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GCSEOCR

Chemistry

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Solids, liquids and gases in the particle model

The particle model

Particle arrangement, movement and energy in each state

The particle model

Melting and freezing explained by particles

The particle model

Boiling and condensing explained by particles

The particle model

Sublimation and deposition explained by particles

The particle model

Changes of state are physical and reversible

The particle model

Curriculum Modules

Solids, liquids and gases in the particle model Particle arrangement, movement and energy in each state Melting and freezing explained by particles Boiling and condensing explained by particles Sublimation and deposition explained by particles Changes of state are physical and reversible Diffusion in gases using the particle model Diffusion in liquids using the particle model Explaining gas pressure using particle collisions Physical changes vs chemical changes (particle-level view)Why the “hard sphere” particle model has limitations Particle model limitations: forces, spacing and particle size

Dalton’s atomic model Thomson’s plum pudding model Rutherford/Geiger–Marsden alpha scattering experiment The nuclear model: what it explained and what it didn’t Bohr’s electron shell model Why atomic models change over time (evidence and revision)Nucleus vs electron cloud: where mass and charge are Orders of magnitude: typical atom size (10⁻¹⁰ m)Proton, neutron, electron: charges and relative masses Atomic number and mass number Isotopes and isotope notation Calculating protons, neutrons and electrons in atoms Ions: what changes when ions form Calculating protons, neutrons and electrons in ions

“Pure” in chemistry vs “pure” in everyday language Elements, compounds and mixtures: what counts as pure Using melting point to identify purity Why impurities change melting point (range + lower mp)Relative atomic, molecular and formula mass Calculating relative formula mass from a formula Using relative masses inside balanced equations Empirical formula from atom ratios Empirical formula from models/diagrams Formulations as useful mixtures Alloys as formulations (why alloys are useful)Filtration: separating insoluble solids from liquids Crystallisation: making a solid from solution Simple distillation: separating a solvent from a solution Fractional distillation: separating liquids with different boiling points Choosing separation methods from substance properties Paper chromatography: setup and how separation happens TLC chromatography: setup and spotting Mobile phase vs stationary phase Interpreting a chromatogram (spots, components)Calculating and comparing Rf values Using chromatography to test purity Choosing chromatography methods (paper/TLC/gas) for context

Metals vs non-metals: key physical properties Metals vs non-metals: chemical behaviour (ions/oxides)Electron shells and the periodic table (group/period meaning)Atomic number and electron arrangement link Ionic bonding: electron transfer and ion formation Ionic lattices: why ionic compounds aren’t “molecules”Covalent bonding: sharing electrons in molecules Metallic bonding: positive ions and delocalised electrons Polymers as giant molecules (repeat units idea)Giant covalent vs simple molecular substances Dot-and-cross diagrams for simple covalent molecules Dot-and-cross diagrams for binary ionic compounds From ion charges to ionic formulae (criss-cross method)Comparing bonding/structure types across substances Representations and models: strengths and limitations 2D vs 3D structures (why shape matters)Mendeleev’s table: what he got right (patterns)Modern periodic table: why atomic number matters

Carbon’s four covalent bonds: why it matters Carbon chains and rings: many organic compounds Diamond structure and key properties Graphite structure and key properties Graphene structure and key properties Fullerenes structure and key properties Bond strength vs intermolecular forces (what each controls)Explaining mp/bp using bonds and intermolecular forces Using data to predict state at given conditions Ionic solids: structure and properties (mp, conductivity)Simple molecular substances: structure and properties Giant covalent substances: structure and properties Metals: structure and properties (conductivity, malleability)Polymers: structure and properties (flexibility, melting range)Nanoparticles: size and scale (standard form focus)Surface area to volume ratio at the nanoscale Uses of nanoparticles (properties-led examples)Risks/uncertainties of nanoparticles (size changes behaviour)

Using symbols to write formulae for elements Writing formulae for simple covalent compounds Writing formulae for ionic compounds (from charges)Writing balanced symbol equations from word equations Using conservation of mass to balance equations State symbols: (s), (l), (g), (aq)Half equations: what they represent Writing half equations for simple processes Common ions: recognising and using ion formulae Deducing compound formulae from ions in a question Writing balanced ionic equations (cancel spectator ions)Avogadro constant: meaning (standard form)The mole: what it measures Converting mass to moles (and back)Conservation of mass in reactions Explaining mass change in open systems (gas exchange)Stoichiometry from a balanced equation (mole ratio)Limiting reactant: identifying what runs out first Calculating masses from equations

Exothermic reactions: temperature rise of surroundings Endothermic reactions: temperature fall of surroundings Energy transfer vs “energy used up” (correct language)Reaction profiles: exothermic vs endothermic Activation energy on a reaction profile Bond breaking needs energy (endothermic step)Bond making releases energy (exothermic step)Overall energy change: making minus breaking Bond energy calculations for reaction energy change (Higher)Comparing reactions using reaction profiles

Oxidation and reduction in terms of oxygen Identifying oxidised and reduced species (oxygen definition)Oxidising agents and reducing agents (oxygen definition)Oxidation and reduction in terms of electrons Identifying oxidised and reduced species (electron definition)Acids in water: hydrogen ions Alkalis in water: hydroxide ions Neutralisation: acid + alkali/base → salt + water Ionic equation for neutralisation: H⁺ + OH⁻ → H₂O Acids + metals: predicting products and balancing equations Acids + carbonates: predicting products and balancing equations Concentrated vs dilute acids (amount per volume)Strong vs weak acids (degree of ionisation)pH scale: what it measures Neutrality, acidity and alkalinity (whole-number pH)pH and [H⁺]: factor of ten rule Measuring pH with indicators (universal indicator)Measuring pH with a pH probe/meter

Electrolytes, ions, and why ionic liquids conduct Cations and anions: direction of movement Cathode and anode: identifying each electrode Products with inert electrodes (metals/H₂ at cathode; non-metals at anode)Molten binary ionic electrolysis: predicting products Aqueous electrolysis: competing species idea Products for aqueous NaCl (brine) electrolysis Products for aqueous CuSO₄ electrolysis (inert electrodes)Explaining products using ions present and discharge competition Writing half equations for electrode reactions Electrolysis and redox (electron gain/loss at electrodes)

Group 1: key physical and chemical properties Group 1 trends down the group (reactivity pattern)Group 7: key physical and chemical properties Group 7 trends down the group (reactivity pattern)Group 0: key physical and chemical properties (inert behaviour)Group 0 trends down the group (bp/density patterns)Explaining group trends using outer-shell electrons Transition metals: general properties (density, mp, reactivity)Transition metal ions: coloured compounds and variable charges Transition metals as catalysts (why useful)Predicting reactivity from periodic table position Metal + water reactions: patterns and predictions Metal + dilute acid reactions: patterns and predictions Reactivity series: what it is and how it’s used Displacement reactions between metals and metal salts Using experiments to deduce metal reactivity order

Testing oxygen (positive test + why it works)Testing hydrogen (positive test + why it works)Testing carbon dioxide (positive test + why it works)Testing chlorine (positive test + why it works)Testing carbonate ions (acid test + CO₂ confirmation)Halide tests with silver nitrate (Cl⁻, Br⁻, I⁻)Sulfate test with barium ions NaOH cation tests: calcium NaOH cation tests: copper NaOH cation tests: iron(II)NaOH cation tests: iron(III)NaOH cation tests: zinc (including solubility points)Flame tests: method and safety Flame colours: Li⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺Identifying unknowns from multiple test results Instrumental methods: speed, accuracy, sensitivity Interpreting instrumental results using references Reading simple mass spectrometry-style charts (pattern matching)

Concentration in mol/dm³: what it means Calculating mol/dm³ from mass, formula mass, and volume Converting volume units (cm³ ↔ dm³)Concentration in g/dm³: meaning and use Preparing a standard solution (core technique)Titration apparatus and setup (burette, pipette, indicator)Identifying the end point (colour change judgement)Titration calculations using mole ratios Gas moles and gas volume relationship Molar gas volume at RTP (24 dm³): correct use Calculating gas volumes from a balanced equation Theoretical yield from reactant mass Actual yield vs theoretical yield Percentage yield calculations Atom economy: definition Atom economy calculations from equations Choosing pathways using data (yield, atom economy, rate, eqm, by-products)

Rate of reaction: what it measures Collision theory basics (frequency and energy)Measuring rate by gas volume collected Measuring rate by mass loss Measuring rate by precipitation (visibility)Measuring rate by colour change/time Plotting rate graphs correctly (units and axes)Interpreting rate graphs (steepness and completion)Mean rate over an interval Instantaneous rate using tangents/gradients (Higher)Effect of concentration on rate (collision theory)Effect of temperature on rate (collision theory)Effect of surface area on rate (collision theory)Effect of pressure on gas reactions (collision theory)Catalysts: what they do and don’t do Catalysts and activation energy (reaction profile view)Designing a fair test for rate (controls and repeats)

Reversible reactions: symbol and meaning Closed systems and why they matter for equilibrium Dynamic equilibrium: forward rate equals reverse rate Le Chatelier: changing concentration Le Chatelier: changing temperature Le Chatelier: changing pressure (gas equilibria)Using equilibrium shifts to increase yield “Best conditions” problems: yield vs rate vs cost trade-offs

Using carbon to extract metals (reduction of oxides)Extracting iron: principles (carbon in reactivity series)Extracting non-ferrous metals by reduction (principles + example)Why some metals must be extracted by electrolysis Electrolysis extraction: basic industrial principles Bioleaching: how bacteria help metal extraction Phytomining: using plants to accumulate metals Comparing biological and traditional extraction methods Haber process: reactants and products Haber process: catalyst and conditions Haber process: equilibrium (yield vs rate trade-off)Why the Haber process matters for food production NPK fertilisers: what N, P and K do for crops Fertiliser production as integrated industrial processes Making fertilisers in lab vs industry Contact process: why we make sulfuric acid Contact process: steps, catalyst and conditions Contact process: equilibrium (yield vs rate trade-off)Graphs of conditions vs rate (industry context)Choosing industrial conditions using cost, energy, eqm and rate Life-cycle assessment: included stages Using LCA data to make a judgement Recycling for a different use (why viable)Factors affecting recycling decisions (economic + environmental)Key alloys: steel, brass, bronze, solder, duralumin Corrosion: what it is and when it happens Rusting conditions for iron (water + oxygen)Preventing corrosion using barriers (paint/oil/plastic)Preventing corrosion using galvanising/plating Preventing corrosion using sacrificial protection

Functional groups: spotting in structures Homologous series: what makes a family Alkanes: names and displayed structures (first four)Alkenes: names and displayed structures (first four)Alcohols: names and displayed structures (first four)Carboxylic acids: names and displayed structures (first four)Predicting formulas/structures in a homologous series Hydrocarbon combustion: products and equations Bromine test for alkenes (addition across C=C)Hydrogenation of alkenes (addition across C=C)Oxidising alcohols to carboxylic acids (KMnO₄ idea)Addition polymerisation: monomer to polymer (repeat units)Drawing repeat units with [ ]ₙ notation Deducing the monomer from an addition polymer Condensation polymerisation: small molecule loss Polyesters and polyamides as condensation polymers (block diagrams)Making condensation polymer in lab (e.g. nylon practical)DNA: polymer of nucleotides (names of nucleotides)Natural polymers: sugars and amino acids (examples)Functional groups: why reactions can be predicted Fractional distillation of crude oil: how it works Naming crude oil fractions (core set)Fraction boiling points: size + intermolecular forces Crude oil fractions as alkane mixtures (CnH2n+2)Crude oil as finite petrochemical feedstock Modern dependence on hydrocarbons (case examples)Cracking: why we do it (demand vs supply)Cracking conditions (overview)Useful cracking products (alkenes and fuels)Chemical cells: why they produce a potential difference Hydrogen–oxygen fuel cell chemistry (overall reaction)Fuel cells: pros and cons for given uses

Evidence for early atmosphere formation How atmospheric composition changed over time How an oxygen-rich atmosphere developed Greenhouse effect: radiation interacting with atmosphere Evidence for human causes of climate change (correlations)Uncertainties in climate evidence (meaning of uncertainty)Effects of increased CO₂ and CH₄ on climate Mitigating climate change (strategies and trade-offs)Major CO sources and why CO is harmful Major SO₂ sources and why SO₂ is harmful Major NOx sources and why NOx are harmful Particulates: sources and health/environment effects Potable water: meaning Fresh water treatment (filtration/chlorination overview)Treating wastewater: what needs removing Desalination: technique and energy/cost trade-offs

Lab safety basics: hazards, risks and control measures Writing a simple method that controls variables Variables: independent, dependent, control Accuracy, precision, repeatability, reproducibility Recording results in tables with correct units Choosing equipment to reduce uncertainty Drawing and interpreting line graphs for chemistry data Calculating gradients and using them as rates Significant figures in chemistry calculations Scientific diagrams: clear apparatus

Planning a metals reactivity investigation Using observations to rank metals by reactivity Displacement reactions: comparative evidence Writing conclusions that match evidence

Setting up an electrolysis circuit safely Identifying products at electrodes from observations Using ion ideas to explain products

Setting up paper/TLC chromatography correctly Using Rf values to compare samples Using chromatography to assess purity

Filtration and crystallisation in practice Simple distillation in practice Choosing a separation route for a mixture

NaOH tests for cations: safe and systematic AgNO₃ tests for halides: safe and systematic Ba²⁺ tests for sulfate: safe and systematic Using results to identify an unknown sample

Carrying out a titration with consistent technique Getting concordant results and justifying reliability Using titration results for calculations

Making a soluble salt by neutralisation and crystallisation Making an insoluble salt by precipitation and filtration Drying and obtaining a pure, dry sample

Measuring rate by gas collection or mass loss Designing a rates investigation (one factor at a time)Presenting and analysing rates data (graphs and gradients)

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States of Matter and the Particle Model

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