Grade 12 Chemistry Definitions

A set of vocabulary flashcards defining key Grade 12 Chemistry terms across Quantitative Chemistry, Chemical Bonding, Energy Change and Rates of Reaction, Chemical Equilibrium, Acids and Bases, Electrochemistry, and Organic Chemistry.

Molar mass

Mass in grams of one mole of that substance

Solution

Homogeneous mixture of solute and solvent

Solute

Substance that is dissolved in the solution

Solvent

Substance in which another substance is dissolved, forming a solution

Concentration

Amount of solute per unit volume of solution

Standard solution

Solution of known concentration

Yield

A measure of the extent of a reaction, generally measured by comparing the amount of product against the amount of product that is possible

Intramolecular bond

A bond which occurs between atoms within molecules

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons

Covalent bond

A sharing of at least one pair of electrons by two non-metal atoms

Non-polar covalent (pure covalent)

An equal sharing of electrons

Polar covalent

Unequal sharing of electrons leading to a dipole forming (as a result of electronegativity difference)

Ionic bond

A transfer of electrons and subsequent electrostatic attraction

Metallic bonding

A metallic bond is between a positive kernel and a sea of delocalized electrons

Intermolecular force

A weak force of attraction between molecules, ions, or atoms of noble gases

Heat of reaction (AH)

The net change of chemical potential energy of the system

Exothermic reactions

Reactions which transform chemical potential energy into thermal energy

Endothermic reactions

Reactions which transform thermal energy into chemical potential energy

Activation energy

The minimum energy required to start a chemical reaction OR The energy required to form the activated complex

Activated complex

A high energy, unstable, temporary transition state between the reactants and products

Reaction rate

Change in concentration per unit time of either a reactant or product

Catalyst

Substance that increases the rate of the reaction but remains unchanged at the end of the reaction

Closed system

A system in which mass is conserved inside the system but energy can enter or leave the system freely

Open system

A system in which both energy and matter can be exchanged between the system and its surroundings

Le Chatelier's Principle

When an external stress (change in pressure, temperature or concentration) is applied to a system in dynamic chemical equilibrium, the equilibrium point will change in such a way as to counteract the stress

Base (Lowry-Brønsted theory)

A proton ($H^+$ ion) acceptor

Acid (Lowry-Brønsted theory)

A proton ($H^+$ ion) donor

Ionisation

The reaction of a molecular substance with water to produce ions

Dissociation

The splitting of an ionic compound into its ions

Strong acids

An acid that ionises completely in an aqueous solution

Strong bases

A base that dissociates completely in an aqueous solution

Weak acids

An acid that only ionises partially in an aqueous solution

Weak bases

A base that only dissociates/ionises partially in an aqueous solution

Amphoteric (Amphiprotic)

A substance that can act as either an acid or a base

Salt

A substance in which the hydrogen of an acid has been replaced by a cation

Hydrolysis of a salt

A reaction of an ion (from a salt) with water

Neutralization/equivalence point

The point where an acid and a base have reacted so neither is in excess

Redox

A reaction involving the transfer of electrons

Oxidation

A loss of electrons

Reduction

A gain of electrons

Oxidising agent

A substance that accepts electrons

Reducing agent

A substance that donates electrons

Anode

The electrode where oxidation takes place

Cathode

The electrode where reduction takes place

Electrolyte

A substance that can conduct electricity by forming free ions when molten or dissolved in solution

Functional group

An atom or a group of atoms that form the centre of chemical activity in the molecule

Hydrocarbon

A compound containing only carbon and hydrogen atoms

Homologous series

A series of similar compounds which have the same functional group and have the same general formula, in which each member differs from the previous one by a single $CH_2$ unit

Saturated compound

A compound in which all of the bonds between carbon atoms are single bonds

Unsaturated compound

A compound in which there is at least one double and/ triple bond between carbon atoms

Structural isomer

Compounds that have the same molecular formula but different structural formulae