Physical Sciences Grade 12 Examination Guidelines Vocabulary

Vocabulary flashcards for Physical Sciences Grade 12 examination guidelines.

Structural Formula

A structural formula of a compound shows which atoms are attached to which within the molecule. Atoms are represented by their chemical symbols and lines are used to represent ALL the bonds that hold the atoms together.

Condensed Structural Formula

This notation shows the way in which atoms are bonded together in the molecule, but DOES NOT SHOW ALL bond lines.

Hydrocarbon

Organic compounds that consist of hydrogen and carbon only.

Homologous Series

A series of organic compounds that can be described by the same general formula OR in which one member differs from the next with a CH2 group.

Saturated Compounds

Compounds in which there are no multiple bonds between C atoms in their hydrocarbon chains.

Unsaturated Compounds

Compounds with one or more multiple bonds between C atoms in their hydrocarbon chains.

Functional Group

A bond or an atom or a group of atoms that determine(s) the physical and chemical properties of a group of organic compounds

Structural Isomer

Organic molecules with the same molecular formula, but different structural formulae.

Chain Isomers

Same molecular formula, but different types of chains.

Positional Isomers

Same molecular formula, but different positions of the side chain, substituents or functional groups on the parent chain.

Functional Isomers

Same molecular formula, but different functional groups.

Boiling Point

The temperature at which the vapour pressure of a substance equals atmospheric pressure. The stronger the intermolecular forces, the higher the boiling point.

Melting Point

The temperature at which the solid and liquid phases of a substance are at equilibrium. The stronger the intermolecular forces, the higher the melting point.

Vapour Pressure

The pressure exerted by a vapour at equilibrium with its liquid in a closed system. The stronger the intermolecular forces, the lower the vapour pressure.

Cracking of Alkanes

The chemical process in which longer chain hydrocarbon molecules are broken down to shorter more useful molecules.

Hydrolysis

The reaction of a compound with water

Heat of Reaction (ΔH)

The energy absorbed or released in a chemical reaction.

Exothermic Reactions

Reactions that release energy.

Endothermic Reactions

Reactions that absorb energy.

Activation Energy

The minimum energy needed for a reaction to take place.

Activated Complex

The unstable transition state from reactants to products.

Reaction Rate

The change in concentration of reactants or products per unit time.

Catalyst

A substance that increases the rate of a chemical reaction without itself undergoing a permanent change.

Open and Closed Systems

An open system continuously interacts with its environment, while a closed system is isolated from its surroundings.

Reversible Reaction

A reaction is reversible when products can be converted back to reactants and vice versa.

Chemical Equilibrium

It is a dynamic equilibrium when the rate of the forward reaction equals the rate of the reverse reaction.

Le Chatelier's Principle

When the equilibrium in a closed system is disturbed, the system will re-instate a new equilibrium by favouring the reaction that will oppose the disturbance.

Arrhenius Theory (Acids and Bases)

Acids produce hydrogen ions (H+/H3O+/hydronium ions) in aqueous solution; Bases produce hydroxide ions (OH-) in aqueous solution.

Lowry-Brønsted Theory (Acids and Bases)

An acid is a proton (H+ ion) donor; A base is a proton (H+ ion) acceptor.

Hydrolysis (in acid-base context)

The reaction of a salt with water.

Equivalence Point (of a titration)

The point at which the acid/base has completely reacted with the base/acid.

Endpoint (of a titration)

The point where the indicator changes colour.

pH Scale

A scale of numbers from 0 to 14 used to express the acidity or alkalinity of a solution.

Kw

The equilibrium constant for the ionisation of water or the ion product of water or the ionisation constant of water, i.e. Kw = [H3O+][OH-] = 1 x 10-14 by 298 K.

Auto-ionisation of Water

The reaction of water with itself to form H3O+ ions and OH- ions.

Galvanic Cell

A cell in which chemical energy is converted to electrical energy.

Oxidation

A loss of electrons

Reduction

A gain of electrons.

Oxidising agent

A substance that is reduced/gains electrons.

Reducing Agent

A substance that is oxidised/loses electrons.

Anode

The electrode where oxidation takes place.

Cathode

The electrode where reduction takes place.

Electrolyte

A substance of which the aqueous solution contains ions OR a substance that dissolves in water to give a solution that conducts electricity.

Electrolytic cell

A cell in which electrical energy is converted into chemical energy OR the use of electrical energy to produce a chemical change.

Electrolysis

The chemical process in which electrical energy is converted to chemical energy.