Physical Sciences Paper 2 (Chemistry): Where the Marks Are

Physical Sciences Paper 2 is the chemistry paper, and for many students it is the paper with more room to improve. Unlike Paper 1 (physics), where misconceptions in mechanics can cascade across the whole paper, Paper 2 has clearer boundaries between sections — which means targeted revision of individual topics can quickly improve your score.

The Topic Breakdown

Paper 2 is 150 marks and covers three broad areas:

1. Matter and materials (~55 marks): Intermolecular forces, states of matter, organic chemistry
2. Chemical change (~55 marks): Energy changes in reactions (thermochemistry), electrochemical cells, equilibrium, acids and bases
3. Chemical systems (~40 marks): The atmosphere and industrial chemistry (Haber process, Contact process)

Understanding this breakdown helps you spot where your mark potential lies. Organic chemistry and electrochemistry together often account for 40–50 marks — these two topics are your highest priorities.

Organic Chemistry: The Biggest Opportunity

Organic chemistry is predictably structured, which makes it highly learnable. The DBE tests:

• Naming organic molecules (IUPAC nomenclature for alkanes, alkenes, alkynes, alcohols, carboxylic acids, esters, haloalkanes)
• Physical properties (boiling points, solubility, and how intermolecular forces explain them)
• Reactions (substitution, addition, elimination, esterification, cracking)
• Isomers (structural isomers and their different properties)

Many students lose marks in organic chemistry through naming errors. Practise writing and naming structural formulas until it is fluent. The DBE gives you marks for the structural formula AND the IUPAC name — get both right and you earn full marks on those sub-questions.

Electrochemistry: High-Value, Highly Doable

Electrochemical cells carry significant marks and follow a predictable pattern every year. Know:

• Galvanic cells: How they generate electricity (spontaneous reaction), anode (oxidation), cathode (reduction), flow of electrons and ions
• Electrolytic cells: How they use electricity to force a non-spontaneous reaction, electrolysis of water, electroplating
• The Table of Standard Reduction Potentials: How to use it to determine spontaneity (E°cell = E°cathode - E°anode), which species is oxidised/reduced
• Writing half-reactions and net ionic equations

The Table of Standard Reduction Potentials is provided in the exam, but students who are unfamiliar with how to use it waste significant time. Practise interpreting it until you can read off values and write equations confidently.

Acids and Bases: Know Your Definitions

The DBE tests multiple acid-base definitions:

• Arrhenius: Acid produces H⁺ in water; base produces OH⁻
• Lowry-Brønsted: Acid is a proton donor; base is a proton acceptor
• Conjugate acid-base pairs

The most common errors: using the wrong definition for the context, and failing to identify conjugate pairs correctly. The exam will specify which theory to use — read the question carefully.

Equilibrium and Le Chatelier's Principle

Equilibrium questions test whether you can predict how a system at equilibrium will respond to changes in concentration, temperature, or pressure. Le Chatelier's Principle states that the system will shift to oppose the change.

These questions are often multi-part: a change is described, you must predict the shift, explain the reasoning, and state how the equilibrium constant (Kc) is affected (it only changes with temperature). Do not confuse shifts in equilibrium with changes in Kc — a pressure or concentration change shifts the equilibrium but does not change Kc.

Practise interpreting equilibrium graphs from past papers. The ability to read and explain what is shown on a concentration-time graph is a regular exam question.

Work through NSC and IEB past papers for Paper 2 at Examslayers to build confidence in each of these sections.