O-Level Chemistry Comprehensive Vocabulary

Comprehensive vocabulary and definitions spanning the entire O-Level Chemistry curriculum based on the secondary school lecture notes.

Chemistry

A science that deals with the composition, structure and properties of matter.

Matter

Anything that has mass and occupies space.

Alchemists

The people who studied Chemistry in ancient times.

Laboratory

A special room or building that is designed and used for scientific experiments.

First Aid

The help given to a sick/injured person before getting professional medical help.

Scalds

Injuries resulting from contact with hot liquids or vapour.

Heimlich manoeuvre

A procedure involving quick upward thrusts near the top of the stomach to dislodge an object from a choking victim's airway.

Shock

A condition in which the body system is unable to take enough blood to the vital organs, such as the heart, lungs, and brain.

Flame

A zone of burning gases that produces heat and light; it is the visible glowing part of a fire.

Luminous flame

A yellow flame that produces soot and less heat, typically occurring when the oxygen supply is insufficient for complete combustion.

Non-luminous flame

A blue flame that does not produce soot and gives more heat, occurring when the oxygen supply is sufficient for complete combustion.

Hypothesis

An intelligent guess that tries to explain a scientific observation.

Dependent variable

The condition in a scientific experiment that is measured or observed to obtain results.

Atom

The smallest part of an element which can take part in a chemical reaction.

Sublimation

The change of physical state directly from solid to gas.

Brownian motion

The law stating that matter is made up of tiny particles that are in a state of continuous random motion.

Physical changes

Changes which do not alter the identity of a substance, though physical properties like size or state may vary.

Chemical changes

Changes which alter the identity of matter/substance, resulting in the formation of new substances.

Element

A pure chemical substance which cannot be split into simple substances by a simple chemical process.

Compound

A pure substance made up of more than one element in a chemical combination in a fixed ratio.

Homogenous mixture

A type of mixture that has uniform composition, appearance, and properties throughout.

Supersaturated solution

A solution that temporarily holds more solute than the saturated solution at a given temperature.

Suspension

A heterogeneous mixture of liquid and fine particles of a solid that settle at the bottom if undisturbed.

Decantation

The process of separating a heterogeneous mixture of a liquid and solid by pouring out the liquid and leaving the solid at the bottom.

Distillate

The cooled vapour obtained and collected during the process of distillation.

Combustion

A chemical reaction involving the burning of a substance in the presence of oxygen to release energy in the form of heat and light.

Fire Triangle

The three components needed to start and maintain a fire: fuel, oxygen, and heat.

Rusting

The reddish-brown coating that occurs on iron or steel in the presence of air ($O_2$) and water ($H_2O$).

Galvanization

The process of mixing or coating iron/steel with a metal that does not rust, such as zinc, to prevent corrosion.

Catalyst

A substance that speeds up the rate of a chemical reaction but remains chemically unchanged at the end of the reaction.

Hydrogenation

The process whereby hydrogen reacts with another chemical substance, such as hardening liquid oil to form margarine using a nickel catalyst.

Water Cycle

The system, also called the Hydrological Cycle, whereby water is recycled through evaporation, condensation, precipitation, and collection.

Universal Solvent

A description for water because it dissolves more substances than any other liquid.

Ignition point

The definite temperature needed to burn a specific fuel.

Energy value

The total amount of heat liberated by the complete combustion of a unit mass of fuel in oxygen, measured in $J/g$ or $kJ/kg$.

Protons

Positively charged subatomic particles located in the nucleus of an atom, denoted by $p$, with a charge of $+1.6 \times 10^{-19}\,C$.

Electronic configuration

The arrangement of electrons in the different shells or energy levels of an atom.

Atomic number ($Z$)

The number of protons found in the nucleus of a particular element's atom.

Isotopes

Atoms of the same element with the same atomic number but different atomic masses due to varying numbers of neutrons.

Relative Atomic Mass ($RAM$)

The average mass of an element relative to $\frac{1}{12}$th the mass of one carbon-12 atom.

Periodic Law

The principle stating that the properties of elements are a periodic function of their relative atomic masses (historically) or atomic numbers (modern).

Electronegativity

The ability of an atom to attract an electron towards itself.

Bonding

A method whereby atoms become more stable by donating, gaining, or sharing electrons, held together by a force of attraction.

Valency

The electron number of an atom which it donates, shares, or receives in the formation of a chemical bond.

Empirical Formula

The formula which represents the simplest ratio of the atoms or ions in a compound.

Spectator Ions

Ions in a chemical reaction that do not change their valency or participate directly in the reaction.

Mole

The amount of a substance which contains the Avogadro’s constant ($6.022 \times 10^{23}$) of particles.

Molarity ($M$)

The concentration of a solution expressed in moles per litre ($mol/dm^3$).

Standard solution

A solution of precisely known concentration used in volumetric analysis.

Electrolyte

A solution or molten substance whose ions are dissociated into free ions, allowing electric current to pass through.

Activation Energy ($E_a$)

The minimum energy possessed by reactant particles required to undergo a chemical reaction.

Le Chatelier’s Principle

The principle stating that if a system at equilibrium is subjected to change, processes occur which tend to counteract that change.

Metallurgy

The branch of science concerned with the properties, production, and purification of metals.

Ore

A mineral that contains a large proportion of a metallic compound that has economic value.

Allotropy

The existence of an element in two or more different physical forms in the same physical state, such as diamond and graphite for carbon.

Ozone Layer

A layer in the earth’s stratosphere containing high concentrations of ozone ($O_3$) which absorbs ultraviolet light from the sun.

Eutrophication

A condition where excess nutrients in water bodies cause excessive growth of aquatic plants and algae, leading to oxygen depletion.