bonds

  • understand that ionic bonding involves attraction between oppositely charged ions in a lattice
  • know that a covalent bond involves a shared pair of electrons
  • know that co-ordinate bonding is dative covalency
  • understand that metallic bonding involves a lattice of positive ions surrounded by delocalised electrons

Bond polarity

  • understand that electronegativity is the power of an atom to withdraw electron density from a covalent bond
  • understand that the electron distribution in a covalent bond may not be symmetrical
  • know that covalent bonds between different elements will be polar to different extents

Forces acting between molecules

  • understand qualitatively how molecules may interact by permanent dipole–dipole, induced dipole–dipole (van der Waals') forces and hydrogen bonding
  • understand the importance of hydrogen bonding in determining the boiling points of compounds and the structures of some solids (e.g. ice)

States of matter

  • be able to explain the energy changes associated with changes of state
  • recognise the four types of crystal: ionic, metallic, giant covalent (macromolecular) and molecular
  • know the structures of the following crystals: sodium chloride, magnesium, diamond, graphite, iodine and ice
  • be able to relate the physical properties of materials to the type of structure and bonding present

Shapes of simple molecules and ions

  • understand the concept of bonding and lone (non bonding) pairs of electrons as charge clouds.
  • be able, in terms of electron pair repulsion, to predict the shapes of, and bond angles in, simple molecules and ions, limited to 2, 3, 4, 5 and 6 co-ordination
  • know that lone pair/lone pair repulsion is greater than lone pair/bonding pair repulsion, which is greater than bonding pair/bonding pair repulsion, and understand the resulting effect on bond angles

Periodicity

Periodicity

Classification of elements in s, p and d blocks

  • be able to classify an element as s, p or d block according to its position in the Periodic Table

Properties of the elements of Period 3 to illustrate periodic trends

  • be able to describe the trends in atomic radius, first ionisation energy, melting and boiling points of the elements Na – Ar
  • understand the reasons for the trends in these properties

Introduction to Organic Chemistry

Introduction to Organic Chemistry

Nomenclature

  • know and understand the terms empirical formula, molecular formula, structural formula, displayed formula, homologous series and functional group
  • be able to apply IUPAC rules for nomenclature to simple organic compounds, limited to chains with up to 6 carbon atoms limited in this module to alkanes, alkenes and haloalkanes

Isomerism

  • know and understand the meaning of the term structural isomerism
  • be able to draw the structures of chain, position and functional group isomers

Alkanes

Alkanes

Fractional distillation of crude oil

  • know that alkanes are saturated hydrocarbons
  • know that petroleum is a mixture consisting mainly of alkane hydrocarbons
  • understand that different components (fractions) of this mixture can be drawn off at different levels in a fractionating column because of the temperature gradient

Modification of alkanes by cracking

  • understand that cracking involves the breaking of C–C bonds in alkanes
  • know that thermal cracking takes place at high pressure and high temperature and produces a high percentage of alkenes (mechanism not required)
  • know that catalytic cracking takes place at a slight pressure, high temperature and in the presence of a zeolite catalyst and is used mainly to produce motor fuels and aromatic hydrocarbons (mechanism not required)
  • understand the economic reasons for the cracking of alkanes (e.g. ethene used for poly(ethene); conversion of heavy fractions into higher value products)

Combustion of alkanes

  • know that alkanes are used as fuels and understand that their combustion can be complete or incomplete and that the internal combustion engine produces a number of pollutants (e.g. NOx, CO and unburned hydrocarbons)
  • know that these pollutants can be removed using catalytic converters
  • know that combustion of hydrocarbons containing sulfur leads to sulfur dioxide that causes air pollution and understand how sulfur dioxide can be removed from flue gases using calcium oxide
  • know that the combustion of fossil fuels (including alkanes) results in the release of carbon dioxide into the atmosphere
  • know that carbon dioxide, methane and water vapour are referred to as greenhouse gases and that these gases may contribute to global warming

Unit 2 - Chemistry in Action

Introduction

Introduction

This unit introduces more of the principles that underpin chemistry and looks at the applications of these principles and those that have been developed in Unit 1.


Wherever possible, candidates should carry out experimental work to illustrate the theoretical principles included in this unit.

A knowledge of the Chemistry in Unit 1 is assumed in this unit.

Candidates should

Energetics

Energetics

Enthalpy change (ΔH)

  • know that reactions can be endothermic or exothermic
  • understand that enthalpy change ( ) is the heat energy change measured under conditions of constant pressure
  • know that standard enthalpy changes refer to standard conditions, i.e. 100 kPa and a stated temperature (e.g. )
  • be able to recall the definition of standard enthalpies of combustion ( ) and formation ( )

Calorimetry

  • be able to calculate the enthalpy change from the heat change in a reaction using the equation

Simple applications of Hess's Law

  • know Hess's Law and be able to use it to perform simple calculations, for example calculating enthalpy changes for reactions from enthalpies of combustion or enthalpies of formation

Bond enthalpies

  • be able to determine mean bond enthalpies from given data
  • be able to use mean bond enthalpies to calculate a value of for simple reactions

Kinetics

Kinetics

Collision theory

  • understand that reactions can only occur when collisions take place between particles having sufficient energy
  • be able to define the term activation energy and understand its significance
  • understand that most collisions do not lead to reaction

Maxwell–Boltzmann distribution

  • have a qualitative understanding of the Maxwell–Boltzmann distribution of molecular energies in gases
  • be able to draw and interpret distribution curves for different temperatures

Effect of temperature on reaction rate

  • understand the qualitative effect of temperature changes on the rate of reaction
  • understand how small temperature increases can lead to a large increase in rate

Effect of concentration

  • understand the qualitative effect of changes in concentration on rate of reaction

Catalysts

  • know the meaning of the term catalyst
  • understand that catalysts work by providing an alternative reaction route of lower activation energy

Equilibria

Equilibria

The dynamic nature of equilibria

  • know that many chemical reactions are reversible
  • understand that for a reaction in equilibrium, although the concentrations of reactants and products remain constant, both forward and reverse reactions are still proceeding at equal rates

Qualitative effects of changes of pressure, temperature and concentration on a system in equilibrium

  •  be able to use Le Chatelier's principle to predict the effects of changes in temperature, pressure and concentration on the position of equilibrium in homogeneous reactions
  • know that a catalyst does not affect the position of equilibrium

Importance of equilibria in industrial processes

  • be able to apply these concepts to given chemical processes
  • be able to predict qualitatively the effect of temperature on the position of equilibrium from the sign of for the forward reaction
  • understand why a compromise temperature and pressure may be used
  • know about the hydration of ethene to form ethanol and the reaction of carbon monoxide with hydrogen to form methanol as important industrial examples where these principles can be applied
  • know the importance of these alcohols as liquid fuels

Redox Reactions

Redox Reactions

Oxidation and reduction

  • know that oxidation is the process of electron loss
  • know that oxidising agents are electron acceptors
  • know that reduction is the process of electron gain
  • know that reducing agents are electron donors

Oxidation states

  • know and be able to apply the rules for assigning oxidation states in order to work out the oxidation state of an element in a compound from its formula
  • understand oxidation and reduction reactions of s and p block elements

Redox equations

  • be able to write half-equations identifying the oxidation and reduction processes in redox reactions when the reactants and products are specified
  • be able to combine half-equations to give an overall redox equation

Group 7(17), the Halogens

Group 7(17), the Halogens

Trends in physical properties

  • understand the trends in electronegativity and boiling point of the halogens

Trends in the oxidising abilities of the halogens

  • understand that the ability of the halogens (from fluorine to iodine) to oxidise decreases down the group (e.g. the displacement reactions with halide ions in aqueous solution)

Trends in the reducing abilities of the halide ions

  • understand the trend in reducing ability of the halide ions
  • know the different products formed by reaction of NaX and

Identification of halide ions using silver nitrate

  • understand why acidified silver nitrate solution is used as a reagent to identify and distinguish between

  • know the trend in solubility of the silver halides in ammonia

  • Uses of chlorine and chlorate(I)

    • know the reactions of chlorine with water and the use of chlorine in water treatment
    • appreciate that the benefits to health of water treatment by chlorine outweigh its toxic effects
    • know the reaction of chlorine with cold, dilute, aqueous NaOH and the uses of the solutions formed

Group 2, the Alkaline Earth Metals

Group 2, the Alkaline Earth Metals

Trends in physical properties

  • understand the trends in atomic radius, first ionisation energy and melting point of the elements Mg – Ba

Trends in chemical properties

  • know the reactions of the elements Mg – Ba with water and recognise the trend
  • know the relative solubilities of the hydroxides of the elements Mg – Ba and that is sparingly soluble
  • know the use of in medicine and of in agriculture
  • know the relative solubilities of the sulfates of the elements Mg – Ba
  • understand why acidified solution is used as a reagent to test for sulfate ions
  • know the use of in medicine

Extraction of Metals

Extraction of Metals

Principles of metal extraction

  • know that metals are found in ores, usually as oxides or sulfides and that sulfide ores are usually converted into oxides by roasting in air
  • understand the environmental problems associated with the conversion of sulfides into oxides and also that the sulfur dioxide produced can be used to manufacture sulfuric acid
  • understand that extraction of metals involves reduction
  • understand that carbon and carbon monoxide are cheap and effective reducing agents that are used in the extraction of iron, manganese and copper (reduction equations and conditions only)
  • know why carbon reduction is not used for extraction of titanium, aluminium and tungsten
  • understand how aluminium is manufactured from purified bauxite (energy considerations, electrode equations and conditions only)
  • understand how titanium is extracted from via (equations and conditions only: either Na or Mg as a reducing agent)
  • understand how tungsten is extracted from by reduction with hydrogen (equation, conditions and risks only)

Environmental aspects of metal extraction

  • understand the environmental and economic advantages and disadvantages of recycling scrap metals compared with the extraction of metals
  • understand the environmental advantages of using scrap iron to extract copper from aqueous solutions compared with the high-temperature carbon reduction of copper oxide
  • know that the usual source of such aqueous solutions is low grade ore

Haloalkanes

Haloalkanes

Synthesis of chloroalkanes

  • understand the reaction mechanism of methane with chlorine as a free-radical substitution reaction in terms of initiation, propagation and termination steps
  • know that chloroalkanes and chlorofluoroalkanes can be used as solvents
  • understand that ozone, formed naturally in the upper atmosphere is beneficial
  • be able to use equations such as the following to explain why chlorine atoms catalyse the decomposition of ozone and contribute to the formation of a hole in the ozone layer
  • know that chlorine atoms are formed in the upper atmosphere when energy from ultra-violet radiation causes C–Cl bonds in chlorofluorocarbons (CFCs) to break
  • appreciate that legislation to ban the use of CFCs was supported by chemists and that they have now developed alternative chlorine-free compounds 

Nucleophilic substitution

  • understand that haloalkanes contain polar bonds
  • understand that haloalkanes are susceptible to nucleophilic attack, limited to , and
  • understand the mechanism of nucleophilic substitution in primary haloalkanes
  • understand that the carbon–halogen bond enthalpy influences the rate of hydrolysis
  • appreciate the usefulness of these reactions in organic synthesis

Elimination

  • understand concurrent substitution and elimination (including mechanisms) in the reaction of a haloalkane (e.g. 2- bromopropane with potassium hydroxide) and the role of the reagent as both nucleophile and base
  • appreciate the usefulness of this reaction in organic synthesis

Alkenes

Alkenes

Alkenes: structure, bonding and reactivity

  • know that alkenes are unsaturated hydrocarbons
  • know that bonding in alkenes involves a double covalent bond
  • know that the arrangement >C=C< is planar
  • know that the alkenes can exhibit E-Z stereoisomerism
  • be able to draw the structures of E and Z isomers
  • understand that E-Z isomers exist due to restricted rotation about the C=C bond
  • understand that the double bond in an alkene is a centre of high electron density

Addition reactions of alkenes

  • understand the mechanism of electrophilic addition of alkenes with
  • know that bromine can be used to test for unsaturation
  • be able to predict the products of addition to unsymmetrical alkenes by reference to the relative stabilities of primary, secondary and tertiary carbocation intermediates
  • understand that alcohols are produced industrially by hydration of alkenes in the presence of an acid catalyst.
  • know the typical conditions for the industrial production of ethanol from ethene

Polymerisation of alkenes

  • know how addition polymers are formed from alkenes
  • recognise that poly(alkenes) like alkanes are unreactive
  • be able to recognise the repeating unit in a poly(alkene)
  • know some typical uses of poly(ethene) and poly(propene) and know that poly(propene) is recycled

Alcohols

Alcohols

Nomenclature

  • be able to apply IUPAC rules for nomenclature to alcohols, aldehydes, ketones and carboxylic acids limited to chains with up to 6 carbon atoms

Ethanol production

  • know how ethanol is produced industrially by fermentation
  • know the conditions for this reaction and understand the economic and environmental advantages and disadvantages of this process compared with the industrial production from ethene
  • understand the meaning of the term biofuel
  • know that the term carbon neutral refers to 'an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere'
  • appreciate the extent to which ethanol, produced by fermentation, can be considered to be a carbon-neutral biofuel

Classification and reactions

  • understand that alcohols can be classified as primary, secondary or tertiary
  • understand that tertiary alcohols are not easily oxidised
  • understand that primary alcohols can be oxidised to aldehydes and carboxylic acids and that secondary alcohols can be oxidised to ketones by a suitable oxidising agent such as acidified potassium dichromate(VI) (equations showing [O] as oxidant are acceptable)
  • be able to use a simple chemical test to distinguish between aldehydes and ketones (e.g. Fehling's solution or Tollens' reagent)

Elimination

  • know that alkenes can be formed from alcohols by acid catalysed elimination reactions (mechanism not required)
  • appreciate that this method provides a possible route to polymers without using monomers derived from oil

Analytical Techniques

Analytical Techniques

Mass spectrometry

  • understand that high resolution mass spectrometry can be used to determine the molecular formula of a compound from the accurate mass of the molecular ion

Infrared spectroscopy

  • understand that certain groups in a molecule absorb infrared radiation at characteristic frequencies
  • understand that 'fingerprinting' allows identification of a molecule by comparison of spectra
  • be able to use spectra to identify particular functional groups and to identify impurities, limited to data presented in wavenumber form
  • understand the link between absorption of infrared radiation by bonds in , methane and water vapour and global warming

Unit 3 - Investigative and Practical Skills in AS Chemistry

Investigative and practical skills in AS Chemistry

Investigative and practical skills in AS Chemistry

Candidates should carry out experimental and investigative activities in order to develop their practical skills. Experimental and investigative activities should be set in contexts appropriate to, and reflect the demand of, the AS content. These activities should allow candidates to use their knowledge and understanding of Chemistry in planning, carrying out, analysing and evaluating their work.

The content of Units 1 and 2 provides a basis for different practical topics which may be used for experimental and investigative skills. The experience of dealing with such activities will develop the skills required for the assessment of these skills in the Unit. Examples of suitable experiments that could be considered throughout the course will be provided in the Teaching and learning resources web pages.

It is expected that candidates will be able to use and be familiar with 'standard' laboratory equipment which is deemed suitable at AS level, throughout their experiences of carrying out their practical activities.

The skills developed in the course of their practical activities are elaborated further in the How Science Works section of this specification (see Section 3.7).

In the course of their experimental work, candidates should learn to

  • demonstrate and describe ethical, safe and skilful practical techniques
  • process and select appropriate qualitative and quantitative methods
  • make, record and communicate reliable and valid observations
  • make measurements with appropriate precision and accuracy
  • analyse, interpret, explain and evaluate the methodology, results and impact of their own and others' experimental and investigative activities in a variety of ways.

The Centre-Assessed Option, Route T

The practical and investigative skills will be centre assessed through

  • Investigative Skills Assignment (ISA)
  • Practical Skills Assessment (PSA).

The ISA will require candidates to undertake practical work, collect and process data and use it to answer questions in a written test (ISA test) (see Section 3.8).

The PSA requires centre assessment, throughout the AS course, of the candidate's ability to follow and undertake certain standard practical activities across the three areas of Chemistry: Inorganic, Organic and Physical. These practical activities are listed on the next page.

The Externally Marked Option, Route X

The practical and investigative skills will be externally assessed by AQA through

  • Practical Skills Verification (PSV) and
  • Externally Marked Practical Assignment (EMPA)

The PSV will require candidates to undertake the practical activities identified on the next page, in order to gain experience of a wide range of practical skills. These activities must allow a candidate suitable opportunity to demonstrate safe and skilful practice, as well as producing reliable and valid observations. AQA will require teacher verification, by means of a tick box on the front cover of the EMPA written test, that a candidate is experienced in these skills.

The EMPA, in a similar way to the ISA, will require candidates to undertake practical work, collect and process data and use it to answer questions in a written test (EMPA test) (see Section 3.8).

Practical Skills Assessment

The PSA is designed to credit candidates for the practical work they undertake naturally as part of the course.Further information is provided in Section 3.8, but it is expected that candidates will complete at least two practical activities from each of the three areas of Chemistry listed below.

AS Inorganic Chemistry
Task Possible Context
Make up a volumetric solution The preparation of a standard solution of sodium carbonate
Carry out a simple acid-base titration Determine the concentration of unknown hydrochloric acid by titration
Carry out some inorganic tests Tests for anions
AS Physical Chemistry
Task Possible Context
Measure an enthalpy change Use Hess's law to find an unknown enthalpy change, such as the reaction of anhydrous copper(II) sulfate with water to produce hydrated crystals
Determine the Mr of a volatile liquid or the Mr of a gas Determine the Mr of hexane or the Mr of carbon dioxide
Investigate how the rate of a reaction changes with temperature. Investigate the rate of reaction of sodium thiosulfate with acid at different temperatures
AS Organic Chemistry
Task Possible Context
Distil a product from a reaction The preparation of ethanal from the oxidation of ethanol or the preparation of cyclohexene from the dehydration of cyclohexanol
Carry out some organic tests Tests for alkene, alcohol, acid, aldehyde
Investigate the combustion of alcohols Use a calorimetric method to measure the enthalpies of combustion in an homologous series of alcohols

Unit 4 - Kinetics, Equilibria and Organic Chemistry

Introduction

Introduction

This unit develops the concepts of physical chemistry introduced at AS. Kinetics and equilibria are both treated quantitatively. Acids, bases and buffer solutions and the changes in pH during titrations are considered.

The study of organic chemistry is extended to include compounds containing the carbonyl group, aromatic compounds, amines, amino acids and polymers. The final section examines the way in which spectroscopic techniques are used to determine the molecular formulae and structures of organic compounds. The emphasis is on problem solving rather than on spectroscopic theory.

Candidates should

Kinetics

Kinetics

Simple rate equations

  • understand and be able to use rate equations of the form where m and n are the orders of reaction with respect to reactants A and B (m, n restricted to values 1, 2 or 0)

Determination of rate equation

  • be able to derive the rate equation for a reaction from data relating initial rate to the concentrations of the different reactants
  • be able to explain the qualitative effect of changes in temperature on the rate constant k
  • understand that the orders of reactions with respect to reactants can be used to provide information about the rate determining/limiting step of a reaction

Equilibria

Equilibria

Equilibrium constant Kc for homogeneous systems

  • know that Kc is the equilibrium constant calculated from equilibrium concentrations for a system at constant temperature
  • be able to construct an expression for Kc for an homogeneous system in equilibrium;
  • be able to perform calculations involving such an expression

Qualitative effects of changes of temperature and concentration

  • be able to predict the effects of changes of temperature on the value of the equilibrium constant
  • understand that the value of the equilibrium constant is not affected by changes either in concentration or the addition of a catalyst

Acids and Bases

Acids and Bases

Brønsted–Lowry acid–base equilibria in aqueous solution

Candidates should

  • know that an acid is a proton donor
  • know that a base is a proton acceptor
  • know that acid–base equilibria involve the transfer of protons

Definition and determination of pH

Candidates should

  • know that pH = – log10[H+], where [ ] represents the concentration in mol dm–3
  • be able to convert concentration into pH and vice versa
  • be able to calculate the pH of a solution of a strong acid from its concentration

The ionic product of water, Kw

Candidates should

  • know that water is weakly dissociated
  • know that Kw = [H+][OH ]
  • be able to calculate the pH of a strong base from its concentration.

Weak acids and bases Ka for weak acids

Candidates should

  • know that weak acids and weak bases dissociate only slightly in aqueous solution
  • be able to construct an expression, with units, for the dissociation constant Ka for a weak acid
  • know that pKa = – log10 Ka
  • be able to perform calculations relating the pH of a weak acid to the dissociation constant, Ka, and the concentration

pH curves, titrations and indicators

Candidates should

  • understand the typical shape of pH curves for acid–base titrations in all combinations of weak and strong monoprotic acids and bases
  • be able to use pH curves to select an appropriate indicator
  • be able to perform calculations for the titrations of monoprotic and diprotic acids with sodium hydroxide, based on experimental results

Buffer action

Candidates should

  • be able to explain qualitatively the action of acidic and basic buffers
  • know some applications of buffer solutions
  • be able to calculate the pH of acidic buffer solutions

Nomenclature and Isomerism in Organic Chemistry

Nomenclature and Isomerism in Organic Chemistry

Naming organic compounds

Candidates should

  •  be able to apply IUPAC rules for nomenclature not only to the simple organic compounds, limited to chains with up to 6 carbon atoms, met at AS, but also to benzene and the functional groups listed in this unit

Isomerism

Candidates should

  • know and understand the meaning of the term structural isomerism
  • know that E-Z isomerism and optical isomerism are forms of stereoisomerism
  • know that an asymmetric carbon atom is chiral and gives rise to optical isomers which exist as non super-imposable mirror images and differ only in their effect on plane polarised light
  • understand the meaning of the terms enantiomer and racemate
  • understand why racemates are formed
  • be able to draw the structural formulae and displayed formulae of isomers
  • Appreciate that drug action may be determined by the stereochemistry of the molecule and that different optical isomers may have very different effects

Compounds Containing the Carbonyl Group

Compounds Containing the Carbonyl Group

Aldehydes and ketones

Candidates should

  • know that aldehydes are readily oxidised to carboxylic acids and that this forms the basis of a simple chemical test to distinguish between aldehydes and ketones (e.g. Fehling's solution and Tollens' reagent)
  • appreciate the hazards of synthesis using HCN/KCN
  • know that aldehydes can be reduced to primary alcohols and ketones to secondary alcohols using reducing agents such as NaBH4. Mechanisms showing H are required (equations showing [H] as reductant are acceptable)
  • understand the mechanism of the reaction of carbonyl compounds with HCN as a further example of nucleophilic addition producing hydroxynitriles

Carboxylic acids and esters

Candidates should

  •  know that carboxylic acids are weak acids but will liberate CO2 from carbonates
  • know that carboxylic acids and alcohols react, in the presence of a strong acid catalyst, to give esters
  • know that esters can have pleasant smells
  • know the common uses of esters (e.g. in solvents, plasticizers, perfumes and food flavourings)
  • know that vegetable oils and animal fats are esters of propane-1,2,3-triol (glycerol)
  • know that esters can be hydrolysed
  • understand that vegetable oils and animal fats can be hydrolysed to give soap, glycerol and long chain carboxylic (fatty) acids
  • know that biodiesel is a mixture of methyl esters of long chain carboxylic acids

Acylation

Candidates should

  • know that vegetable oils can be converted into biodiesel by reaction with methanol in the presence of a catalyst
  • know the reaction with ammonia and primary amines with acyl chlorides and acid anhydrides
  • know the reactions of water, alcohols, ammonia and primary amines with acyl chlorides and acid anhydrides
  • understand the mechanism of nucleophilic addition– elimination reactions between water, alcohols, ammonia and primary amines with acyl chlorides
  • understand the industrial advantages of ethanoic anhydride over ethanoyl chloride in the manufacture of the drug aspirin

Aromatic Chemistry

Aromatic Chemistry

Bonding

Candidates should

  • understand the nature of the bonding in a benzene ring, limited to planar structure and bond length intermediate between single and double

Delocalisation stability

Candidates should

  • understand that delocalisation confers stability to the molecule
  • be able to use thermochemical evidence from enthalpies of hydrogenation to illustrate this principle

Electrophilic substitution

Candidates should

  • understand that electrophilic attack in arenes results in substitution; mechanisms limited to the monosubstitutions given below

Nitration

Candidates should

  • understand that nitration is an important step in synthesis e.g. manufacture of explosives and formation of amines from which dyestuffs are manufactured
  • understand the mechanism of nitration, including the generation of the nitronium ion

Friedel–Crafts acylation reactions

Candidates should

  • understand that Friedel–Crafts acylation reactions are important steps in synthesis
  • understand the mechanism of acylation using AlCl3 as catalyst

Amines

Amines

Base properties (Brønsted–Lowry)

Candidates should

  • be able to explain the difference in base strength between ammonia, primary aliphatic and primary aromatic amines in terms of the availability of a lone pair on the N atom

Nucleophilic properties

Candidates should

  • understand that the nucleophilic substitution reactions (including mechanism) of ammonia and amines with haloalkanes form primary, secondary, tertiary amines and quaternary ammonium salts; know that the latter can be used as cationic surfactants

Preparation

Candidates should

  • know that primary aliphatic amines can be prepared from haloalkanes and by the reduction of nitriles
  • know that aromatic amines are prepared by the reduction of nitro compounds

Amino

Amino Acids

Acid and base properties

Candidates should

  • understand that amino acids have both acidic and basic properties, including the formation of zwitterions

Proteins

Candidates should

  • understand that proteins are sequences of amino acids joined by peptide links
  • understand that hydrolysis of the peptide link produces the constituent amino acids
  • know that mixtures of amino acids can be separated by chromotography
  • understand the importance of hydrogen bonding in proteins (detailed structures not required)

Polymers

Polymers

Addition polymers

  • be able to draw the repeating unit of addition polymers from monomer structures and vice versa

Condensation polymers

  • understand that condensation polymers may be formed by reactions between dicarboxylic acids and diols, between dicarboxylic acids and diamines and between amino acids
  • know the linkage of the repeating units of polyesters (e.g. Terylene) and polyamides (e.g. nylon 6,6 and Kevlar)

Biodegradability and disposal of polymers 

  • understand that polyalkenes are chemically inert and therefore non-biodegradable
  • understand that polyesters and polyamides can be broken down by hydrolysis and are, therefore, biodegradable (mechanisms not required)
  • appreciate the advantages and disadvantages of different methods of disposal of polymers
  • appreciate the advantages and disadvantages of recycling polymers

Organic Synthesis and Analysis

Organic Synthesis and Analysis

Applications

  • be able to deduce how to synthesise organic compounds using the reactions in this specification
  • be able to identify organic functional groups using the reactions in the specification

Structure Determination

Structure Determination

Data sources

  • be able to use data from all the analytical techniques listed below to determine the structure of specified compounds

Mass spectrometry

  • understand that the fragmentation of a molecular ion M+• X+ + Ygives rise to a characteristic relative abundance spectrum that may give information about the structure of the molecule (rearrangement processes not required)
  • know that the more stable X+ species give higher peaks, limited to carbocation and acylium (RCO+) ions

Infrared spectroscopy

  • be able to use spectra to identify functional groups in this specification

Nuclear magnetic resonance spectroscopy

  • understand that nuclear magnetic resonance gives information about the position of 13C or 1H atoms in a molecule
  • understand that 13C n.m.r. gives a simpler sprectrum than 1H n.m.r.
  • know the use of the scale for recording chemical shift
  • understand that chemical shift depends on the molecular environment
  • understand how integrated spectra indicate the relative numbers of 1H atoms in different environments
  • understand that 1H n.m.r. spectra are obtained using samples dissolved in proton-free solvents (e.g. deuterated solvents and CCl4)
  • understand why tetramethylsilane (TMS) is used as a standard
  • be able to use the n +1 rule to deduce the spin–spin splitting patterns of adjacent, non-equivalent protons, limited to doublet, triplet and quartet formation in simple aliphatic compounds

Chromatography

  • know that gas-liquid chromatography can be used to separate mixtures of volatile liquids
  • know that separation by column chromatography depends on the balance between solubility in the moving phase and retention in the stationary phase

Unit 5 - Energetics, Redox and Inorganic Chemistry

Thermodynamics

Thermodynamics

Enthalpy change (∆H)

  • be able to define and apply the terms enthalpy of formation, ionisation enthalpy, enthalpy of atomisation of an element and of a compound, bond dissociation enthalpy, electron affinity, lattice enthalpy (defined as either lattice dissociation or lattice formation), enthalpy of hydration and enthalpy of solution
  • be able to construct Born–Haber cycles to calculate lattice enthalpies from experimental data. Be able to compare lattice enthalpies from Born–Haber cycles with those from calculations based on a perfect ionic model to provide evidence for covalent character in ionic compounds
  • be able to calculate enthalpies of solution for ionic compounds from lattice enthalpies and enthalpies of hydration
  • be able to use mean bond enthalpies to calculate an approximate value of ∆H for other reactions
  • be able to explain why values from mean bond enthalpy calculations differ from those determined from enthalpy cycles

Free-energy change (∆G) and entropy change (∆S)

  • understand that ∆H, whilst important, is not sufficient to explain spontaneous change (e.g. spontaneous endothermic reactions)
  • understand that the concept of increasing disorder (entropy change ∆S) accounts for the above deficiency, illustrated by physical change (e.g. melting, evaporation) and chemical change (e.g. dissolution, evolution of CO2 from hydrogencarbonates with acid)
  • be able to calculate entropy changes from absolute entropy values
  • understand that the balance between entropy and enthalpy determines the feasibility of a reaction; know that this is given by the relationship
    G = ∆HTS (derivation not required).
    be able to use this equation to determine how ∆G varies with temperature
    be able to use this relationship to determine the temperature at which a reaction is feasible

Periodicity

Periodicity

Study of the reactions of Period 3 elements Na – Ar to illustrate periodic trends

  • be able to describe trends in the reactions of the elements with water, limited to Na and Mg
  • be able to describe the trends in the reactions of the elements
  • Na, Mg, Al, Si, P and S with oxygen, limited to the formation
    of Na2O, MgO, Al2O3, SiO2, P4O10 and SO2.

A survey of the acid base properties of the oxides of Period 3 elements

  • be able to explain the link between the physical properties of the highest oxides of the elements Na – S in terms of their structure and bonding
  • be able to describe the reactions of the oxides of the elements Na – S with water, limited to Na2O, MgO, Al2O3, SiO2, P4O10, SO2 and SO3
  • know the change in pH of the resulting solutions across the Period
  • be able to explain the trends in these properties in terms of the type of bonding present
  • be able to write equations for the reactions which occur between these oxides and given simple acids and bases

Redox Equilibria

Redox Equilibria

Redox equations

  • be able to apply the electron transfer model of redox, including oxidation states and half equations to d block elements

Electrode potentials

  • know the IUPAC convention for writing half-equations for electrode reactions
  • know and be able to use the conventional representation of cells
  • understand how cells are used to measure electrode potentials by reference to the standard hydrogen electrode
  • know the importance of the conditions when measuring the electrode potential, E (Nernst equation not required)
  • know that standard electrode potential, Eo, refers to conditions of 298 K, 100 kPa and 1.00 mol dm−3 solution of ions

Electrochemical series

  • know that standard electrode potentials can be listed as an electrochemical series
  • be able to use Eo values to predict the direction of simple redox reactions and to calculate the e.m.f. of a cell

Electrochemical cells

  • appreciate that electrochemical cells can be used as a commercial source of electrical energy
  • appreciate that cells can be non-rechargeable (irreversible), rechargeable and fuel cells
  • be able to use given electrode data to deduce the reactions occurring in non-rechargeable and rechargeable cells and to deduce the e.m.f. of a cell
  • understand the electrode reactions of a hydrogen-oxygen fuel cell and appreciate that a fuel cell does not need to be electrically recharged
  • appreciate the benefits and risks to society associated with the use of these cells

Transition Metals

Transition Metals

General properties of transition metals

  • know that transition metal characteristics of elements Ti – Cu arise from an incomplete d sub-level in atoms or ions
  • know that these characteristics include complex formation, formation of coloured ions, variable oxidation state and catalytic activity

Complex formation

  • be able to define the term ligand
  • know that co-ordinate bonding is involved in complex formation
  • understand that a complex is a central metal ion surrounded by ligands
  • know the meaning of co-ordination number
  • understand that ligands can be unidentate (e.g. H2O, NH3 and Cl )
    or bidentate (e.g. NH2CH2CH2NH2 and C2O42- )
    or multidentate (e.g. EDTA4– )
  • know that haem is an iron(II) complex with a multidentate ligand

Shapes of complex ions

  • know that transition metal ions commonly form octahedral complexes with small ligands (e.g. H2O and NH3)
  • know that transition metal ions commonly form tetrahedral complexes with larger ligands (e.g. Cl )
  • know that square planar complexes are also formed, e.g. cisplatin
  • know that Ag+ commonly forms the linear complex [Ag(NH3)2]+ as used in Tollens' reagent

Formation of coloured ions

  • know that transition metal ions can be identified by their colour, limited to the complexes in this unit
  • know that colour changes arise from changes in oxidation state, co-ordination number and ligand
  • know that colour arises from electronic transitions from the ground state to excited states: ∆E = hν
  • appreciate that this absorption of visible light is used in spectrometry to determine the concentration of coloured ions

Variable oxidation states

  • know that transition elements show variable oxidation states
  • know that Cr3+ and Cr2+ are formed by reduction of Cr2O72- by zinc in acid solution
  • know the redox titration of Fe2+ with MnO4- and Cr2O72- in acid solution
  • be able to perform calculations for this titration and for others when the reductant and its oxidation product are given
  • know the oxidation of Co2+ by air in ammoniacal solution
  • know the oxidation in alkaline solution of Co2+ and Cr3+ by H2O2

Catalysis

  • know that transition metals and their compounds can act as heterogeneous and homogeneous catalysts

Heterogeneous

  • know that a heterogeneous catalyst is in a different phase from the reactants and that the reaction occurs at the surface
  • understand the use of a support medium to maximise the surface area and minimise the cost (e.g. Rh on a ceramic support in catalytic converters)
  • understand how V2O5 acts as a catalyst in the Contact Process
  • know that a Cr2O3 catalyst is used in the manufacture of methanol from carbon monoxide and hydrogen
  • know that Fe is used as a catalyst in the Haber Process
  • know that catalysts can become poisoned by impurities and consequently have reduced efficiency; know that this has a cost implication (e.g. poisoning by sulfur in the Haber Process and by lead in catalytic converters in cars)

Homogeneous

  • know that when catalysts and reactants are in the same phase, the reaction proceeds through an intermediate species (e.g. the reaction between I and S2O82- catalysed by Fe2+ and autocatalysis by Mn2+ in reactions of C2O42- with MnO4-)

Other applications of transition metal complexes

  • understand the importance of variable oxidation states in catalysis; both heterogeneous and homogeneous catalysts
  • understand that Fe(II) in haemoglobin enables oxygen to be transported in the blood, and why CO is toxic
  • know that the Pt(II) complex cisplatin is used as an anticancer drug
  • appreciate the benefits and risks associated with this drug
  • understand that [Ag(NH3)2]+ is used in Tollens' reagent to distinguish between aldehydes and ketones

Reactions of Inorganic Compounds in Aqueous Solution

Reactions of Inorganic Compounds in Aqueous Solution

Lewis acids and bases

  • know the definitions of a Lewis acid and Lewis base; understand the importance of lone pair electrons in co-ordinate bond formation

Metal-aqua ions

  • know that metal–aqua ions are formed in aqueous solution:

    [M(H2O)6]2+, limited to M = Fe, Co and Cu

    [M(H2O)6]3+, limited to M = Al, Cr and Fe

Acidity or hydrolysis reactions

  • understand the equilibria

    and

    to show generation of acidic solutions with M3+, and very weakly acidic solutions with M2+
  • understand that the acidity of [M(H2O)6]3+ is greater than that of [M(H2O)6]2+ in terms of the (charge/size ratio) of the metal ion
  • be able to describe and explain the simple test-tube reactions of
    M2+ (aq) ions, limited to M = Fe, Co and Cu,
    and of M3+ (aq) ions,
    limited to M = Al, Cr and Fe, with the bases
    OH-, NH3 and CO32-
  • know that MCO3 is formed but that M2(CO3)3 is not formed
  • know that some metal hydroxides show amphoteric character by dissolving in both acids and bases (e.g. hydroxides of Al3+ and Cr3+)
  • know the equilibrium reaction

Substitution reactions

  • understand that the ligands NH3 and H2O are similar in size and are uncharged, and that ligand exchange occurs without change of co-ordination number (e.g. Co2+ and Cr3+)
  • know that substitution may be incomplete (e.g. the formation of [Cu(NH3)4(H2O)2]2+)
  • understand that the Cl− ligand is larger than these uncharged ligands and that ligand exchange can involve a change of co-ordination number (e.g. Co2+ and Cu2+)
  • know that substitution of unidentate ligand with a bidentate or a multidentate ligand leads to a more stable complex
  • understand this chelate effect in terms of a positive entropy change in these reactions

Unit 6 - Investigative and Practical Skills in A2 Chemistry

Investigative and practical skills in A2 Chemistry

Investigative and practical skills in A2 Chemistry

Candidates should carry out experimental and investigative activities in order to develop their practical skills. Experimental and investigative activities should be set in contexts appropriate to, and reflect the demand of, the A2 content. These activities should allow candidates to use their knowledge and understanding of Chemistry in planning, carrying out, analysing and evaluating their work.

The content of Units 4 and 5 provide a basis for different practical topics which may be used for experimental and investigative skills. The experience of dealing with such activities will develop the skills required for the assessment of these skills in the Unit. Examples of suitable experiments that could be considered throughout the course will be provided in the Teaching and learning resources web pages.

It is expected that candidates will be able to use and be familiar with 'standard' laboratory equipment which is deemed suitable at A2 level, throughout their experiences of carrying out their practical activities.

The skills developed in the course of their practical activities are elaborated further in the How Science Works section of this specification.

In the course of their experimental work, candidates should learn to

  • demonstrate and describe ethical, safe and skilful practical techniques
  • process and select appropriate qualitative and quantitative methods
  • make, record and communicate reliable and valid observations
  • make measurements with appropriate precision and accuracy
  • analyse, interpret, explain and evaluate the methodology, results and impact of their own and others' experimental and investigative activities in a variety of ways.

The Centre-Assessed Option, Route T

The practical and investigative skills will be centre assessed through two methods

  • Investigative Skills Assignment (ISA).
  • Practical Skills Assessment (PSA).

The ISA will require candidates to undertake practical work, collect and process data and use it to answer questions in a written test (ISA test) (see Section 3.8 'Guidance on Internal Assessment').

The PSA will be based around a centre assessment, throughout the A2 course, of the candidate's ability to follow and undertake certain standard practical activities across the three areas of Chemistry: Inorganic, Organic and Physical. These practical activities are listed on the next page.

The Externally Marked Option, Route X

The practical and investigative skills will be externally assessed through

  • Practical Skills Verification (PSV) and
  • Externally Marked Practical Assignment (EMPA).

The PSV will require candidates to undertake the practical activities identified on the next page, in order to gain experience of a wide range of practical skills. These activities must allow a candidate suitable opportunity to demonstrate safe and skilful practice, as well as producing reliable and valid observations. AQA will require teacher verification, by means of a tick box on the front cover of the EMPA written test, that a candidate is experienced in these skills.

The EMPA, in a similar way to the ISA, will require candidates to undertake practical work, collect and process data and use it to answer questions in a written test (EMPA test) (see section 3.8 'Guildance on Internal Assessment').

Practical Skills Assessment

The PSA is designed to credit candidates for the practical work they undertake naturally as part of the course. It is expected that candidates will complete at least two practical activities from each of the three areas of Chemistry listed below.

A2 Inorganic Chemistry

Task Possible context
Carry out a redox titration The analysis of iron tablets by titration using acidified potassium manganate(VII)
Investigate the chemistry of transition metal compounds in a series of experiments The chemistry of copper compounds
Prepare an inorganic complex The preparation of hexaamminecobalt(III) chloride or the preparation of iron(II) ethandioate

A2 Physical Chemistry

Task Possible context
Carry out a kinetic study to determine the order of a reaction An iodine clock experiment e.g. the reaction of sulfite ions with iodate(V) ions
Determine an equilibrium constant Determine a value of Kc for the reaction of ethanol with ethanoic acid.
Investigate how pH changes when a weak acid reacts with a strong base or when a strong acid reacts with a weak base. Determine the pH curve for ethanoic acid reacting with sodium hydroxide

A2 Organic Chemistry

Task Possible context
Prepare a solid organic compound The preparation of aspirin
Purify an organic solid The recrystallisation of impure benzenecarboxylic acid from hot water
Test the purity of an organic solid Determine the melting point of benzenecarboxylic acid

How Science Works

How Science works

How Science works

How Science Works is an underpinning set of concepts and is the means whereby students come to understand how scientists investigate scientific phenomena in their attempts to explain the world about us. Moreover, How Science Works recognises the contribution scientists have made to their own disciplines and to the wider world.

Further, it recognises that scientists may be influenced by their own beliefs and that these can affect the way in which they approach their work. Also, it acknowledges that scientists can and must contribute to debates about the uses to which their work is put and how their work influences decisionmaking in society.

In general terms, it can be used to promote students' skills in solving scientific problems by developing an understanding of:

  • the concepts, principles and theories that form the subject content
  • the procedures associated with the valid testing of ideas and, in particular, the collection, interpretation and validation of evidence
  • the role of the scientific community in validating evidence and also in resolving conflicting evidence.

As students become proficient in these aspects of How Science Works, they can also engage with the place and contribution of science in the wider world. In particular, students will begin to recognise:

  • the contribution that scientists can make to decision-making and the formulation of policy
  • the need for regulation of scientific enquiry and how this can be achieved
  • how scientists can contribute legitimately to debates about those claims which are made in the name of science.

An understanding of How Science Works is a requirement for this specificatiion and is set out in the following points which are taken direct from the GCE AS and A Level subject criteria for science subjects. Each point is expanded in the context of Chemistry. The specification references given illustrate where the example is relevant and could be incorporated.

Use theories, models and ideas to develop and modify scientific explanations

Use theories, models and ideas to develop and modify scientific explanations

Scientists use theories and models to attempt to explain observations. These theories or models can form the basis for scientific experimental work.

Scientific progress is made when validated evidence is found that supports a new theory or model.

Examples in this specification include:

  • the use of ionisation energy plots as evidence for electron arrangement in shells and subshells (AS Unit 1, 3.1.1)
  • experiments with cells confirm that electrons are transferred in redox reactions (A2 Unit 5, 3.5.3)

Use knowledge and understanding to pose scientific questions, define scientific

Use knowledge and understanding to pose scientific questions, define scientific problems, present scientific arguments and scientific ideas

Scientists use their knowledge and understanding when observing objects and events, in defining a scientific problem and when questioning the explanations of themselves or of other scientists.

Scientific progress is made when scientists contribute to the development of new ideas, materials and theories.

Examples in this specification include:

  • explanation of the origin of the hole in the ozone layer (AS Unit 2, 3.2.8)
  • Entropy as a concept to explain spontaneous reactions (A2 Unit 5, 3.5.2)

Use appropriate methodology, including ICT, to answer scientific questions and solve

Use appropriate methodology, including ICT, to answer scientific questions and solve scientific problems

Observations ultimately lead to explanations in the form of hypotheses. In turn, these hypotheses lead to predictions that can be tested experimentally. Observations are one of the key links between the 'real world' and the abstract ideas of science.

Once an experimental method has been validated, it becomes a protocol that is used by other scientists.

ICT can be used to speed up, collect, record and analyse experimental data.

Examples in this specification include:

  • Many opportunities permeating throughout the Practical and Investigative Skills units (Unit 3 and Unit 6)

Carry out experimental and investigative activities, including appropriate risk

Carry out experimental and investigative activities, including appropriate risk management, in a range of contexts

Scientists perform a range of experimental skills that include manual and data skills (tabulation, graphical skills etc).

Scientists should select and use equipment that is appropriate when making accurate measurements and should record these measurements methodically.

Scientists carry out experimental work in such a way as to minimise the risk to themselves, to others and to the materials, including organisms, used.

Examples in this specification include:

  • Many opportunities permeating throughout the Practical and Investigative Skills units (Unit 3 and Unit 6)

Analyse and interpret data to provide evidence, recognising correlations and causal

Analyse and interpret data to provide evidence, recognising correlations and causal relationships

Scientists look for patterns and trends in data as a first step in providing explanations of phenomena. The degree of uncertainty in any data will affect whether alternative explanations can be given for the data.

Anomalous data are those measurements that fall outside the normal, or expected, range of measured values. Decisions on how to treat anomalous data should be made only after examination of the event.

In searching for causal links between factors, scientists propose predictive theoretical models that can be tested experimentally. When experimental data confirm predictions from these theoretical models, scientists become confident that a causal relationship exists.

Examples in this specification include:

  • the use of enthalphy of combustion data for a range of alcohols in the development of the idea of mean bond enthalpies (AS Unit 2, 3.2.1)
  • the recognition that entropy change is an important factor in determining the direction of spontaneous reaction (A2 Unit 5, 3.5.1 and 3.5.5)

Evaluate methodology, evidence and data, and resolve conflicting evidence

Evaluate methodology, evidence and data, and resolve conflicting evidence

The validity of new evidence, and the robustness of conclusions that stem from them, is constantly questioned by scientists.

Experimental methods must be designed adequately to test predictions.

Solutions to scientific problems are often developed when different research teams produce conflicting evidence. Such evidence is a stimulus for further scientific investigation, which involves refinements of experimental technique or development of new hypotheses.

Examples in this specification include:

  • the importance of bond polarity and carbon-halogen bond enthalpy as factors in determining the rate of hydrolysis of haloalkanes (AS Unit 1, 3.1.1)
  • the use of thermochemical evidence from enthalpies of hydrogenation enthalpies as support for the structure of benzene (A2 Unit 4, 3.4.6)

Appreciate the tentative nature of scientific knowledge

Appreciate the tentative nature of scientific knowledge

Scientific explanations are those that are based on experimental evidence which is supported by the scientific community.

Scientific knowledge changes when new evidence provides a better explanation of scientific observations.

Examples in this specification include:

  • the increase in greenhouse gases that may cause global warming (AS Unit 1, 3.1.6)
  • the reactions of metal-aqua ions acting as Lewis bases (A2 Unit 5, 3.5.5)

Communicate information and ideas in appropriate ways using appropriate terminology

Communicate information and ideas in appropriate ways using appropriate terminology

By sharing the findings of their research, scientists provide the scientific community with opportunities to replicate and further test their work, thus either confirming new explanations or refuting them.

Scientific terminology avoids confusion amongst the scientific community, enabling better understanding and testing of scientific explanations.

Examples in this specification include:

  • IUPAC rules for naming organic compounds have been adopted globally (AS Unit 1, 3.1.5)
  • experiments with cells confirm that electrons are transferred in redox reactions (A2, Unit 5, 3.5.3)

Consider applications and implications of science and appreciate their associated benefits and risks

Consider applications and implications of science and appreciate their associated benefits and risks

Scientific advances have greatly improved the quality of life for the majority of people. Developments in technology, medicine and materials continue to further these improvements at an increasing rate.

Scientists can predict and report on some of the beneficial applications of their experimental findings.

Scientists evaluate, and report on, the risks associated with the techniques they develop and applications of their findings.

Examples in this specification include:

  • the benefits and risks of using chlorine in water treatment (AS Unit 2, 3.2.5)
  • The use of hydrogen-oxygen fuel cells as a source of energy and the hazards associated with their use (A2 Unit 5, 3.5.4)

Consider ethical issues in the treatment of humans, other organisms and the environment

Consider ethical issues in the treatment of humans, other organisms and the environment

Scientific research is funded by society, either through public funding or through private companies that obtain their income from commercial activities. Scientists have a duty to consider ethical issues associated with their findings.

Individual scientists have ethical codes that are often based on humanistic, moral and religious beliefs.

Scientists are self-regulating and contribute to decision making about what investigations and methodologies should be permitted.

Examples in this specification include:

  • the environmental and economic advantages of recycling scrap metal (AS Unit 2, 3.2.7)
  • how the relative biodegradability of polymers affects their disposal or reuse ( A2, Unit 4, 3.4.9)

Appreciate the role of the scientific community in validating new knowledge and ensuring integrity

Appreciate the role of the scientific community in validating new knowledge and ensuring integrity

The findings of scientists are subject to peer review before being accepted for publication in a reputable scientific journal.

The interests of the organisations that fund scientific research can influence the direction of research. In some cases the validity of those claims may also be influenced

Examples in this specification include:

  • the identification of acid rain as a problem (AS Unit 2, 3.2.7)
  • the production of biofuels as carbon neutral fuels (A2 Unit 4, 3.4.4)

Appreciate the ways in which society uses science to inform decision making

Appreciate the ways in which society uses science to inform decision making

Scientific findings and technologies enable advances to be made that have potential benefit for humans.

In practice, the scientific evidence available to decision makers may be incomplete.

Decision makers are influenced in many ways, including by their prior beliefs, their vested interests, special interest groups, public opinion and the media, as well as by expert scientific evidence

Examples in this specification include:

  • the identification of the release of CO and NO as a problem and the development of catalytic converters to counteract this (AS Unit 2, 3.2.8)
  • the different properties of enantiomers can give rise to different chemical reactions in the body, for example the optical isomers of thalidomide (A2 Unit 4, 3.4.4)

Guidance on Internal Assessment

Introduction

Introduction

The GCE Sciences share a common approach to centre assessment. This is based on the belief that assessment should encourage practical activity in science, and that practical activity should encompass a broad range of activities. This section must be read in conjunction with information in the Teacher Resource Bank.

Practical and Investigative Skills are assessed in Unit 3 and Unit 6, worth, respectively, 20% of the AS Award (and 10% of the Advanced Level Award) and 10% of the full Advanced Level Award.

There are two routes for the assessment of Practical and Investigative Skills

Either

Route T: Practical Skills Assessment (PSA) + Investigative Skills Assignment (ISA) - Teacher-marked

Or

Route X: Practical Skills Verification (PSV) + Externally Marked Practical Assignment (EMPA) - AQA- marked.

Both routes to assessment are available at AS and A2.

Centres can not make entries for the same candidate for both assessment routes [T and X] in the same examination series.

Centre Assessed Route T (PSA/ISA)

Centre Assessed Route T (PSA/ISA)

Each centre assessed unit comprises

  • Practical Skills Assessment (PSA)
  • Investigative Skills Assignment (ISA).

The PSA consists of the centre's assessment of the candidate's ability to demonstrate practical skills throughout the course; thus, candidates should be encouraged to carry out practical and investigative work throughout the course of their study. This work should cover the skills and knowledge of How Science Works.

The ISA has two stages where candidates

  • undertake practical work, collect and process data
  • complete a written ISA test.

Each stage must be carried out under controlled conditions but may be scheduled at a time convenient to the centre. The written test must be completed in a single, uninterrupted session.

The ISA is set externally by AQA, but internally marked, with marking guidelines provided by AQA.

In a given academic year two ISAs at each of AS and A2 level will be provided.

Practical Skills Assessment (PSA)

Practical Skills Assessment (PSA)

Candidates are assessed throughout the course on practical skills, using a scale from 0 to 12. The mark submitted for practical skills should be judged by the teacher. Teachers may wish to use this section for formative assessment and should keep an ongoing record of each candidate's performance but the mark submitted should represent the candidate's practical abilities over the whole course.

The nature of the assessment

Since the skills in this section involve implementation, they must be assessed while the candidate is carrying out practical work. Practical activities are not intended to be undertaken as formal tests and supervisors can provide the level of guidance that would normally be given during teaching. In order to provide appropriate opportunities to demonstrate the necessary skills, instructions provided must not be too prescriptive but should allow candidates to make decisions for themselves, particularly concerning the conduct of practical work, their organisation and the manner in which equipment is used.

The tasks

Tasks are provided in the three areas of chemistry; inorganic, physical and organic chemistry.

AS level candidates should undertake at least two of the tasks from each of the three areas of chemistry. Each task will score a maximum of 2 marks aggregating to a total score out of 12 marks.

Only marks arising from those tasks designated as AS tasks may be submitted for AS Chemistry.

A2 level candidates should undertake at least two of the tasks from each of the three areas of chemistry. Each task will score a maximum of 2 marks aggregating to a total score out of 12 marks. Only marks arising from those tasks designated as A2 tasks may be submitted for A2 Chemistry.

At both AS and A2, centres may choose to carry out all of the available tasks, in which case, the best two marks from each area for each candidate should be counted towards the final mark.

A list of the AS and A2 PSA tasks is given in Sections 3.3 and 3.6, respectively. Detailed marking guidance including descriptors for 0, 1 and 2 marks for each PSA task is provided in Section 3.8.3. 

Candidates should be awarded marks which reflect their level of performance over the whole course.

AQA may wish to ask for further supporting evidence from centres in relation to the marks awarded for the PSA. Centres should therefore keep records of their candidates' performances in their practical activities throughout the course. (For example, a laboratory diary, log or tick sheet.)

Further guidance for the awarding of marks for the PSA will be provided in the Teacher Resource Bank.

Use of ICT during the PSA

Candidates are encouraged to use ICT where appropriate in the course of developing practical skills, for example in collecting and analysing data.

Investigative Skills Assignment (ISA)

Investigative Skills Assignment (ISA)

The Investigative Skills Assignment carries 38 marks and has two stages.

Stage 1: Collection and Processing of data

Candidates carry out practical work following an AQA task sheet. Centres may use the task sheet as described or may make minor suitable modifications to materials or equipment, following AQA guidelines. Any modifications made to the task sheet must be agreed in writing with the AQA Assessment Adviser. The task may be conducted in a normal timetabled lesson but must be under controlled conditions.

Candidates collect raw data and represent it in a table of their own design or make observations that are recorded on the Candidate Results Sheet. The candidates' work must be handed to the teacher at the end of the session. The teacher assesses the candidates' work following AQA marking guidelines.

There is no specified time limit for this stage.

Stage 2: The ISA written test

The ISA test should be taken as soon as convenient after completion of Stage 1, and under controlled conditions. Each candidate is provided with an ISA test and the candidate's completed material from Stage 1. The teacher uses the AQA marking guidelines to assess the ISA test.

The ISA test is in two Sections.

Section A

This consists of a number of questions relating to the candidate's own data.

Section B

At the start of this section, candidates are supplied with additional data on a related topic. A number of questions relating to analysis and evaluation of the data then follow.

The number of marks allocated to each section may vary slightly with each ISA test.

Use of ICT during the ISA

ICT may be used during the ISA Stages 1 and 2 but teachers should note any restrictions in the ISA marking guidelines or Teachers Notes. Use of the internet is not permitted.

Candidates absent for the practical work

A candidate absent for the practical work (Stage 1) should be given an opportunity to carry out the practical work before they sit the ISA test. This may be with another group or at a different time. In extreme circumstancs, when such arrangements are not possible, the teacher may supply a candidate with class data. In this case candidates cannot be awarded marks for Stage 1, but can still be awarded marks for Stage 2 of the assessment.

Material from AQA

For each ISA, AQA will provide:

  • Teachers' Notes
  • Task sheet
  • ISA test
  • Marking guidelines.

This material must be kept under secure conditions within the centre. If it is to be used in more than one session, then the centre must ensure security of the material between sessions. Further details regarding this material will be provided.

Security of assignments

All ISA materials, including marked ISAs, should be treated like examination papers and kept under secure conditions until the publication of results.

General Information Route T

General Information Route T

Administration

In any year a candidate may attempt either or both of the two ISAs.

For each candidate, the teacher should submit to AQA a total mark comprising:

  • The PSA mark
  • the better ISA mark (if two have been attempted).

The ISA component of this mark must come from one ISA only, i.e. the marks awarded for stages of different ISAs cannot be combined.

Candidates may make only one attempt at a particular ISA. Redrafting is not permitted at any stage during the ISA.

The total mark must be submitted to AQA by the due date in the academic year for which the ISA was published.

Work to be submitted

For each candidate in the sample the following materials must be submitted to the moderator by the deadline issued by AQA.

  • the candidate's data from Stage 1 (on the Candidate Result Sheet)
  • the ISA written test, which includes the Candidate Record Form, showing the marks for the ISA and the PSA.

In addition each centre must provide

  • Centre Declaration Sheet
  • Details of any amendments to the task sheet with information supporting the changes from the AQA Assessment Adviser, must be notified to the moderator
  • For each group of candidates, a completed Teacher Results Sheet.

Working in groups

For the PSA candidates may work in groups provided that any skills being assessed are the work of individual candidates. For the ISA further guidance will be provided in the Teacher Notes.

Other information

Section 6 of this specification outlines further guidance on the supervision and authentication of centre assessed units.

Section 6 also provides information in relation to the internal standardisation of marking for these units.

Further support

AQA supports the units in a number of ways.

  • AQA holds annual standardising meetings on a regional basis for all internally assessed components. Section 6 of this specification provides further details about these meetings
  • A Teacher Resource Bank which includes further information and guidance
  • Assessment Advisers are appointed by AQA to provide advice on internally assessed units. Every centre is allocated an Assessment Adviser.

The Assessment Advisers can provide guidance on

– issues relating to the carrying out of tasks for assessment

– application of marking guidelines

Any amendments to the ISA task sheet must be discussed with the Assessment Adviser and confirmation of the amendments made must be submitted to the AQA moderator.

Externally Marked Route X (PSV/EMPA)

Externally Marked Route X (PSV/EMPA)

The practical and investigative skills will be assessed through

  • Practical Skills Verification (PSV) and
  • Externally Marked Practical Assignment (EMPA).

The PSV requires teachers to verify their candidates' ability to demonstrate safe and skilful practical techniques and make valid and reliable observations.

The EMPA has two stages where candidates

  • Undertake a themed task
  • Complete a written EMPA test

Each stage must be carried out under controlled conditions but may be at a time convenient to the centre. The written test must be completed in a single uninterrupted session.

The EMPA is set and marked by AQA. Only one EMPA at AS and one at A2 will be provided in a given academic year. AQA will stipulate a period of time during which the EMPA (task and written test) must be completed.

Practical Skills Verification

Practical Skills Verification

Candidates following this route must undertake the practical activities outlined in sections 3.3 for AS or 3.6 for A2 in order to allow candidates suitable opportunities to demonstrate safe and skilful practical techniques and to make reliable and valid observations. The teacher will confirm on the Candidate Record Form, for each candidate that this requirement has been met. Failure to complete the tick box will lead to a mark of zero being awarded to the candidate for the whole of this unit. Knowledge and understanding of the skills in Section 3.3 and 3.6 will be assessed in Section C of the EMPA  written tests. 

Tasks are provided in the three areas of chemistry; inorganic, physical and organic chemistry. Candidates should undertake at least two of the task form from each of the three areas of chemistry.

In order to provide appropriate opportunities to demonstrate the necessary skills, teachers must not be too prescriptive to the instructions they provide but should allow candidates to make decisions for themselves, particularly concerning the conduct of practical work, their organisation and the manner in which equipment is used.

Candidates should be encouraged to carry out practical and investigative work throughout the course. This work should cover the skills and knowledge of How Science Works.

Further guidance for conducting practical activities for the PSV will be provided in the Teacher Resource Bank.

ICT

Candidates may use ICT where appropriate in the course of developing practical skills, for example in collecting and analysing data.

Externally Marked Practical Assignment (EMPA)

Externally Marked Practical Assignment (EMPA)

The Externally Marked Practical Assignment carries 50 marks and has two stages.

Stage 1: Themed task, collection and processing of data

Candidates carry out practical work following AQA task sheets. The tasks may be conducted in normal timetabled lessons and at a time convenient to the centre but must be under controlled conditions. Candidates collect raw data and represent it in a table of their own design or make observations that are recorded on Task Sheet 1 and Task Sheet 2. The candidates' work must be handed to the teacher at the end of each session.

Centres may use the task sheets, as described, or may make minor suitable modifications to materials or equipment following AQA guidelines. Any modifications made to the task sheets must be agreed in writing with the Assessment Adviser and details must be provided to the AQA Examiner.

There is no specified time limit for this stage.

Stage 2: The EMPA written test

The EMPA test should be taken as soon as convenient after completion of Stage 1 and under controlled conditions. Each candidate is provided with an EMPA test and the candidate's completed material from Stage 1.

The EMPA test is in three Sections.

Section A

This consists of a number of questions relating to the candidate's own data.

Section B

At the start of this section, candidates are supplied with additional data on a related topic. A number of questions relating to analysis and evaluation of the data then follow.

Section C

Candidates answer questions based on knowledge and understanding of the processes outlined in section 3.3 for AS and section 3.6 for A2. 

The number of marks allocated to each section may vary with each EMPA test.

Use of ICT during the EMPA

ICT may be used during the EMPA Stages 1 and 2 but teachers should note any restrictions in the Teachers' Notes. Use of the internet is not permitted.

Candidates absent for the practical work

A candidate absent for the practical work (Stage 1) should be given an opportunity to carry out the practical work before they sit the EMPA test. This may be with another group or at a different time. In extreme circumstances, when such arrangements are not possible the teacher may supply a candidate with class data. This must be noted on the Candidate Record Form. In this case the candidate cannot be awarded marks for Stage 1, but can still be awarded marks for Stage 2 of the assessment.

Material from AQA

For each EMPA, AQA will provide:

  • Teachers' Notes
  • Task sheets
  • EMPA test

When received, this material must be kept under secure conditions. If it is to be used in more than one session, then the centre must ensure security of material between sessions. Further details regarding this material will be provided.

Security of assignments

Completed EMPAs should be treated like examination papers and kept under secure conditions until sent to the Examiner. All other EMPA materials should be kept under secure conditions until the publication of results.

General Information Route X

General Information Route X

Administration

Only one EMPA will be available in any year at AS and at A2. AQA will stipulate a period of time during which the EMPA (task and test) must be completed.

Candidates may make only one attempt at a particular EMPA and redrafting is not permitted at any stage during the EMPA.

Work to be submitted

The material to be submitted to the examiner for each candidate consists of

  • the completed Task Sheet 1 and Task Sheet 2
  • the EMPA written test, which includes the Candidate Record Form, showing the PSV verification of safe and skilful practical techniques and reliable and valid observations.

In addition each centre must provide

  • Centre Declaration Sheet
  • Details of any amendments to the task sheet with confirmation supporting the changes from the Assessment Adviser
  • For each group of candidates, a completed Teacher Results Sheet.

Working in groups

For the PSV candidates may work in groups provided that any skills being assessed are the work of individual candidates. For the EMPA further guidance will be provided but the opportunity for group work will not be a common feature.

Other information

Section 6 of this specification outlines further guidance on the supervision and authentication of Internally assessed units.

Further support

AQA supports centres in a number of ways.

  • A Teacher Resource Bank which includes further information and guidance
  • Assessment Advisers are appointed by AQA to provide advice on internally assessed units. Every centre is allocated an Assessment Adviser.

The Assessment Advisers can provide guidance on issues relating to the carrying out of tasks for assessment. Any amendments to the EMPA task sheet must be discussed with the AQA Assessment Adviser and confirmation of the amendments made must be submitted to the AQA Examiner.

3.8.3 General Marking Guidance for each PSA

Centres should bear in mind that satisfactory completion of a PSA task by the candidate should be judged in the context of an ability to work safely and in an organised manner, when demonstrating appropriate manipulative skills. Each task should be graded on a three point scale (0, 1 or 2 marks) with the following general guidelines for the award of each point on the scale. 

Further support

AQA supports the centre assessed units in a number of ways.

* AQA holds annual standardising meetings on a regional basis for all centre assessed components. Section 6 of this specification provides further details about these meetings

* A Teacher Resource Bank which includes further information and guidance from the Principal Moderator.

* Assessment Advisers are appointed by AQA to provide advice on centre assessed units. Every centre is allocated an Assessment Adviser. Contact details for your Assessment Adviser can be obtained by e-mailing your centre name and number to chemistry-gce@aqa.org.uk. The Assessment Advisers can provide guidance on

–  issues relating to the carrying out of 

    assignments for assessment

–  application of marking guidelines

–  administrative issues related to the centre

    assessed units.

3.8.4 General Marking Guidance for each PSA

3.8.4 General Marking Guidance for each PSA

Centres should bear in mind that satisfactory completion of a PSA task by the candidate should be judged in the context of an ability to work safely and in an organised manner, when demonstrating appropriate manipulative skills. 

Each task should be graded on a three point scale (0, 1 or 2 marks) with the following general guidelines for the award of each point on the scale.

 

2 marks Candidates are able to follow a set of instructions for the task in a safe and organised way. Measurements are precise and within the expected range. Candidates require minimal additional guidance to carry out the task in a competent manner and are able to produce an outcome which is within the expected tolerance for the activity or produce a set of results, most of which are correct.
1 marks Candidates are able to follow a set of instructions for the task in a reasonably safe way, but could be better organised. Measurements are imprecise or outside the expected range. Candidates require some additional guidance to carry out the task to a standard which is considered appropriate and produce an outcome, which, whilst acceptable, may not be within the expected tolerance for the activity or produce a set of results, only some of which are correct.
0 marks Candidates have significant difficulty in following a set of instructions for the task and their work is poorly organised or unsafe. Measurements are imprecise or outside the expected range. Candidates require significant additional guidance to carry out the task to a standard which is considered appropriate and produce an outcome which is significantly outside the expected tolerance for the activity or produce a set of results, few of which are correct.

The following sections detail, for AS and A2, possible contexts and marking guidance for each area of chemistry

Practical Skills Assessment: AS Inorganic Chemistry

Practical Skills Assessment: AS Inorganic Chemistry

 

Task and possible contextSpecific marking guidance
Make up a volumetric solution
For example:

The preparation of a standard solution of sodium carbonate
2 marks: All areas of the task are carried out competently.
The weighing is precise and within the required range.
The transfer of solid to a graduated flask is done with care.
The solution is made up to the mark, accurately.

1 mark: One of the areas of the task is performed poorly.
The weighing is imprecise or outside the required range OR The transfer of solid to the graduated flask is careless OR The solution is made up inaccurately. (e.g. the flask is over-filled)

0 marks: At least two of the areas of the task are performed poorly.
 The weighing is imprecise or outside the required range.
The transfer of solid to the graduated flask is careless.
The solutiion is made up inaccurately.
Carry out a simple acid-base titration
For example:

Determine the concentration of unknown hydrochloric acid by titration
2 marks: All areas of the task are carried out competently. The burette is filled safely with the correct reagent (including below the tap).
The pipette and filler, burette and conical flask are all used correctly. The titration results are concordant and the average titre is judged accurate.

1 mark: One of the areas of the task is performed poorly.
The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap OR One of either, the pipette, pipette filler, burette or conical flask is not used correctly OR The titration results are not concordant or the average titre is inaccurate.

0 marks: At least two of the areas of the task are performed poorly.
The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap.
One of either, the pipette, pipette filler, burette or conical flask is not used correctly.
The titration results are not concordant or the average titre is inaccurate
Carry out some inorganic tests 
For example:

Tests for anions
2 marks: All areas of the task are carried out competently.
The quantities of reagents are appropriate.
The tests (heating, shaking etc.) are carried out safely and with due care.
Most of the observations are correct.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are inappropriate OR
The tests (heating, shaking etc.) are carried out in a careless manner OR
Only some of the observations are correct.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are inappropriate.
The tests (addition, heating, shaking etc.) are carried out in a careless manner. Few of the observations are correct.

Practical Skills Assessment: AS Physical Chemistry

Practical Skills Assessment: AS Physical Chemistry

 

Task and possible contextSpecific marking guidance
Measure an enthalpy change

For example:

Use Hess's law to find an unknown enthalpy change, such as the reaction of anhydrous copper(II) sulfate with water to produce hydrated crystals
2 marks: All areas of the task are carried out competently.
Masses and volumes are measured precisely and within the required range.
Initial/final temperatures are measured precisely and mixing is complete.
The results lead to an enthalpy change which is within the expected range.

1 mark: One of the areas of the task is performed poorly.
Masses or volumes are measured imprecisely or not in the required range OR
Temperatures are measured imprecisely or mixing is incomplete OR The results lead to an enthalpy change which is outside the expected range.

0 marks:  At least two of the areas of the task are performed poorly. Masses or volumes are measured imprecisely or not in the required range.
Temperatures are measured imprecisely or mixing is incomplete.
The results lead to an enthalpy change which is outside the expected range.
Determine the Mr of a volatile liquid or the Mr of a gas

For example:

Determine the Mr of hexane or the Mr of carbon dioxide
2 marks: All areas of the task are carried out competently.
The apparatus is weighed precisely and handled carefully.
The transfer of liquid or gas is carried out safely and with due care.
The apparatus is equilibrated and all necessary measurements taken.

1 mark: One of the areas of the task is performed poorly.
The apparatus is weighed imprecisely or handled without due care OR The transfer of liquid or gas is not carried out safely or with due care ORThe apparatus has not equilibrated or some measurements are not taken.

0 marks: At least two of the areas of the task are performed poorly.
 The apparatus is weighed imprecisely or handled without due care.
The transfer of liquid or gas is not carried out safely or with due care.
 The apparatus has not equilibrated or some measurements are not taken.
Investigate how the rate of a reaction changes with temperature

For example:

Investigate the rate of reaction of sodium thiosulfate with acid at different temperatures
2 marks: All areas of the task are carried out competently.
The quantities of reagents are appropriate and the apparatus is safe.
Heating is carried out with due care and only as long as necessary.
The change in the measured rate is within the expected range.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are inappropriate or the apparatus is unsafe OR Heating is carried out with insufficient care or longer than necessary OR The change in the measured rate is not within the expected range.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are inappropriate or the apparatus is unsafe. Heating is carried out with insufficient care or longer than necessary.
The change in the measured rate is not within the expected range

Practical Skills Assessment: AS Organic Chemistry

Practical Skills Assessment: AS Organic Chemistry

 

Task and possible contextSpecific marking guidance
Distil a product from a reaction
For example:

The preparation of ethanal from the oxidation of ethanol or the preparation of cyclohexene from cyclohexanol
2 marks: All areas of the task are carried out competently.
The apparatus set-up is safe and appropriate.
Heating is carried out with due care and only as long as necessary.
The yield of product is appropriate.

1 mark: One of the areas of the task is performed poorly.
The apparatus set-up is inappropriate OR
Heating is carried out with insufficient care or longer than necessary OR
The yield of product is inappropriate.

0 marks: At least two of the areas of the task are performed poorly. The apparatus set-up is inappropriate.
Heating is carried out with insufficient care or longer than necessary.
The yield of product is inappropriate.
Carry out some organic tests
For example:

Tests for alkene, alcohol, acid, aldehyde
2 marks: All areas of the task are carried out competently.
The quantities of reagents are appropriate.
The tests (heating, shaking etc.) are carried out safely and with due care.
Nearly all of the observations are correct.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are inappropriate OR
The tests (heating, shaking etc.) are carried out in a careless manner OR Only some of the observations are correct.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are inappropriate.
The tests (addition, heating, shaking etc.) are carried out in a careless manner.
Few of the observations are correct.
Investigate the combustion of alcohols
For example:

Use a calorimetric method to measure the enthalpies of combustion in an homologous series
2 marks: All areas of the task are carried out competently.
Masses and volumes are measured precisely and within the required range. Initial/final temperatures are measured precisely.
The range and trend in enthalpies is as expected for the series.

1 mark: One of the areas of the task is performed poorly.
Masses or volumes are measured imprecisely or not in the required range OR Temperatures are measured imprecisely OR
The range or trend in enthalpies is not as expected for the series.

0 marks: At least two of the areas of the task are performed poorly. Masses or volumes are measured imprecisely or not in the required range. Temperatures are measured imprecisely.
The range or trend in enthalpies is not as expected for the series.

Practical Skills Assessment: A2 Inorganic Chemistry

Practical Skills Assessment: A2 Inorganic Chemistry

 

Task and possible contextSpecific marking guidance
Carry out a redox titration

For example:

The analysis of iron tablets by titration using acidified potassium manganate(VII)
2 marks: All areas of the task are carried out competently.
The burette is filled safely with the correct reagent (including below the tap) The pipette and filler, burette and conical flask are all used correctly.
The titration results are concordant and the average titre is accurate.

1 mark: One of the areas of the task is performed poorly.
The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap OR
One of either the pipette, pipette filler, burette or conical flask is used incorrectly OR
The titration results are not concordant or the average titre is inaccurate.

0 marks: At least two of the areas of the task are performed poorly.
The burette is filled with the incorrect reagent or the funnel is left in or the burette is not filled below the tap.
One of either the pipette, filler, burette or conical flask is used incorrectly. The titration results are not concordant or the average titre is inaccurate.
Investigate the chemistry of transition metal compounds in a series of experiments

For example:

The chemistry of copper compounds
2 marks: All experiments are carried out competently.
The quantities of reagents are appropriate.
All experiments are carried out safely and with due care.
Nearly all of the observations are correct.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are inappropriate OR
Some of the experiments are carried out in a careless manner OR
Only some of the observations are correct.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are inappropriate.
Many of the experiments are carried out in a careless manner.
Few of the observations are correct.
Prepare an inorganic complex

For example:

The preparation of hexaamminecobalt(III) chloride
2 marks: All areas of the task are carried out competently.
The quantities of reagents are appropriate for the preparation.
The apparatus set-up for the preparation is safe and appropriate.
The experiment is carried out safely and produces an appropriate quantity and quality of product.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are inappropriate for the preparation OR
The apparatus set-up for each experiment is unsafe or inappropriate OR
The experiments are carried out with insufficient care or the yield is poor.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are inappropriate for the preparation.
The apparatus set-up for each experiment is unsafe or inappropriate.
The experiments are carried out with insufficient care or the yield is poor.

Practical Skills Assessment: A2 Physical Chemistry

Practical Skills Assessment: A2 Physical Chemistry

 

Task and possible contextSpecific marking guidance
Carry out a kinetic study to determine the order of a reaction

For example:

An iodine clock experiment e.g. the reaction of sulfite ions with iodate(V) ions
2 marks: All areas of the task are carried out competently.
The quantities of reagents are measured precisely.
Times are measured accurately and recorded precisely.
Sufficient values are on a good straight line and the order of reaction is in the expected range.

1 mark: One
of the areas of the task is performed poorly.
The quantities of reagents are measured imprecisely OR Times are measured inaccurately or recorded imprecisely OR The values are scattered or the order is not in the expected range.

0 marks: At least two
of the areas of the task are performed poorly.
The quantities of reagents are measured imprecisely.
Times are measured inaccurately or recorded imprecisely.
The values are scattered or the order is not in the expected range.
Determine an equilibrium constant

For example:

Determine a value of Kc for the reaction of ethanol with ethanoic acid
2 marks: All areas of the task are carried out competently.
The quantities of reagents are measured precisely.
The titrations are carried out with due care and data recorded precisely.
The value of the equilibrium constant is in the expected range.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are measured imprecisely OR
Titrations are carried out with insufficient care or data recorded imprecisely ORThe value of the equilibrium constant is not in the expected range.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are measured imprecisely.
Titrations are carried out with insufficient care or data recorded imprecisely. The value of the equilibrium constant is not in the expected range.
Investigate how pH changes when a weak acid reacts with a strong base or when a strong acid reacts with a weak base

For example:

Determine the pH curve for ethanoic acid reacting with sodium hydroxide
2 marks: All areas of the task are carried out competently.
The apparatus is used correctly.
The pH values are recorded correctly.
The pH changes are in the expected range.

1 mark: One of the areas of the task is performed poorly.
The apparatus is used incorrectly OR
The pH values are recorded incorrectly OR
The pH changes are not in the expected range.

0 marks: At least two of the areas of the task are performed poorly.
The apparatus is used incorrectly.
The pH values are recorded incorrectly.
The pH changes are not in the expected range.

Practical Skills Assessment: A2 Organic Chemistry

Practical Skills Assessment: A2 Organic Chemistry

 

Task and possible contextSpecific marking guidence
Prepare a solid organic compound

For example:

The preparation of aspirin
2 marks: All areas of the task are carried out competently.
The quantities of reagents are appropriate for the preparation.
The apparatus set-up for the preparation is safe and appropriate.
 The experiment is carried out safely and produces an appropriate quantity and quality of product.

1 mark: One of the areas of the task is performed poorly.
The quantities of reagents are inappropriate for the preparation OR
The apparatus set-up for each experiment is unsafe or inappropriate OR
The experiment is carried out with insufficient care or the yield is poor.

0 marks: At least two of the areas of the task are performed poorly.
The quantities of reagents are inappropriate for the preparation.
The apparatus set-up for each experiment is unsafe or inappropriate.
The experiment is carried out with insufficient care or the yield is poor.
Purify an organic solid

For example:

The recrystallisation of impure benzenecarboxylic acid from hot water
2 marks: All areas of the task are carried out competently.
The quantity of solvent is appropriate.
The recrystallisation process is carried out safely and with due care.
The quantity and quality of recrystallised product are both appropriate.

1 mark: One of the areas of the task is performed poorly.
The quantity of solvent is inappropriate OR
The recrystallisation process is carried out with insufficient care OR
Either the quantity or quality of recrystallised product is inappropriate.

0 marks: At least two of the areas of the task are performed poorly.
The quantity of solvent is inappropriate.
The recrystallisation process is carried out with insufficient care.
Either the quantity or quality of recrystallised product is inappropriate
Test the purity of an organic solid

For example:

Determine the melting point of benzenecarboxylic acid
2 marks: All areas of the task are carried out competently.
The quantity used and the preparation of the solid are appropriate (e.g. dry, powder).
The apparatus set-up is safe and appropriate.
 Heating is carried out with due care and only as long as necessary, giving an accurate value for the melting point.

1 mark: One of the areas of the task is performed poorly.
Either the quantity used or the preparation of the solid is inappropriate OR
The apparatus set-up is unsafe or inappropriate OR
Heating is longer than necessary and the m.p. is inaccurate.

0 marks: At least two of the areas of the task are performed poorly. Either the quantity used or the preparation of the solid is inappropriate. The apparatus set-up is unsafe or inappropriate. Heating is longer than necessary and the m.p. is inaccurate.

Mathematical Requirements

Mathematical requirements

Mathematical requirements

In order to develop their skills, knowledge and understanding in science, candidates need to have been taught, and to have acquired competence in, the appropriate areas of mathematics relevant to the subject as set out below.

Candidates should be able to:

Arithmetic and computation
  • recognise and use expressions in decimal and standard form
  • use ratios, fractions and percentages
  • make estimates of the results of calculations (without using a calculator)
  • use calculators to find and use power, exponential and logarithmic functions ( xn, 1/x, √x, log10x, ex, logex )
Handling data
  • use an appropriate number of significant figures
  • find arithmetic means
  • construct and interpret frequency tables and diagrams, bar charts and histograms
Algebra
  • understand and use the symbols: =, <, <<, >>, >, ∝, ~.
  • change the subject of an equation by manipulation of the terms, including positive, negative, integer and fractional indices
  • substitute numerical values into algebraic equations using appropriate units for physical quantities
  • solve simple algebraic equations
  • use logarithms in relation to quantities that range over several orders of magnitude
Graphs
  • translate information between graphical, numerical and algebraic forms
  • plot two variables from experimental or other data
  • understand that y = mx + c represents a linear relationship
  • determine the slope and intercept of a linear graph
  • calculate rate of change from a graph showing a linear relationship
  • draw and use the slope of a tangent to a curve as a measure of rate of change
Geometry and trigonometry
  • appreciate angles and shapes in regular 2D and 3D structures
  • visualise and represent 2D and 3D forms including two-dimensional representations of 3D objects
  • understand the symmetry of 2D and 3D shapes