Secondary 6 Chemistry

The unit of amount of substance; one mole contains 6.02×10²³ specified particles.

6.02×10²³ mol⁻¹, the number of particles in one mole of a substance.

The mass of one mole of a substance, numerically equal to its relative atomic or molecular mass, in g mol⁻¹.

The relative mass of an atom compared with 112 of the mass of a carbon-12 atom.

About 24 dm³ per mole of any gas at room temperature and pressure.

The number of moles of solute per dm³ of solution, in mol dm⁻³.

Calculating the amounts of reactants and products from the coefficient ratios of a balanced equation.

The simplest whole-number ratio of atoms of each element in a compound.

A chemical equation with equal numbers of each type of atom on both sides; its coefficients give the mole ratios.

The number in front of a formula in an equation, giving the mole ratio of that species.

A reaction involving oxidation and reduction together; in essence, electron transfer.

The loss of electrons; the oxidation number rises.

The gain of electrons; the oxidation number falls.

A species that oxidises another and is itself reduced, e.g. oxygen, potassium permanganate.

A species that reduces another and is itself oxidised, e.g. carbon, carbon monoxide, hydrogen.

A number showing the charged state of an atom in a species; its rise or fall identifies oxidation and reduction.

An equation showing only the oxidation or the reduction half, balanced with electrons.

An equation showing only the ions and molecules actually taking part in the reaction.

The movement of electrons from one species to another — the essence of redox.

A device converting the chemical energy of a spontaneous redox reaction into electrical energy.

Using electrical energy to drive non-spontaneous redox reactions, converting electrical energy into chemical energy.

A conductor in contact with an electrolyte or solution, at which oxidation or reduction occurs.

In an electrolytic cell, the electrode joined to the negative terminal, where reduction occurs.

In an electrolytic cell, the electrode joined to the positive terminal, where oxidation occurs.

A substance that conducts electricity when molten or dissolved in water, by movement of ions.

A bridge joining two half-cells, allowing ions to migrate so neutrality is kept and the internal circuit is completed.

An electrode with its electrolyte, carrying out just the oxidation or the reduction half of the reaction.

The order of metals (and their ions) by reactivity or tendency to lose or gain electrons, used to compare electrode reactions.

Using electrolysis to coat an object with a layer of metal; the object is made the cathode.

The amount of reactant consumed or product formed per unit time, describing how fast a reaction goes.

The theory that particles must collide with sufficient energy to react; it explains the factors affecting rate.

A graph of reaction progress against time; its gradient is the rate, which decreases as reactants run out.

A substance that speeds up a reaction by providing a lower-energy route, itself unchanged in mass and chemical nature.

The area of a solid reactant exposed to others; grinding the solid enlarges it and speeds up the reaction.

A reaction that proceeds in both directions, shown with the double arrow ⇌.

The state in a closed system where forward and reverse rates are equal and all concentrations stay constant.

When conditions such as concentration or temperature change, the equilibrium shifts in the direction that lessens the change.

The relative amounts of reactants and products at equilibrium; a change of conditions shifts it.

The constant Kc relating the equilibrium concentrations at a given temperature; only a temperature change alters it.

The atom group that decides the chemical properties of a family of carbon compounds, e.g. —OH, —COOH.

A series of compounds with similar structures, one general formula, and successive members differing by a fixed unit such as CH₂.

A hydrocarbon containing a carbon-carbon double or triple bond, such as an alkene; it decolourises bromine water.

A reaction in which an atom or group replaces another in a molecule, e.g. an alkane with a halogen under sunlight.

A reaction in which the unsaturated bond opens and atoms or groups add directly, e.g. an alkene with bromine.

An organic compound carrying the hydroxyl group —OH, e.g. ethanol; a primary alcohol oxidises to an aldehyde and then a carboxylic acid.

An organic acid carrying the carboxyl group —COOH, e.g. ethanoic acid, the main component of vinegar.

The product of condensing an alcohol with a carboxylic acid, usually fruity in smell, e.g. ethyl ethanoate.

The reversible reaction of an alcohol with a carboxylic acid to give an ester and water, catalysed by concentrated sulfuric acid.

The joining of unsaturated monomers by opening their double bonds into a macromolecule, e.g. ethene into polythene.

The paper covering the compulsory part of the syllabus, weighing 60% with 2 hours 30 minutes.

The paper covering the elective part, weighing 20% with 1 hour; candidates answer two of the three elective topics.

Assessment carried out at school and marked by the subject teacher, weighing 20%, including practical and investigative work.

Reporting grades by comparing performance with pre-set standards (Levels 1 to 5, with 5** the highest).

A long question with data and sub-parts, applying knowledge to various contexts — the heaviest-weighted type in Paper 1.

The marks allotted to parts of a question; time and depth of answer should be proportional to the marks.

Symbols showing states of matter — (s), (l), (g), (aq) — added to equations when required.

Writing the marking-keyword terms (e.g. collision frequency, effective collision, oxidation number falls) in explanations instead of bare conclusions.

Past examination papers — the best practice material for item styles, depth and time management.

A notebook of questions you got wrong and why; reviewing it before the exam prevents repeated mistakes.