IB Chemistry Syllabus Explained: Topics, Assessment and What to Expect

In 2023, the IB substantially reorganised the IB Chemistry syllabus, regrouping familiar chemistry around two big ideas. Students sitting exams from May 2025 onwards are the first to be assessed on it. 

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Here's what that rebuild actually looks like: IB Chemistry is now taught through two organising strands, Structure and Reactivity, each split into three sub-strands covering matter, bonding, periodicity, energetics, reaction rates, equilibrium, and reaction mechanisms, with Higher Level adding extra depth on top.

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In this article, we'll map every strand, show what separates Standard Level from Higher Level, and break down how each paper and the Scientific Investigation are weighted.

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Let's get right into it.

Key takeaways

• IB Chemistry was redesigned for first assessment in May 2025, replacing the old 11-topic model with two organising strands, Structure and Reactivity, each split into three sub-strands.
• Structure covers what matter is made of (particulate nature, bonding, classification), while Reactivity covers how and why reactions happen (energetics, reaction extent, mechanisms), connected by the principle that structure determines reactivity and reactivity transforms structure.
• HL students study 240 teaching hours against SL's 150, covering the same core strands in greater depth plus extra content like entropy, spectroscopy, and Lewis acid-base theory.
• The compulsory experimental programme totals 40 hours at SL and 60 at HL, split between practical work, the Collaborative Sciences Project, and the Scientific Investigation.
• The final grade is split across three components: Paper 1 (36%, multiple-choice and data-based questions), Paper 2 (44%, short-answer and extended-response questions), and the Scientific Investigation (20%, the only internally assessed component).
• IB Chemistry has a reputation as one of the more demanding Group 4 subjects, but understanding how Structure and Reactivity connect makes it far more manageable. 

What is taught in IB Chemistry? The Structure and Reactivity framework

The IB rebuilt Chemistry around two organising concepts for first assessment in May 2025, moving away from 11 separate topics toward a thematic model built on the idea that structure determines reactivity, and reactivity in turn transforms structure.

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Here's how the framework breaks down:

• Structure - the "what things are made of" strand, exploring atomic structure and the particulate nature of matter, how ionic, covalent, and metallic bonding form, and how a substance's makeup shapes its physical and chemical behaviour, including its organic and spectroscopic identity
• Reactivity - the "what things do" strand, working through why chemical reactions happen in the first place, how much product forms and how quickly, how far a reaction proceeds toward equilibrium, and the underlying mechanisms, like proton transfer and redox, that actually drive chemical change

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That deceptively simple two-strand split is what sits behind the dense subtopics most students underestimate, and it's the same framework our IB Chemistry guide walks through in full.

Structure

Structure 1: Models of the particulate nature of matter

This sub-strand opens the course by asking what matter is actually made of, using kinetic molecular theory to explain the physical properties of solids, liquids, and gases through particle motion and energy.

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Here are the specific topics this sub-strand covers:

• Kinetic molecular theory and states of matter - how particle motion and energy explain the properties of solids, liquids, and gases, and how temperature relates to average kinetic energy
• The nuclear atom - protons, neutrons, and electrons, and isotopes, extending at Higher Level to using mass spectra to determine relative atomic mass 
• Electron configurations - energy levels and sublevels (s, p, d, f), and using the Aufbau principle to deduce orbital diagrams and configurations up to Z = 36 
• Counting particles by mass: the mole - using the mole as the standard unit for counting particles in a sample
• Ideal gases - the ideal gas equation, PV = nRT, relating pressure, volume, temperature, and amount of gas

Structure 2: Models of bonding and structure

Diamond and graphite are both pure carbon, yet one is the hardest natural material on Earth and the other conducts electricity and crumbles between your fingers, a contrast that comes down entirely to how their atoms bond together.

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This sub-strand gives you the three models that explain it:

• The ionic model - how electrostatic attraction between oppositely charged ions produces properties like high melting points and electrical conductivity when molten or dissolved
• The covalent model - shared electron pairs, molecular shape and bond polarity using VSEPR theory, extending at Higher Level to hybridisation and delocalisation 
• The metallic model - the "sea of electrons" model and how it explains metallic conductivity, malleability, and ductility
• From models to materials - treating bonding as a continuum, placing materials on the bonding triangle, and using that position to explain the properties of alloys and polymers, including how addition polymers form 

Structure 3: Classification of matter

Structure 3 does something no other sub-strand does: it asks you to classify two completely different kinds of matter, the entire periodic table on one side and every organic molecule you'll ever draw on the other.

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This sub-strand splits into those two areas: 

• The periodic table: classification of elements - properties like ionisation energy, atomic radius, and reactivity change in predictable patterns as you move across a period or down a group
• Functional groups: classification of organic compounds - organic molecules get named, drawn, and classified by the functional groups they contain, including compounds that share a formula but differ in structure

Reactivity

Reactivity 1: What drives chemical reactions?

While Structure explains what a substance is made of, Reactivity turns to what it does, and there's no better place to start than a burning match releasing energy you can feel from across the room, against an ice pack pulling energy in fast enough to sting your skin.

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These three areas cover that difference: 

• Measuring enthalpy change - how heat and temperature differ, and how endothermic and exothermic reactions are identified from energy transfer
• Energy cycles in reactions - using Hess's Law and energy cycles to calculate enthalpy changes that can't be measured directly
• Energy from fuels - the energy released by burning fuels, including fossil fuels and alternatives like biofuels

Reactivity 2: How much, how fast, and how far?

A reaction between the same two chemicals can behave completely differently depending on the question you ask: how much product forms, how quickly it forms, and how far the reaction actually goes before it stops changing.

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This sub-strand answers all three questions in turn:

• The amount of chemical change - stoichiometry, using mole ratios and balanced equations to calculate exactly how much reactant you need and how much product you'll get
• The rate of chemical change - some reactions finish in seconds, others take years, and this covers the collision theory and variables, like temperature and concentration, behind that difference
• The extent of chemical change - reactions don't always finish; many settle into equilibrium, a balance between reactants and products rather than a true endpoint

Reactivity 3: What are the mechanisms of chemical change?

Reactivity 3 covers the four core reaction mechanisms in IB Chemistry: proton transfer, electron transfer, electron sharing, and electron-pair sharing.

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Here's how those four mechanisms break down:

• Proton transfer reactions - acid-base chemistry, defining acids and bases by their ability to donate or accept a proton
• Electron transfer reactions - every battery, every rusting nail, and every combustion reaction comes down to electrons moving from one species to another, tracked through oxidation states
• Electron sharing reactions - this one centres on radicals, species with an unpaired electron that form when a bond breaks evenly (homolytic fission), and the radical substitution reactions they drive in alkanes 
• Electron-pair sharing reactions - nucleophiles and electrophiles, and the nucleophilic substitution and electrophilic addition reactions that explain how one organic molecule turns into another

HL-only content: what's added on top

HL students spend 90 more hours in the classroom than SL students, working through 240 teaching hours against SL's 150, and this section is exactly where that extra time goes.

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Here's where each addition belongs:

• Structure 1 - using mass spectra to determine an element's relative atomic mass from its isotopic composition, plus calculating ionisation energy from the convergence limit of the hydrogen emission spectrum, and using successive ionisation energies to deduce an element's electron configuration 
• Structure 2 - resonance structures, benzene's structure, expanded octets, formal charge, sigma and pi bonds, and hybridisation for a deeper model of covalent bonding, plus transition elements' delocalised d-electrons  and their effect on melting point and conductivity, plus condensation polymers extending the "from models to materials" content
• Structure 3 - deeper transition element chemistry (variable oxidation states, coloured complexes, complex ions) added to the periodic table content, plus stereoisomers and spectroscopy (mass spectrometry, IR, and ¹H NMR interpretation) added to organic classification
• Reactivity 1 - using enthalpy of combustion and formation data (including Born-Haber cycles) in Hess's Law calculations, plus entropy and Gibbs free energy to explain why a reaction happens spontaneously
• Reactivity 2 - multistep reaction mechanisms, deriving rate equations, the rate constant, and the Arrhenius equation for rate of reaction, plus using the reaction quotient and the Gibbs energy-equilibrium constant relationship to quantify how far a reaction proceeds
• Reactivity 3 - pOH, Ka, Kb, and pKa/pKb values, salt hydrolysis, full pH curves and buffer solution calculations for acid-base reactions, plus standard electrode potentials, cell potential, and electrolysis of aqueous solutions for redox reactions, plus Lewis acid-base theory, coordination bonds, and detailed SN1/SN2 and electrophilic substitution mechanisms for electron-pair sharing reactions

The experimental programme

Beyond the six syllabus strands, IB Chemistry includes a compulsory experimental programme that builds the practical skills tested across those topics, worth 40 hours at SL and 60 hours at HL. 

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It splits into three parts: practical work (20 hours SL, 40 hours HL), the Collaborative Sciences Project (10 hours at both levels), and the Scientific Investigation (10 hours at both levels). 

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Practical work builds the lab skills tested in Paper 1B's questions on experimental work. Alongside it sits the Collaborative Sciences Project, an interdisciplinary team task that, unlike the other two components, isn't assessed at all. The final piece is the Scientific Investigation, the only graded component, an open-ended, student-designed investigation reported in up to 3,000 words. 

How is IB Chemistry assessed?

IB Chemistry's final grade comes from three components, and knowing how each is weighted before you sit a single exam changes how you plan your revision time.

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Here's how each one contributes:

• Paper 1 - worth 36% of the final grade, split into Paper 1A (multiple-choice questions) and Paper 1B (data-based questions and questions on experimental work), sat together in one sitting with a calculator and the Chemistry data booklet
• Paper 2 - worth 44% of the final grade, made up of short-answer and extended-response questions, also using a calculator and the data booklet
• Scientific Investigation - worth 20% of the final grade, the only internally assessed component, marked by the teacher and externally moderated by the IB

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Of the three, the Scientific Investigation is the one you have the most control over, since it isn't sat under exam conditions. Our full guide on how to choose an IB Chemistry IA topic walks through picking a research question that plays to your strengths and fits the assessment criteria. 

Is Chemistry hard in IB?

IB Chemistry has a reputation as one of the more demanding Group 4 subjects, largely due to its dense content and heavy calculation load at Higher Level. 

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What makes the course manageable is consistent practice and understanding the Structure-Reactivity links, rather than memorising topics in isolation.

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A syllabus map like this one shows you what's covered, but it can't replicate what it's actually like to work in a real lab, design your own experiment, or get feedback from someone who studies chemistry professionally. 

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That gap between reading a specification and doing real chemistry matters, because it's where curiosity starts to turn into genuine understanding. 

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Closing that gap is what Immerse Education's chemistry programmes are built for. Our Chemistry Summer School runs as a two-week residential programme at Cambridge or Oxford for ages 16 to 18, covering atomic structure, thermodynamics, and bonding theories like Lewis structures, hybridisation, and VSEPR, alongside a personal research project and the option to earn 8 UCAS points. 

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If you'd rather build that depth remotely, our Online Chemistry Summer School is a flexible, self-paced research pathway for ages 13 to 18, developing personal research and study skills alongside chemical bonding, stoichiometry, thermodynamics, and kinetics with 1:1 expert tutoring.

FAQs

What is taught in IB Chemistry?

IB Chemistry is taught through two strands, Structure and Reactivity, covering six sub-strands overall. The 2025 redesign replaced the old 11-topic model, with first assessment in May 2025.

What are the topics covered in the IB Chemistry syllabus?

The syllabus covers atomic structure, bonding, the periodic table, organic classification, energetics, kinetics, equilibrium, and reaction mechanisms. HL studies the same core content in greater depth, plus extra topics like entropy and spectroscopy.

What's the difference between Structure and Reactivity?

Structure covers what a substance is made of; Reactivity covers what it does. The two strands connect throughout the course: structure determines reactivity, and reactivity transforms structure.

Does HL cover extra topics or just go deeper into the same ones?

Both. HL shares SL's core strands but adds new content, like entropy and spectroscopy, on top of greater depth across 240 teaching hours versus SL's 150.

What's in the IB Chemistry Data Booklet?

The Data Booklet contains the periodic table, equations, constants, and reference data specific to the course, provided for every exam paper at both SL and HL.

Is Chemistry hard in IB?

IB Chemistry has a reputation as one of the more demanding Group 4 subjects, largely due to its dense content and calculation load at HL.  Understanding how Structure and Reactivity connect makes it far more manageable.

Conclusion: A map for the whole course

Chemistry rewards students who see the whole picture, not ones who memorise topics in isolation, since Structure and Reactivity connect throughout the entire IB syllabus.

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Whether you're weighing SL against HL, or already deep into Reactivity 3 mechanisms, knowing what's ahead changes how you actually prepare for it.

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The syllabus is the map, but what you do with it determines how confidently you walk into results day itself.

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Ready to go beyond the page? Explore our Chemistry Summer School and take your chemistry further with expert tutors in Cambridge or Oxford.