A glossary of more than twenty key terms for Acids, Bases and Salts, from acid, base and alkali to molarity, standard solution, titration and qualitative analysis, each defined in the precise wording the marking scheme rewards.
Learn each term as a definition you can write from memory, because the marking scheme rewards exact wording. Each entry gives the term in English (with the Malay and Chinese equivalents) and a precise definition. Keep this list beside the revision notes and test yourself by covering the definition and recalling it.
Acids, bases and alkalis
- Acid (asid / 酸), a substance that ionises in water to produce hydrogen ions, H⁺. Its acidic properties appear only in the presence of water.
- Base (bes / 碱), a metal oxide or metal hydroxide that reacts with an acid to form a salt and water.
- Alkali (alkali / 碱液), a base that is soluble in water; it ionises in water to produce hydroxide ions, OH⁻.
- Strong acid (asid kuat / 强酸), an acid that ionises completely in water to release a high concentration of hydrogen ions.
- Weak acid (asid lemah / 弱酸), an acid that ionises only partially in water, so fewer hydrogen ions are released.
- Basicity of an acid (kebesan asid / 酸的元数), the number of hydrogen ions an acid molecule can release; hydrochloric acid is monoprotic and sulfuric acid is diprotic.
The pH scale
- pH scale (skala pH / pH值), a scale from 0 to 14 that measures how acidic or alkaline a solution is, based on the concentration of hydrogen ions.
- Neutral (neutral / 中性), a solution with pH 7, such as pure water, in which the concentrations of H⁺ and OH⁻ ions are equal.
- Indicator (penunjuk / 指示剂), a substance that shows a different colour in acidic and alkaline solutions; universal indicator shows a range of colours across the pH scale.
Concentration and molarity
- Concentration (kepekatan / 浓度), the amount of solute dissolved in a given volume of solution, expressed in g dm⁻³ or mol dm⁻³.
- Molarity (kemolaran / 摩尔浓度), the number of moles of solute dissolved in one cubic decimetre (dm³) of solution, in mol dm⁻³.
- Molar mass (jisim molar / 摩尔质量), the mass of one mole of a substance, in g mol⁻¹, used to convert between grams and moles.
- Mole (mol / 摩尔), the unit for the amount of a substance; the link between mass, molarity and volume in every calculation in this chapter.
Standard solution and dilution
- Standard solution (larutan piawai / 标准溶液), a solution whose concentration is accurately known, prepared using a volumetric flask.
- Volumetric flask (kelalang volumetrik / 容量瓶), apparatus with a single calibration mark, used to make a solution up to an exact volume.
- Dilution (pencairan / 稀释), the addition of water to a solution to lower its concentration; the number of moles of solute does not change, giving M₁V₁ = M₂V₂.
Neutralisation and titration
- Neutralisation (peneutralan / 中和), the reaction between an acid and a base or alkali to produce a salt and water only; ionically, H⁺ + OH⁻ → H₂O.
- Titration (pentitratan / 滴定), a technique to find an unknown concentration by adding one solution from a burette to a fixed volume of another until the reaction is just complete.
- Pipette (pipet / 移液管), apparatus that delivers a fixed, accurate volume of solution into the conical flask.
- Burette (buret / 滴定管), apparatus that delivers a variable, measured volume of solution during a titration.
- End point (takat akhir / 终点), the point in a titration at which the indicator just changes colour, showing the reaction is complete.
- Concordant titres (titer sepadan / 一致滴定体积), burette readings that agree closely, usually within about 0.10 cm³, which are averaged to give a reliable result.
Salts and their preparation
- Salt (garam / 盐), a compound formed when the hydrogen ion of an acid is replaced by a metal ion or an ammonium ion.
- Soluble salt (garam terlarut / 可溶盐), a salt that dissolves in water; prepared by reacting an acid with a base, metal or carbonate, or by titration for sodium, potassium and ammonium salts.
- Insoluble salt (garam tak terlarut / 不可溶盐), a salt that does not dissolve in water; prepared by precipitation.
- Precipitation (pemendakan / 沉淀), the formation of an insoluble salt when two soluble solutions are mixed; also called double decomposition.
- Crystallisation (penghabluran / 结晶), the formation of crystals from a hot, saturated solution as it cools, used to obtain a pure, dry salt.
Qualitative analysis
- Qualitative analysis (analisis kualitatif / 定性分析), the identification of the ions present in a salt through a set of standard tests.
- Cation (kation / 阳离子), a positively charged ion, such as a metal ion, identified using sodium hydroxide and ammonia solutions.
- Anion (anion / 阴离子), a negatively charged ion, such as carbonate, chloride, sulfate or nitrate, identified by its own specific test.
- Spectator ion (ion penonton / 旁观离子), an ion that is present but does not change during a reaction, and so is left out of the ionic equation.
How to use these terms
Do not just read these definitions, write them out and check the exact wording. A one-to-one teacher can point out where a definition is missing a key phrase, such as “in water” for an acid or “accurately known” for a standard solution, which is where marks are quietly lost. Once these terms are secure, the revision notes, worked examples and practice questions for this chapter will read much more easily, because every one of them is built on this vocabulary.
Want a teacher to make this click?
We teach SPM Chemistry one to one, so your child understands it and scores it.
from RM50/hr · One-hour paid trial · Same-day reply