IGCSE Chemistry Complete Revision: Principles, Inorganic, Physical & Organic Chemistry

Comprehensive practice flashcards defining core vocabulary, definitions, equations, and experimental setups across IGCSE Chemistry topics.

Kinetic Particle Theory

A fundamental theory stating that all matter is made of tiny particles (atoms or molecules) in continuous motion, attracted by intermolecular forces, moving faster when heated, with lighter particles diffusing faster than heavier ones.

Diffusion

The spreading out and mixing of particles from a region of higher concentration to a region of lower concentration until they are evenly distributed.

Volatile Liquid

A liquid that has a relatively low boiling point and evaporates readily at room temperature.

Sublimation

The direct physical phase change of a substance from a solid to a gas without passing through an intermediate liquid state.

Evaporation vs. Boiling

Evaporation occurs at any temperature below the boiling point and exclusively at the surface of a liquid, whereas boiling happens at a specific temperature (the boiling point) and involves particles throughout the entire volume of liquid turning into gas.

Solubility

The maximum mass of solute in grams that can dissolve completely in $100\,g$ of a given solvent at a specified temperature.

Saturated Solution

A chemical solution containing the maximum possible amount of dissolved solute in a solvent at a specific temperature, such that no more solute can dissolve.

Element

A pure substance composed exclusively of atoms with the same atomic number that cannot be split into anything simpler by chemical means.

Compound

A pure substance formed of two or more different elements chemically bonded together in a fixed ratio, possessing entirely new chemical and physical properties distinct from its constituent elements.

Mixture

A combination of two or more different substances physically blended in variable proportions without chemical bonding, where each substance retains its original individual properties and can be separated by physical methods.

Physical Change vs. Chemical Change

A physical change produces no new chemical substances and is typically reversible (e.g., melting, freezing, dissolving), whereas a chemical change produces new substances through a reaction, is usually irreversible, and is accompanied by energy changes, color changes, gas evolution, or precipitate formation.

Filtration

A physical separation technique used to separate an insoluble solid from a liquid based on differences in particle size, producing a filtrate (the liquid that passes through the filter paper) and a residue (the solid left behind).

Crystallization

A separation method used to obtain a pure crystalline solid from a solution of a soluble solid by heating until the crystallization point is reached, allowing the mixture to cool slowly so solubility decreases, filtering the formed crystals, and drying them between filter papers.

Fractional Distillation

A separation method used to separate miscible liquids with different boiling points using a fractionating column packed with glass beads to provide a large surface area for repeated condensation and evaporation cycles.

Paper Chromatography

A separation and analytical technique based on differences in solubility and density, used to separate colored dyes, identify unknown components (such as amino acids or sugars using locating agents), and evaluate the purity of substances.

$R_f$ Value (Retention Factor)

The ratio of the distance travelled by a particular chemical substance to the distance travelled by the solvent front from the pencil baseline: $R_f = \frac{\text{Distance travelled by the substance}}{\text{Distance travelled by the solvent}}$.

Subatomic Particles

The three fundamental particles that comprise an atom: protons (relative charge $+1$, relative mass $1$), neutrons (relative charge $0$, relative mass $1$), and electrons (relative charge $-1$, relative mass $\frac{1}{2000}$).

Mass Number (Nucleon Number)

The total number of protons and neutrons located inside the nucleus of an atom.

Atomic Number (Proton Number)

The number of protons found inside the nucleus of an atom, which uniquely determines the element's identity and its position in the periodic table.

Isotopes

Atoms of the same element that have the identical number of protons (same atomic number) but a different number of neutrons (different mass number), exhibiting identical chemical properties because they share the same electronic configuration.

Relative Atomic Mass ($A_r$)

The weighted average mass of the naturally occurring isotopes of an element compared to $\frac{1}{12}\text{th}$ the mass of an atom of Carbon-12.

Group VIII / Group 0 (Noble Gases)

A family of unreactive, non-metal, monatomic colorless gases with a stable full outer shell of 8 valence electrons (or 2 for Helium), including Helium (used in balloons), Neon (used in advertising signs), and Argon (used in incandescent light bulbs).

Empirical Formula

A chemical formula that represents the simplest whole number ratio of the different atoms or ions present in a compound.

Molecular Formula

A chemical formula that indicates the exact number and identity of each type of atom present in one molecule of a compound ($\text{Molecular Formula} = n \times \text{Empirical Formula}$).

Valency

The combining power of an atom or radical, representing the number of electrons an atom loses, gains, or shares to achieve a stable full outer shell configuration ($\text{Valency} = 8 - \text{valence electrons}$ for non-metals in Groups 5 to 7).

Polyatomic Ions (Radicals)

A group of covalently bonded atoms that collectively carry an overall electrical charge and act as a single unit in chemical reactions (e.g., Ammonium $\text{NH}_4^+$, Hydroxide $\text{OH}^-$, Nitrate $\text{NO}_3^-$, Carbonate $\text{CO}_3^{2-}$, Sulfate $\text{SO}_4^{2-}$, and Phosphate $\text{PO}_4^{3-}$).

Spectator Ions

Ions in a chemical reaction that remain unchanged in physical state and charge on both the reactant and product sides of the total ionic equation, and are eliminated when writing the net ionic equation.

Mole

The standard SI unit for amount of substance (symbol $\text{mol}$) containing Avogadro's constant ($6.02 \times 10^{23}$) of specified particles, equivalent to the relative formula mass ($M_r$) or relative atomic mass ($A_r$) expressed in grams.

Molar Gas Volume

The volume occupied by one mole of any gas at room temperature and pressure (rtp), which is equal to $24\,dm^3$ (or $24000\,cm^3$).

Limiting Reactant

The reactant that is completely consumed first in a chemical reaction, which strictly determines and limits the maximum theoretical yield of product that can be formed.

Excess Reactant

A reactant present in a quantity greater than that required to react stoichiometrically with the limiting reactant, leaving unreacted material remaining upon completion.

Percentage Yield

The percentage efficiency of a chemical reaction, calculated as: $\text{\% Yield} = \frac{\text{Actual yield}}{\text{Theoretical yield}} \times 100$.

Redox Reaction

A chemical reaction in which reduction and oxidation processes occur simultaneously.

OIL RIG

A scientific mnemonic defining electron transfer in chemical systems: Oxidation Is Loss of electrons, and Reduction Is Gain of electrons.

Oxidizing Agent (Oxidant)

A reactant that oxidizes another chemical substance by removing electrons or donating oxygen, and in doing so undergoes reduction itself.

Reducing Agent (Reductant)

A reactant that reduces another chemical substance by supplying electrons or removing oxygen, and in doing so undergoes oxidation itself.

Oxidation Number

A value indicating the degree of oxidation of an atom in a chemical compound, where uncombined pure elements have an oxidation number of 0, the sum in a neutral compound equals 0, and the sum in a polyatomic ion equals its net ionic charge.

Alloy

A metallic mixture composed of a pure metal combined with other elements to enhance structural properties, rendering it harder and stronger because different-sized atoms distort the regular crystal lattice, preventing layers from sliding over each other.

Rusting

The specific chemical corrosion of iron and steel requiring both oxygen and liquid water, yielding a brittle reddish-brown coating of hydrated iron(III) oxide: $4\text{Fe}(s) + 3\text{O}_2(g) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{Fe}_2\text{O}_3 \cdot 2\text{H}_2\text{O}(s)$.

Galvanizing

The industrial process of coating iron or steel with a protective layer of metallic zinc to prevent rust, offering continued sacrificial protection even if the coating is scratched.

Sacrificial Protection

A method of rust prevention where blocks of a more reactive metal (e.g., zinc or magnesium) are attached to iron; the more reactive metal oxidizes preferentially, donating electrons to the iron and sparing it from corrosion.

Thermal Decomposition

The endothermic breakdown of a single chemical compound into two or more simpler chemical products solely by the application of heat.

Blast Furnace Extraction of Iron

The industrial reduction of iron from hematite ore ($\text{Fe}_2\text{O}_3$) using coke in a blast furnace, where coke burns exothermically to $\text{CO}_2$, which reacts with excess coke to yield the reducing agent carbon monoxide ($\text{CO}$), reducing the iron oxide to molten iron: $\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$.

Acid (Brønsted–Lowry)

A chemical species that acts as a proton donor ($\text{H}^+$ donor), having a $\text{pH} < 7$, turning blue litmus paper red, and reacting with bases, carbonates, and reactive metals.

Base (Brønsted–Lowry)

A chemical species that acts as a proton acceptor ($\text{H}^+$ acceptor), typically a metal oxide, metal hydroxide, or ammonia; water-soluble bases are categorized as alkalis ($\text{pH} > 7$).

Strong Acid vs. Weak Acid

A strong acid completely ionizes/dissociates in aqueous solution yielding a high concentration of $\text{H}^+$ ions ($\text{pH } 1-3$, e.g., $\text{HCl}$, $\text{HNO}_3$, $\text{H}_2\text{SO}_4$), whereas a weak acid only partially ionizes in water yielding a low concentration of $\text{H}^+$ ions ($\text{pH } 4-6$, e.g., $\text{CH}_3\text{COOH}$).

Neutralization Reaction

An exothermic chemical reaction between an acid and a base (or metal carbonate or ammonia) yielding a salt and neutral products, with the fundamental net ionic equation: $\text{H}^+(aq) + \text{OH}^-(aq) \rightarrow \text{H}_2\text{O}(l)$.

Precipitate

An insoluble solid product that separates from solution during a precipitation reaction when two soluble electrolyte solutions are combined.

Titration (Salt Preparation)

A quantitative neutralization method used specifically to prepare soluble sodium, lithium, potassium, and ammonium (SLAP) salts from an acid and an alkali, employing an indicator to detect the exact neutralization end point.

Exothermic Reaction

A chemical reaction that releases net thermal energy to the surroundings, causing the surrounding temperature to increase ($\Delta H$ is negative), where the energy released during bond making in products is greater than the energy required for bond breaking in reactants.

Endothermic Reaction

A chemical reaction that absorbs net thermal energy from the surroundings, causing the surrounding temperature to decrease ($\Delta H$ is positive), where the energy required for bond breaking in reactants is greater than the energy released during bond formation in products.

Activation Energy ($E_a$)

The minimum kinetic energy that colliding reactant particles must possess in order to undergo an effective collision and initiate a chemical reaction.

Specific Heat Capacity ($c$)

The quantity of heat energy required to raise the temperature of $1\,g$ of a specified substance by $1^\circ\text{C}$ (for water, $c = 4.2\,\text{J}\,g^{-1}\,^\circ\text{C}^{-1}$).

Heat Energy Change ($Q$)

The total quantity of heat transferred during a calorimetry experiment, calculated using the formula: $Q = m \times c \times \Delta T$, where $m$ is the mass of the liquid, $c$ is the specific heat capacity, and $\Delta T$ is the measured temperature change.

Hydrocarbon

An organic molecule composed exclusively of hydrogen and carbon atoms.

Homologous Series

A family of organic compounds sharing the same functional group, identical general formula, similar chemical reactivity, a common increment of a $-\text{CH}_2-$ unit between consecutive members, and displaying a gradual gradation in physical properties.

Functional Group

An atom or specific group of covalently bonded atoms within an organic molecule that dictates its characteristic chemical reactivity and properties.

Alkanes (Saturated Hydrocarbons)

A homologous series of saturated hydrocarbons containing exclusively single carbon-carbon bonds ($\text{C}-\text{C}$), with the general chemical formula $\text{C}_n\text{H}_{2n+2}$.

Alkenes (Unsaturated Hydrocarbons)

A homologous series of unsaturated hydrocarbons containing at least one carbon-carbon double covalent bond ($\text{C}=\text{C}$), with the general chemical formula $\text{C}_n\text{H}_{2n}$.

Structural Isomerism

The phenomenon in which chemical compounds possess the identical molecular formula but exhibit different structural arrangements of their bonded atoms.

Addition Reaction

A chemical reaction characteristic of unsaturated compounds (such as alkenes) in which a carbon-carbon double bond ($\text{C}=\text{C}$) breaks open to bond with additional atoms, producing a single saturated product.

Bromine Water Test

A diagnostic chemical test used to distinguish between alkanes and alkenes; alkenes undergo an addition reaction that rapidly decolorizes orange-brown bromine water to colorless, whereas alkanes show no reaction without ultraviolet light.

Petroleum Fraction

A distinct group of hydrocarbons collected together during fractional distillation of crude oil that share similar boiling points and molecular chain lengths, condensing at specific heights in the fractionating column.

Cracking

The thermal decomposition process by which long-chain, less economically useful alkanes are broken down into shorter-chain, more useful alkanes and alkenes (or hydrogen) at high temperatures ($600-700^\circ\text{C}$) using an alumina or silica catalyst.