Cambridge International AS & A Level Chemistry (9701) Comprehensive Study Notes

Syllabus Information and Availability

• The syllabus applies to the Cambridge International $AS$ & $A$ Level Chemistry, code $9701$, for examinations in $2025$, $2026$, and $2027$.
• Exam series are held in June and November globally. In India, exams are also available in the March series for $2025$, $2026$, and $2027$.
• Version $1$ of this syllabus was published in September $2022$.
• Schools have the flexibility to shape the curriculum to meet student needs, emphasizing curiosity and a passion for learning.

Educational Aims and Learner Profile

• Aims of the Course:
  • Acquisition of knowledge and understanding and development of practical skills, including efficient, accurate, and safe scientific practices.
  • Learning to apply the scientific method while recognizing the limitations of scientific theories and models.
  • Developing data analysis, evaluation, and conclusion-drawing skills.
  • Cultivating scientific communication using appropriate terminology and conventions.
  • Understanding social, environmental, and economic responsibilities.
• Cambridge Learner Profile: Learners are encouraged to be:
  • Confident: Secure in knowledge and able to communicate through the language of science.
  • Responsible: Practicing safe science and working collaboratively.
  • Reflective: Using evidence to draw informed conclusions.
  • Innovative: Applying problem-solving to novel situations.
  • Engaged: Applying scientific skills in everyday life.

Key Concepts in Chemistry

• Atoms and Forces: Matter consists of atoms interacting through electrostatic forces. The structure of matter determines physical and chemical properties and reactivity.
• Experiments and Evidence: Models and theories are built and tested using evidence from observations and experimental data.
• Patterns in Chemical Behaviour: Predictable patterns in reactivity allow for the design of new substances and synthetic routes.
• Chemical Bonds: Understanding the formation and breaking of bonds via electron movement predicted reactivity and material properties.
• Energy Changes: Enthalpy changes predict the extent, feasibility, and rate of reactions.

Assessment Overview and Weightings

• Paper 1: Multiple Choice ($1$ hour $15$ minutes, $40$ marks): $40$ questions on $AS$ Level content. Weighted at $31\%$ of $AS$ and $15.5\%$ of $A$ Level.
• Paper 2: AS Level Structured Questions ($1$ hour $15$ minutes, $60$ marks): Structured questions on $AS$ Level content. Weighted at $46\%$ of $AS$ and $23\%$ of $A$ Level.
• Paper 3: Advanced Practical Skills ($2$ hours, $40$ marks): Laboratory-based test of experimental skills. Weighted at $23\%$ of $AS$ and $11.5\%$ of $A$ Level.
• Paper 4: A Level Structured Questions ($2$ hours, $100$ marks): Structured questions focusing on $A$ Level content but requiring $AS$ knowledge. Weighted at $38.5\%$ of $A$ Level.
• Paper 5: Planning, Analysis and Evaluation ($1$ hour $15$ minutes, $30$ marks): Written paper on experimental skills. Weighted at $11.5\%$ of $A$ Level.
• Assessment Objectives (AO):
  • AO1: Knowledge and Understanding ($40\%$ weighting).
  • AO2: Handling, Applying and Evaluating Information ($40\%$ weighting).
  • AO3: Experimental Skills and Investigations ($20\%$ weighting).

AS Level Subject Content

1. Atomic Structure

• Particles: Atoms have a small, dense nucleus (protons and neutrons) with electrons in shells.
• Relative Masses and Charges:
  • Proton: Mass = $1.0$, Charge = $+1$.
  • Neutron: Mass = $1.0$, Charge = $0$.
  • Electron: Mass = $\frac{1}{1836}$, Charge = $-1$.
• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons. They share chemical properties but differ in physical properties like mass and density.
• Atomic Orbitals: $s, p, d$ sub-shells. One $s$ orbital ($2$ electrons), three $p$ orbitals ($6$ electrons), five $d$ orbitals ($10$ electrons).
• Ionisation Energy: Defined as the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous $+1$ ions.

2. Atoms, Molecules and Stoichiometry

• Unified Atomic Mass Unit: Defined as $\frac{1}{12}$ of the mass of a carbon-$12$ atom.
• Mole: Measured in terms of the Avogadro constant ($6.022 \times 10^{23}$).
• Formulas: Empirical (simplest ratio) and molecular (actual number).
• Reacting Masses: Calculations involve percentage yield, gas volumes ($V_m = 24.0\,dm^3\,mol^{-1}$ at room conditions), and titration data.

3. Chemical Bonding

• Ionic Bonding: Electrostatic attraction between cations and anions.
• Covalent Bonding: Electrostatic attraction between nuclei and shared pairs of electrons. Includes $\sigma$ (direct overlap) and $\pi$ (sideways overlap) bonds.
• Electronegativity: Power of an atom to attract electrons in a covalent bond.
• VSEPR Theory shapes:
  • $BF_3$: Trigonal planar ($120^{\circ}$).
  • $CH_4$: Tetrahedral ($109.5^{\circ}$).
  • $NH_3$: Pyramidal ($107^{\circ}$).
  • $H_2O$: Non-linear ($104.5^{\circ}$).
  • $SF_6$: Octahedral ($90^{\circ}$).
• Hydrogen Bonding: Occurs in molecules with $N-H$ or $O-H$ groups. Explains anomalous properties of water (density of ice, high boiling point).

4. States of Matter

• Ideal Gas Equation: $pV = nRT$. Assumptions: Zero particle volume and no intermolecular forces.
• Lattices: Giant ionic ($NaCl$), Simple molecular ($I_2$, $C_{60}$), Giant molecular ($SiO_2$, graphite, diamond), and Giant metallic ($Cu$).

5. Chemical Energetics

• Definitions: Enthalpy of reaction ($\Delta H_r$), formation ($\Delta H_f$), combustion ($\Delta H_c$), and neutralisation ($\Delta H_{neut}$).
• Standard Conditions: $298\,K$ and $101\,kPa$.
• Hess’s Law: The enthalpy change for a reaction is independent of the route taken.

7. Equilibria

• Le Chatelier’s Principle: If a system at equilibrium is disturbed, the equilibrium shifts to minimize the change.
• Equilibrium Constants: $K_c$ (concentration) and $K_p$ (partial pressure).
• Acids and Bases: Brønsted–Lowry theory (acids are proton donors, bases are proton acceptors).

A Level Subject Content (Additional Topics)

23. Chemical Energetics (A Level portion)

• Lattice Energy ($\Delta H_{latt}$): Change from gas phase ions to solid lattice. Affected by ionic charge and radius.
• Entropy ($S$): Number of possible arrangements of particles and energy.
• Gibbs Free Energy: $\Delta G^{\ominus} = \Delta H^{\ominus} - T\Delta S^{\ominus}$. A negative $\Delta G$ indicates feasibility.

24. Electrochemistry

• Electrolysis: Calculating charge ($Q = It$) and Avogadro constant ($F = Le$).
• Nernst Equation: $E = E^{\ominus} + (\frac{0.059}{z})\log(\frac{[\text{oxidised species}]}{[\text{reduced species}]})$.

26. Reaction Kinetics

• Rate Equations: $\text{Rate} = k[A]^m[B]^n$.
• Order of Reaction: $m$ and $n$ represent the order with respect to specific reactants.
• Half-life ($t_{1/2}$): For first-order reactions, $k = \frac{0.693}{t_{1/2}}$.

28. Chemistry of Transition Elements

• Definition: $d$-block elements forming stable ions with incomplete $d$ orbitals.
• Properties: Variable oxidation states, catalytic behavior, complex ion formation, and colored compounds.
• Ligands: Monodentate ($H_2O, NH_3, Cl^{-}$), Bidentate (1,2-diaminoethane), Polydentate ($EDTA^{4-}$).
• Crystal Field Theory: Splitting of $d$ orbitals into non-degenerate sets (octahedral or tetrahedral) allows electron promotion by absorbing light of specific frequencies ($\Delta E = hf$).

Organic Chemistry Overview

Functional Groups and Nomenclature

• Alkanes: Hydrocarbons with single bonds.
• Alkenes: $C=C$ bond.
• Halogenoalkanes: $R-X$ (Primary, Secondary, Tertiary).
• Phenols (A Level only): Benzene ring with an $-OH$ group.
• Acyl Chlorides: $R-COCl$.
• Amides: $R-CONH_2$.
• Amino Acids: Feature both amine and carboxyl groups; form zwitterions at the isoelectric point.

Organic Mechanisms

• Free-radical substitution: Initiation, propagation, and termination steps (e.g., alkanes + $Cl_2$ + UV light).
• Electrophilic addition: Markovnikov’s rule applied to alkenes.
• Nucleophilic substitution: $S_N 1$ (unimolecular) and $S_N 2$ (bimolecular).
• Electrophilic substitution: Specifically for arenes (e.g., nitration of benzene with $HNO_3/H_2SO_4$).
• Addition-Elimination: Mechanism for acyl chlorides reacting with water or alcohols.

Analytical Techniques

• Infrared (IR) Spectroscopy: Identifies functional groups based on absorption frequencies (e.g., $C=O$ at $1640\text{--}1750\,cm^{-1}$, $O-H$ carboxyl at $2500\text{--}3000\,cm^{-1}$).
• Mass Spectrometry: Determines relative molecular mass ($M^+$ peak) and calculates carbon atom count via the $[M+1]^+$ peak.
• Chromatography (A Level): Includes Thin-layer ($R_f$ values) and Gas/Liquid chromatography (retention times and percentage composition).
• Carbon-13 NMR: Environments of carbon atoms.
• Proton ($^{1}H$) NMR: Chemical shifts (relative to $TMS$), relative peak areas, and splitting patterns (using the $n+1$ rule).

Practical Assessment Details

Paper 3 (Advanced Practical Skills)

• Manipulation: Setting up apparatus, following instructions, and making measurements (Burette to $0.05\,cm^3$, Thermometer to $0.5^{\circ}C$).
• Presentation: Recording raw data to consistent precision and drawing best-fit lines on graphs.
• Analysis: Calculating gradients, extrapolating data, and identifying errors.
• Quantitative Analysis: Titrations (acid-base, manganate(VII), thiosulfate), rates of reaction, and gravimetric tests.
• Qualitative Analysis: Testing for cations (using $NaOH$ and $NH_3$), anions ($CO_3^{2-}, Cl^-, Br^-, I^-, NO_3^-, SO_4^{2-}$), and gases ($NH_3, CO_2, H_2, O_2$).

Paper 5 (Planning, Analysis and Evaluation)

• Defining the Problem: Identifying independent/dependent variables, risks, and goals.
• Methodology: Describing experimental steps, control experiments, and safety precautions (e.g., fume hoods).
• Evaluation: Identifying anomalous data points and assessing the reliability/validity of investigations.

Data and Constants Table

• Molar gas constant ($R$): $8.31\,J\,K^{-1}\,mol^{-1}$.
• Faraday constant ($F$): $9.65 \times 10^4\,C\,mol^{-1}$.
• Avogadro constant ($L$): $6.022 \times 10^{23}\,mol^{-1}$.
• Electronic charge ($e$): $-1.60 \times 10^{-19}\,C$.
• Ionic product of water ($K_w$): $1.00 \times 10^{-14}\,mol^2\,dm^{-6}$ at $298\,K$.
• Specific heat capacity of water ($c$): $4.18\,kJ\,kg^{-1}\,K^{-1}$.