Chemistry

Vocabulary flashcards covering Grade 12 Organic Chemistry, Rate and Extent of Reaction, Chemical Equilibrium, and Acids and Bases guidelines.

Organic molecules

Molecules containing carbon atoms.

Molecular formula

A chemical formula that indicates the type of atoms and the correct number of each in a molecule.

Structural formula

A formula of a compound that shows which atoms are attached to which within the molecule, using chemical symbols for atoms and lines to represent ALL the bonds that hold the atoms together.

Condensed structural formula

Notation showing 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 by a $CH_2$ 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

Organic molecules with the same molecular formula, but different types of chains.

Positional isomers

Organic molecules with same molecular formula, but different positions of the side chain, substituents or functional groups on the parent chain.

Functional isomers

Organic molecules with the same molecular formula, but different functional groups.

Vapour pressure

The pressure exerted by a vapour at equilibrium with its liquid in a closed system.

Boiling point

The temperature at which the vapour pressure of a substance equals the (external) atmospheric pressure.

Melting point

The temperature at which the solid and liquid phases of a substance are at equilibrium.

Cracking of alkanes

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

Heat of reaction ($\Delta H$)

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 OR change in the amount/mass/number of moles/volume of reactants or products per unit time.

Catalyst

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

Collision theory

A model that explains reaction rate as the result of particles colliding with a certain minimum energy to form products.

Open system

A system that continuously interacts with its environment.

Closed system

A system that is isolated from its surroundings.

Reversible reaction

A reaction where products can be converted back to reactants.

Chemical equilibrium

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 acid

Acids produce hydrogen ions ($H^+$) or hydronium ions ($H_3O^+$) in an aqueous solution.

Arrhenius base

Bases produce hydroxide ions ($OH^-$) in an aqueous solution.

Lowry-Brønsted acid

An acid is a proton ($H^+$ ion) donor.

Lowry-Brønsted base

A base is a proton ($H^+$ ion) acceptor.

Strong acids

Ionise completely in water to form a high concentration of $H_3O^+$ ions. Examples are hydrochloric acid, sulphuric acid and nitric acid.

Weak acids

Ionise incompletely in water to form a low concentration of $H_3O^+$ ions. Examples are ethanoic acid and oxalic acid.

Strong bases

Dissociate completely in water to form a high concentration of $OH^-$ ions. Examples are sodium hydroxide and potassium hydroxide.

Weak bases

Dissociate incompletely in water to form a low concentration of $OH^-$ ions. Examples are ammonia, calcium carbonate, potassium carbonate and sodium hydrogen carbonate.

Concentrated acids/bases

Contain a large amount (number of moles) of acid/base in proportion to the volume of water.

Dilute acids/bases

Contain a small amount (number of moles) of acid/base in proportion to the volume of water.

Hydrolysis

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.

Galvanic cell

A cell in which chemical energy is converted into electrical energy

Electrolytic cell

A cell in which electrical energy is converted into chemical 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/ gains 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.

Electrolysis

The chemical process in which electrical energy is converted to chemical energy OR the use of electrical energy to produce a chemical change.