Master IGCSE Chemistry

Cambridge IGCSE Chemistry uses 0620; Cambridge IGCSE (9–1) uses 0971 and follows the same syllabus content with a different grading scale. Pearson Edexcel International GCSE Chemistry linear uses 4CH1. Use your specification as the master checklist because assessment structures differ.

Link particle arrangement, separation, motion and energy to the properties of solids, liquids and gases. When heating, particles gain kinetic energy; do not write only that they ‘move more’.

Diffusion is the net movement of particles from higher to lower concentration due to random particle motion. Temperature affects particle speed, and lighter gas particles generally diffuse faster under comparable conditions.

An element contains one type of atom; a compound contains different elements chemically combined in fixed proportions; a mixture contains substances not chemically combined and can be separated physically.

Know proton number, mass/nucleon number, relative charges and masses of subatomic particles, isotope notation and why isotopes of one element have similar chemical properties.

For the first 20 elements, connect electron arrangement to group, period and ion formation. Use outer electrons to explain trends only where required by your specification.

Construct neutral formulae by balancing total positive and negative charge. Example: Al3+ and O2− combine as Al2O3.

Change coefficients, never subscripts inside a correct formula. Check every element on both sides and add state symbols only when required.

Ionic bonding is the strong electrostatic attraction between oppositely charged ions in a giant ionic lattice. Do not describe ionic bonding as electron sharing.

A covalent bond is a shared pair of electrons between atoms. Draw dot-and-cross diagrams carefully and show the electron information requested.

Describe a lattice of positive metal ions with delocalised electrons and the electrostatic attraction between them.

Identify the particles and forces that must be overcome. Simple molecular substances have relatively weak intermolecular forces; giant structures involve many strong bonds.

Ionic substances conduct when molten or aqueous because ions can move. Metals conduct because delocalised electrons are mobile.

Relate bonding and structure to hardness, conductivity and uses. Graphite has delocalised electrons and layers that can slide.

Add relative atomic masses according to the formula. For isotope questions, use a weighted mean from isotopic abundance.

moles = mass ÷ Mr. Convert the given quantity to moles before using the balanced-equation ratio.

Follow the chain: given quantity → moles → equation ratio → target moles → required quantity.

Compare available amounts with the stoichiometric ratio. The limiting reactant is used up first and determines the maximum product.

For molar concentration use concentration = moles ÷ volume in dm3. Convert cm3 to dm3 by dividing by 1000.

Use the molar gas volume required by your board or provided by the question and pay attention to stated conditions rather than inserting a remembered value automatically.

Convert masses or percentages to moles, divide by the smallest amount, scale to whole-number ratios, then use Mr to move from empirical to molecular formula when required.

% yield = actual ÷ theoretical × 100. % purity = mass of pure substance ÷ total sample mass × 100.

Show the relationship, substitution, units and intermediate working. Keep unrounded calculator values until the final answer and round sensibly.

Cations move to the cathode and anions to the anode. Reduction occurs at the cathode; oxidation occurs at the anode.

Balance atoms first, then balance charge with electrons. Check whether electrons are reactants or products.

Molten electrolytes contain ions from the compound only. Aqueous solutions involve water too, so the discharged products may differ.

Exothermic reactions transfer energy to the surroundings; endothermic reactions take in energy from the surroundings.

A catalyst lowers activation energy but does not change the overall energy change of the reaction.

Energy change is approximated by energy required to break bonds minus energy released when new bonds form.

Successful reactions require collisions with sufficient energy. Explain how temperature, concentration, gas pressure, surface area and catalysts change collision frequency or the fraction of successful collisions.

Average rate is change in quantity divided by time. Pearson explicitly expects candidates to understand the gradient of a tangent as a measure of instantaneous rate of change.

Learn the exact equilibrium requirements for your board. At dynamic equilibrium in a closed system, forward and reverse reaction rates are equal.

Use oxygen transfer, electron transfer or oxidation state as required by the context. In electron terms: oxidation is loss, reduction is gain.

An alkali is a soluble base. Use the exact acid–base definitions required by your syllabus and do not confuse neutralisation with dilution.

Know the direction of acidity and alkalinity and use litmus or universal indicator appropriately.

The method depends on solubility and reactants: excess insoluble solid with acid, acid–alkali titration, or precipitation are common routes.

Use a volumetric pipette for a fixed accurate volume and a burette for a measured variable volume. Record readings consistently and use an indicator where appropriate.

Filtration separates an insoluble solid; crystallisation obtains a soluble solid; simple/fractional distillation use boiling-point differences; chromatography separates dissolved substances.

Use spot patterns to identify mixtures and, where required, calculate Rf = distance moved by substance ÷ distance moved by solvent front.

Hydrogen gives a pop with a lighted splint; oxygen relights a glowing splint; carbon dioxide turns limewater milky; ammonia turns damp red litmus blue; chlorine bleaches damp litmus. Cambridge also specifies sulfur dioxide decolourising acidified potassium manganate(VII).

For current Cambridge 0620: Li+ red, Na+ yellow, K+ lilac, Ca2+ orange-red, Ba2+ light green, Cu2+ blue-green. Check your own board list before memorising.

Learn the required cation and anion tests for your board. Record reagent, condition and observation, including precipitate colour and solubility in excess reagent where relevant. Cambridge provides qualitative-analysis notes in Papers 5 and 6, but interpretation still matters.

Connect group number, outer electrons and chemical behaviour. Use period number to relate to occupied shells where your board uses this model.

Group 1 reactivity increases down the group; Group 7 reactivity decreases down the group. Link trends to electron arrangements where required.

A more reactive metal displaces a less reactive metal from its compound; a more reactive halogen displaces a less reactive halide from solution.

Common syllabus ideas include variable oxidation states, coloured compounds and catalytic activity; use only the examples required by your specification.

Apply relative reactivity to water/steam, dilute acids and displacement reactions. More reactive metals generally require electrolysis for extraction; less reactive metals may be reduced chemically.

Rusting of iron requires oxygen and water. Explain barrier protection or sacrificial protection by the process it prevents or redirects.

Study the board-specific causes, effects and controls of pollutants, water treatment and atmospheric chemistry. Base explanations on chemical reactions and evidence.

Recognise required functional groups, general formulae, names and structural/displayed formulae. Requirements differ between boards.

Relate single C–C bonds to saturation and learn required combustion and substitution chemistry.

Alkenes are unsaturated and undergo addition reactions. Bromine water is commonly used to test for unsaturation.

Distinguish fermentation and hydration routes where required, including specified conditions and advantages/disadvantages.

Use the –COOH functional group and connect its acidic behaviour to reactions specified by your syllabus.

Addition polymerisation opens C=C bonds with no small molecule eliminated. Condensation requirements vary by board, so follow your exact specification.

Choose apparatus to suit the measurement. Burettes and volumetric pipettes give more precise volume measurements than routine measuring cylinders.

State exactly what is changed, what is measured and what must be controlled for a fair test.

Use a range broad enough to reveal a trend and enough values to support a graph or conclusion.

Repeat measurements, identify anomalies only with evidence and calculate a mean from suitable results.

Name the equipment or procedural change and explain how it reduces uncertainty or controls a variable; avoid vague phrases like ‘be more accurate’.

Match the precaution to the hazard. For example, corrosive or irritant chemicals justify eye protection and careful handling.

Observation: colour change, precipitate, gas, temperature change. Inference: what species or process the observation suggests.

Put the independent variable first, units in headings, consistent precision in measurements, and sensible graph scales with labelled axes.

Identify limitations, explain their effect, distinguish random variation from systematic error when appropriate, and suggest a specific improvement.

Cambridge explicitly expects experimental skills to be applied in unfamiliar situations. Read the apparatus and data, then apply the underlying principle.

Cambridge 0620 currently includes command words such as analyse, calculate, compare, contrast, deduce, define and describe; Pearson publishes its own command-word taxonomy. Learn your board’s meanings.

Describe states what happens or the pattern shown. Explain gives the scientific reason or mechanism.

Use paired comparison statements instead of two separate descriptions.

When a graph or table is supplied, quote relevant values with units to support trends and conclusions.

Identify the principle first—particles, bonding, redox, stoichiometry, rate, equilibrium or practical design—then apply it logically.

Start with topic practice, then mixed questions, then complete papers under timed conditions.

Identify the missing scientific idea, not only the missing phrase. Keep a mistake log for recurring errors.

Flashcards work well for tests, definitions, conditions, colours, formulae and trends; calculations need worked practice too.

Short daily practice with balancing, ionic equations and half-equations improves speed and accuracy.

Check formulae, charge, balancing, units, state symbols, significant figures, graph labels and whether the conclusion is supported by the evidence.