All IEB SAGS Chemistry Definitions
Strong Base
A base that dissociates almost completely in an aqueous solution.
Weak Base
A base that only dissociates partially in an aqueous solution.
Hydrocarbon
A compound containing only carbon and hydrogen atoms.
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/or triple bond between carbon atoms.
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.
Electronegativity
A measure of the tendency of an atom to attract a bonding pair of electrons.
Hydrolysis of a Salt
A reaction with water where water itself is decomposed.
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 the previous one by a single CH₂ unit.
Covalent Bond
A sharing of a least one pair of electrons by two atoms.
Standard Solution
A solution of known concentration.
Salt
A substance in which the hydrogen of an acid has been replaced by a cation.
Oxidising Agent
A substance that accepts electrons.
Reducing Agent
A substance that donates electrons.
Catalyst
A substance that increases the rate of the reaction but remains unchanged at the end of the reaction.
Activated Complex
A temporary transition state between the reactants and the products.
Ionic Bond
A transfer of electrons and subsequent electrostatic attraction.
Intermolecular Force
A weak force of attraction between molecules or between atoms of noble gases.
Acids and Bases (Lowry-Bronsted Model)
An acid is defined as a proton donor. A base is defined as a proton acceptor.
Strong Acid
An acid that ionises almost completely in an aqueous solution.
Weak Acid
An acid that only ionises partially in an aqueous solution.
Functional Group
An atom or a group of atoms that form the centre of chemical activity in the molecule.
Non-Polar (Pure) Covalent Bond
An equal sharing of electrons.
Polar Covalent
An unequal sharing of electrons leading to a dipole forming (as a result of electronegativty difference).
Intramolecular Bond
Bond occurring between atoms within molecules.
Metallic Bonding
Bonds between a positive kernel and a sea of delocalised electrons.
Isomers
Compounds having the same molecular formula but different structural formulae.
Exothermic Reactions [∆H < 0]
Reactions which transfer potential energy into thermal energy. Bond formation.
Endothermic Reactions [∆H > 0]
Reactions which transfer thermal energy into potential energy. Bond breaking.
Reaction Rate
The change in concentration per unit time of either a reactant or product.
Anode
The electrode where oxidation takes place.
Cathode
The electrode where reduction takes place.
Reduction
The gain of electrons.
Oxidation
The loss of electrons.
Molar Mass
The mass in grams of one mole of that substance.
Activation Energy
The minimum energy required to start a chemical reaction.
Heat of Reaction [∆H]
The net change of chemical potential energy of the system.
Concentration
The number of moles of solute per volume of solution.
Neutralisation
The point where an acid and base have reacted so neither is in excess. Also defined as the equivalence point.
Solvent
The substance in which another substance is dissolved, forming a solution.
Solute
The substance that is dissolved in the solution.
Le Chatelier's Principles
When an external stress (change in pressure, temperature or concentration) is applied to a system in chemical equilibrium, the equilibrium point will change in such a way as to counteract the stress.
