Upper Secondary
Chemistry

Chemistry can feel abstract at first — with its symbols, equations, and microscopic ideas — but with the right support, it becomes clear and even intuitive. At Inflex, we guide students through core topics like atomic structure, chemical bonding, acids and bases, and organic chemistry using visuals, experiments, and structured practice. Whether a student is aiming to improve their fundamentals or push for distinction, we make Chemistry relatable, manageable, and exam-ready.

Our Approach

Our Chemistry philosophy

Many students see Chemistry as a subject full of equations and facts — but at its core, it's about patterns, cause and effect, and understanding how substances interact. At Inflex, we break down complex topics like mole calculations, redox reactions, and organic chemistry into simple, visual explanations that make sense. We know where students typically struggle — from balancing equations to grasping chemical bonding — and we guide them patiently, step by step. Beyond the exam syllabus, we also show how Chemistry plays a key role in real-world issues like climate change, clean energy, and sustainability. Our goal is to help students move from memorising to truly understanding — and to see Chemistry as a subject with real impact.

subject

Understanding Over Memorisation

We focus on helping students grasp the “why” behind chemical reactions and equations, not just blindly memorising.

Thinking Like a Chemist

We teach students to observe, predict, and explain — just like scientists do — so they can approach questions with logic and confidence.

Application Matters

Whether in practicals or structured questions, we emphasise applying knowledge to real scenarios and exam contexts.

Comprehensive Curriculum

Chemistry Syllabus

Matter - Structures and Properties

Understand how matter behaves by studying particles, states, and bonding. Build strong foundational knowledge crucial for mastering chemistry at the O-Level.

Experimental Chemistry

Explore basic laboratory concepts and techniques such as filtration, crystallisation, and chromatography. Understand how mixtures are separated and how measurement errors can be avoided.

Formulas
Retention Factor (RfR_f value)
Rf=distance travelled by substancedistance travelled by solventR_f = \dfrac{\text{distance travelled by substance}}{\text{distance travelled by solvent}}
The ratio of the distance travelled by a substance to the distance travelled by the solvent.
Definitions
Meniscus
A meniscus is the curve formed at the surface of the liquid in a container.
Parallax Error
The error in measurement that occurs when the observer's eye is not at the same level as the meniscus of the measuring instrument.
Pure Substance
A pure substance is made up of only one type of element or compound and has a specific melting and/or boiling point under fixed conditions.
Mixture
A combination of two or more substances that are not chemically combined and can be separated by physical methods.
Physical Method
A technique used to separate mixtures without changing the chemical composition of the substances.
Residue
The solid that remains on the filter paper after filtration.
Filtrate
The liquid that passes through the filter paper during filtration.
Solubility
The ability of a solute to dissolve in a solvent.
Solvent
The substance that dissolves the solute.
Solute
The substance that is dissolved in a solvent.
Saturated Solution
A solution where no more solute can dissolve in it at a given temperature.
Sublimation
The process where a solid changes into a gas without becoming a liquid.
Crystallisation
A method used to form pure solid crystals from a solution.
Volatile
A substance that evaporates easily at room temperature.
Distillate
The pure liquid collected after distillation.
Miscible
Liquids that form a uniform (homogenous) solution when mixed together.
Immiscible
Liquids that do not mix to form a uniform solution and instead separate into distinct layers when left undisturbed.
Homogeneous Solution
A mixture that has a uniform composition.
Heterogeneous Solution
A mixture that has a non-uniform composition separates into layers when left undisturbed.

The Particulate Nature of Matter

Learn how matter is made up of particles in constant motion. Understand key changes of state and how particle behavior explains diffusion, evaporation, and other physical processes.

Definitions
Matter
Matter is anything that has mass and occupies space.
Kinetic Particle Theory
The kinetic particle theory states that all matter is made up of many tiny particles and these particles are in constant random motion.
Exothermic
A process where energy is given out to the surroundings.
Endothermic
A process where energy is taken in from the surroundings.
Boiling
The process where a liquid changes into a gas.
Condensation
The process where a gas changes into a liquid.
Melting
The process where a solid changes into a liquid.
Freezing
The process where a liquid changes into a solid.
Sublimation
The process where a solid changes into a gas without becoming a liquid.
Vapour Deposition
The process where a gas changes into a solid without becoming a liquid.
Evaporation
The process where a liquid changes into a gas. It takes place at the surface of a liquid at any temperature below the boiling point of the substance.
Diffusion
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.
Atom
An atom is the smallest particle of an element that still has the chemical characteristics of that element.
Proton Number/Atomic Number
The number of protons in the nucleus of an atom.
Nucleon Number/Mass Number
The total number of protons and neutrons in the nucleus of an atom.
Ion
An ion is the particle formed when an atom or group of atoms gains or loses electron(s), but the number of protons and neutrons remains the same.
Cation
A cation is a positively charged ion formed when an atom loses one or more electrons.
Anion
An anion is a negatively charged ion formed when an atom gains one or more electrons.
Isotopes
Isotopes are atoms of the same element that have the same proton number but different nucleon number.
Valence Shell
The valence shell is the electron shell of an atom that is furthest from the nucleus.
Valence Electrons
Electrons in the valence shell.
Stable Electronic Configuration
An atom achieves stable electronic configuration when its valence shell is completely filled with electrons.
Valency
Valency is the number of electrons that must be lost, gained or shared for the atom to attain a noble gas electronic configuration.

Chemical Bonding and Structure

Master how atoms bond to form elements, compounds, and mixtures. Learn to distinguish between ionic, covalent, and metallic bonding, and how structure affects physical properties.

Definitions
Monoatomic Elements
Elements that exist as uncombined atoms.
Diatomic Molecules
Molecules that exist as two chemically combined atoms.
Polyatomic Molecules
Molecules that exist as three or more chemically combined atoms.
Ionic Bonds
The strong electrostatic forces of attraction between positively charged ions and negatively charged ions.
Ionic Bonding
The transfer of electrons from one atom to another.
Ionic Compound
A neutral substance that consists of ions of opposite charges held together by ionic bonds.
Giant Ionic Lattice Structure
A three-dimensional structure of alternating positive and negative ions.
Electrically Neutral
Having no net charge.
Covalent Bonding
The sharing of valence electrons between two atoms to form covalent bonds.
Covalent Compounds
Compounds with covalent bonds.
Allotropes
Different forms of the same element with different structural arrangements of atoms.
Metallic Bonds
The electrostatic forces of attraction between positively charged ions in a metal and the sea of delocalised electrons.
Alloy
A mixture of a metal with one or more other elements.
Element
A pure substance that cannot be broken down into two or more simpler substances by chemical methods.
Compound
A pure substance containing two or more elements that are chemically combined in a fixed ratio.
Mixture
A combination of two or more substances that are not chemically combined and can be separated by physical methods.

Chemical Reactions

Explore the principles behind how substances react, calculate quantities in reactions, and understand the energy and speed of chemical processes.

Mole Concept and Stoichiometry

Learn to calculate amounts of substances using moles, molar mass, and volume. Apply stoichiometric ratios to find limiting reagents, yields, and purity in chemical reactions.

Formulas
Percentage Mass of Elements in Compound
Percentage Mass =number of atoms of element in formula×Ar of the elementMr of the compound×100%= \dfrac{\text{number of atoms of element in formula} \times A_r \text{ of the element}}{M_r \text{ of the compound}} \times 100\%
Number of Moles
Number of Moles=number of particles6.02×1023 = \dfrac{\text{number of particles}}{6.02 \times 10^23}
Number of Moles of Gas
Number of Moles of Gas =volume of gas in dm324 dm3 = \dfrac{\text{volume of gas in dm}^3}{24 \text{ dm}^3}
Concentration (mol/dm3^3)
Concentration (mol/dm3^3) =number of moles of solutevolume of solvent in dm3 = \dfrac{\text{number of moles of solute}}{\text{volume of solvent in dm}^3}
Concentration (g/dm3^3)
Concentration (g/dm3^3) =mass of solute in gvolume of solvent in dm3 = \dfrac{\text{mass of solute in g}}{\text{volume of solvent in dm}^3}
Percentage Purity
Percentage Purity =mass of pure substance present in sampletotal mass of impure sample×100% = \dfrac{\text{mass of pure substance present in sample}}{\text{total mass of impure sample}} \times 100 \%
Percentage Yield
Percentage Yield =actual yieldtheoretical maximum yield×100% = \dfrac{\text{actual yield}}{\text{theoretical maximum yield}} \times 100 \%
Definitions
Relative Atomic Mass ArA_r
The average mass of one atom of an element relative to 112\frac{1}{12} the mass of an atom of carbon-12.
Relative Molecular Mass MrM_r
The average mass of one molecule of a molecular substance relative to 112\frac{1}{12} the mass of an atom of carbon-12.
Relative Formula Mass MrM_r
The average mass of one unit of an ionic compound relative to 112\frac{1}{12} the mass of an atom of carbon-12.
Mole
One mole of any substance contains 6.02×10236.02 \times 10^{23} particles, which can be atoms, molecules, ions, or sub-atomic particles.
Molar Mass
One mole of any substance has a mass equal to its relative atomic mass ArA_r, relative molecular mass, or relative formula mass MrM_r in grams.
Molar Volume
One mole of any gas occupies 24 dm3^3 at room temperature and pressure (r.t.p.).
Concentration
The amount of solute dissolved in a unit volume of solvent.
Molecular Formula
The exact number of atoms of each element in one molecule of the compound.
Empirical Formula
The simplest whole-number ratio of elements in a compound.
Stoichiometry
The ratio between the quantities of substances, measured in moles, involved in a chemical reaction.
Limiting Reagent
The reactant that is completely used up in a chemical reaction.
Excess Reagent
The reactant that remains unreacted after the reaction has completed.

Acid-Base Chemistry

Understand the properties of acids, bases, and alkalis. Learn how indicators work, and differentiate between strong and weak acids and alkalis through ionisation levels.

Definitions
Acids
A substance that produces hydrogen ions, H+^+, in aqueous solutions.
Strength of Acids
The extent of ionisation of an acid when dissolved in water.
Strong Acid
An acid that is completely ionised in an aqueous solution.
Weak Acid
An acid that is only partially ionised in an aqueous solution.
Bases
Any metal oxide or hydroxide. They contain either the oxide ion (O2−^{2-}) or the hydroxide ion (OH−^-).
Alkalis
Bases that are soluble in water.
Strength of Alkalis
The extent of ionisation of a base when dissolved in water.
Strong Alkali
An alkali that fully ionises when dissolved in water.
Weak Alkali
An alkali that only partially ionises when dissolved in water.
Indicator
A mixture of substances that changes colour when added to an acid or alkali.
Universal Indicator
An indicator that contains a mixture of substances which give different colours corresponding to different pH values.
Haber Process
An industrial process for manufacturing ammonia by combining nitrogen with hydrogen.
Reversible Reaction
A reaction that can go both forward and backward at the same time.

Qualitative Analysis

Identify unknown substances using characteristic tests. Learn how different cations, anions, and gases behave in chemical tests to draw accurate conclusions from reactions.

Redox Chemistry

Understand oxidation and reduction through electron transfer and changes in oxygen or hydrogen. Learn how electrolysis and redox reactions are used in real-life processes.

Definitions
Redox Reaction
A chemical reaction which involves oxygen being directly gained or lost.
Oxidation State
The charge an atom or an element would have if it existed as an ion in a compound.
Oxidation
The gain of oxygen or the loss of hydrogen.
Reduction
The loss of oxygen or the gain of hydrogen.
Oxidising Agent
A substance that causes another substance to undergo oxidation while it itself is reduced.
Reducing Agent
A substance that causes another substance to undergo reduction while it itself is oxidised.
Electrolysis
The process of passing an electric current through a compound to chemically separate its components.
Electrolytic Cell
A device that converts electrical energy into chemical energy.
Electrolyte
An electrically conductive substance in the molten or aqueous state.
Anode
The positive electrode connected to the positive terminal of the power source.
Cathode
The negative electrode connected to the negative terminal of the power source.
Inert Electrodes
Electrodes that do not take part in the electrolysis reaction.
Binary Ionic Compounds
Compounds made up of only two types of elements.
Molten Binary Ionic Compound
A salt containing only one cation and one anion in the liquid state.
Aqueous Solution
A solution formed when a solute dissolves in water.
Reactive Electrodes
Electrodes that take part in the electrolysis process.
Electroplating
The process of coating an object with a thin layer of metal.
Simple Cell
A device which converts chemical energy into electrical energy.
Voltmeter
A device that measures the potential difference of a cell.
Hydrogen Fuel Cell
A device that uses hydrogen as the fuel and oxygen from air as the oxidiser to produce water and electricity.

Patterns in the Periodic Table

Explore trends across periods and groups, predict element properties, and understand reactivity patterns, including metals and transition elements.

Definitions
Periodic Table
A list of elements arranged in order of increasing proton (atomic) numbers.
Groups
The vertical columns of elements in the periodic table.
Periods
The horizontal rows of elements in the periodic table.
Displacement Reaction
A reaction in which one element takes the place of another element in a compound.
Transition Metals
Metals found in groups 3-11 of the periodic table.
Reactivity Series
A list in which metals are arranged from the most reactive to the least reactive.
Ore
A compound of a metal mixed with large amounts of earth and rock.
Rusting
The process that produces rust in the presence of water and oxygen.
Sacrificial Protection
The protection of iron and steel against rusting by using a more reactive metal.
Galvanising
The process of coating iron or steel with a layer of zinc.

Chemical Energetics

Learn how energy changes during reactions. Understand exothermic and endothermic reactions, bond energies, and how to calculate enthalpy change.

Formulas
Concentration (mol/dm3^3)
ΔH=total energy of products−total energy of reactants\Delta H = \text{total energy of products} - \text{total energy of reactants}
The difference in energy content between the reactants and products
Definitions
Endothermic Reaction
A reaction where energy is absorbed from the surroundings.
Exothermic Reaction
A reaction where energy is released into the surroundings.
Bond Energy
The amount of energy absorbed to break one mole of a chemical bond, or the energy released when one mole of that bond is formed.
Activation Energy (EaE_a)
The minimum amount of energy that colliding reactant particles must possess to react with each other.
Enthalpy Change (ΔH\Delta H)
The difference in energy content between the reactants and products.

Rate of Reactions

Study how temperature, concentration, surface area, and catalysts affect reaction speed. Use collision theory to explain and predict how changes influence rate.

Definitions
Rate of Reaction
A measure of how fast the reactants change into products in a given time during a reaction. Rate of reaction ∝1time\propto \frac{1}{\text{time}}.
Effective Collision
A collision that results in a chemical reaction between particles.
Collision Theory
States that for a chemical reaction to occur, reacting particles must collide with energy greater than or equal to the activation energy.
Catalyst
A substance that increases the rate of a chemical reaction without being chemically changed at the end of the reaction.

Chemistry in a Sustainable World

Discover how chemistry addresses global environmental challenges, promotes clean energy, and supports a more sustainable future.

Organic Chemistry

Learn about hydrocarbons and key functional groups such as alcohols, acids, and esters. Understand how fuels are used, how combustion works, and how polymers and biofuels contribute to modern life.

Definitions
Fuels
Substances which produce a large amount of thermal energy when burnt in the presence of oxygen.
Natural Gas
A gaseous fossil fuel consisting mainly of methane.
Non-renewable Energy Sources
Sources that are limited in amount and cannot be replaced quickly enough to keep up with our rate of use.
Biofuels
Alternative, renewable energy sources derived from plants or animals.
Renewable Energy Sources
Energy sources that can be replenished in a short period of time or have no risk of depletion.
Homologous Series
A family of compounds with the same general formula and similar chemical properties due to the same functional group.
Functional Group
An atom or group of atoms that gives organic molecules their distinctive chemical properties.
Hydrocarbons
Compounds that contain only the elements carbon and hydrogen.
Alkanes
Hydrocarbons that contain only carbon-carbon single bonds and carbon-hydrogen bonds.
Alkenes
Hydrocarbons that contain carbon-carbon double bonds.
Alcohols
Organic compounds with the hydroxyl functional group.
Carboxylic Acids
Organic compounds with the carboxyl functional group.
Esters
Organic compounds formed by the reaction of alcohols with carboxylic acids.
Isomers
Compounds with the same molecular formula but different structural formulae.
Complete Combustion
Combustion that occurs with excess oxygen.
Incomplete Combustion
Combustion that occurs with an insufficient amount of oxygen.
Saturated Molecules
Molecules that contain only carbon-carbon single bonds.
Unsaturated Molecules
Molecules that contain carbon-carbon double bonds.
Polyunsaturated Fats
Hydrocarbon chains with two or more carbon-carbon double bonds in each chain.
Cracking
The process of breaking down large hydrocarbon molecules into smaller hydrocarbon molecules.
Polymers
Very large organic molecules built from many small units called monomers.

Maintaining Air Quality

Understand the causes and effects of air pollution and global warming. Explore how chemistry is used to reduce emissions, neutralise pollutants, and support environmental sustainability through processes like flue gas desulfurisation and liming.

Definitions
Non-biodegradable
Describes substances that cannot be broken down easily by decomposers such as bacteria.
Air Pollution
The introduction of unwanted and harmful chemicals into the atmosphere.
Flue Gas
Waste gas containing high amounts of sulfur dioxide released from waste incinerators and power plants that burn fuels such as coal and fuel oil.
Flue Gas Desulfurisation
A technology used to remove a significant amount of sulfur dioxide from flue gas before it is released into the atmosphere.
Liming
The process of adding calcium carbonate to soil or water bodies to neutralise excess acid from acid rain.
Carbon Cycle
A set of processes that regulate the amount of carbon dioxide in the atmosphere.
Global Warming
The increase in the average temperature of the Earth's surface due to rising levels of greenhouse gases in the atmosphere.