Definitions Year 1 Flashcards
Acid
A species that release H+ ions in aqueous solutions
Activation energy
The minimum energy required to start a reaction by the breaking of bonds
Actual yield
The amount of product obtained by a reaction
Addition polymerisation
Formation of a very long molecule chain by repeated addition reactions of many unsaturated molecules
Addition reaction
a reaction where two reactants join together to form one product
Adsorption
the process that occurs when a gas or liquid or solute is held to the surface of a solid
Alicyclic
Containing carbon atoms that are joined together in a ring that is not aromatic
Aliphatic
Containing carbon atoms joined together in unbranched or branched chains
Alkali
A type of base that dissolves in water to release hydroxide ions
Alkanes
Hydrocarbon homologous series that are made up of saturated carbon chains containing only hydrogen and carbon
Alkenes
Hydrocarbon homologous series that contains at lest one carbon-to-carbon double bond
Alkyl group
a side chain formed by removing a hydrogen atom removed form an alkane parent chain
Alkynes
Hydrocarbon homologous series with at least one carbon-to-carbon triple bond
Amount of substance
the quantity whose unit is the mole
Anhydrous
Contains no water molecules
Anion
A negatively charged ion with more electrons than protons
Aromatic
Contains one or more benzene rings
Atomic number
The number of protons in the nucleus of an atom
Atomic orbital
A region around the nucleus that can hold up to two electrons with opposite spins
Average bond enthalpy
the average enthalpy change that takes place by breaking by homolytic fission one mole of a given type of bond in the molecules of a gaseous species
Avogadro constant
the number of atoms per mole of carbon-12
Avogadro’s hypothesis
Equal volumes of gases at the same temperature and pressure contain the same number of molecules
Base
A compound that neutralises an acid to form a salt
Binary compound
A compound containing only two elements
Bond angle
The angle between two bonds at an atom
Bonded pair
A pair of electrons shared between two atoms to form a covalent bond
Carbocation
An ion that contains a positively charged carbon atom
Catalyst
A substance that increase the rate of reaction without being used up in the process. A catalyst provides an alternative route for the reaction with a lower activation energy
Cation
A positively charge ion with fewer electrons that protons
Chain reaction
A reaction in which the propagation steps release new radicals that continue the reaction
Cis-trans isomerism
A special type of E/Z isomerism in which there are two non-hydrogen groups and two hydrogen around the C=C double bond
Closed system
A system isolated from its surroundings
Collision theory
Two reacting particles must collide for a reaction to occur and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction
Coordinate bond
A shared pair of electrons in which the bonded pair have been provided by one of the bonded atoms only, also called a dative covalent bond
Covalent bonding
The strong electrostatic attraction between a shared pair of electrons and eh nuclei of the bonded atoms
Dehydration
An elimination reaction in which the water molecules are removed from a saturated molecule to make an unsaturated molecule
Delocalised electrons
Electrons that are shared between more than two atoms
Desorption
release of an adsorbed substance from a surface
Dipole
A separation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule has a small positive charge and the other has a small negative charge
Dipole-dipole force
an attractive force between permanent dipoles in neighbouring polar molecules
Displacement reaction
a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of its ions
Display formula
A formula that displays the relative positioning of all the atoms in a molecule and the bonds between them
Disproportionation
a redox reaction in which the same element is both oxidised and reduced
Dynamic equilibrium
the equilibrium that exists in a closed system when the rate of the forward reaction is equal the the rate of the reverse reaction and concentration do not change
E/Z isomerism
a type of stereoisomerism in which different groups attached to each carbon of a C=C double bond may be arranged differently because of the restricted rotation of the C=C bond
Electron configuration
A short hand method for showing how electrons occupy sub-shells in an atom
Electrophile
A atom or group of atoms attracted to an electron rich centre where is accepts a pair of electrons
Electronegativity
a measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
Endothermic reaction
a reaction in which the enthalpy of the products is greater than the reactants resulting in heat being taken in from the surroundings
Enthalpy
the Heat content that is stored in a chemical system.
Enthalpy change
difference in enthalpy between reactants and products of a reaction
Enthalpy cycle
a diagram showing alternative routs between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess’s law
Enthalpy profile diagram
a diagram for a reaction to compare the enthalpy of the reactants to the enthalpy of the products
Equilibrium constant
A measure of the position of equilibrium; the magnitude of the equilibrium constant indicates whether there are more reactants or products in an equilibrium system
Exothermic reaction
A reaction in which the enthalpy of the reactants is greater than the enthalpy of the products resulting in heat loss to the suroundings
Fingerprint region
an area of an infrared spectrum below 1500 cm-1 that gives a characteristic pattern for different compounds
First ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
Fragment ions
Ions formed from the break down of the molecular ion in a mass spectrometer
General formula
the simplest algebraic formula of a member of a homologous series
Giant covalent lattice
a three dimensional structure of atoms bonded together by strong covalent bonds
Giant ionic lattice
a three dimensional structure of oppositely charged ions bonded together by strong ionic bonds
Giant metallic lattice
a three dimensional structure of positive ions and delocalised electrons bonded together by strong metallic bonds
Hess’ law
if a reaction can take place by more than one route and the initial and final conditions are the same the total enthalpy change is th same for each route
Heterogenous catalysis
a reaction in which the catalyst has a different physical state from the reactants; frequently the reactants are gases and the catalyst is solid
Heterolytic fission
The breaking of a covalent bond forming a cation (positive ion) and an anion (negative ion)
Homogenous catalysis
a reaction in which the catalyst and reactants are the same physics state, which is most frequently gaseous or aqueous
Homologous series
A series of organic compounds with the same functional group but each success member is one carbon longer.
Homolytic fissions
the breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radical
Hydrated
a crystalline compound containing water molecules
Hydrogen bond
a strong dipole-dipole interaction between an electron deficient hydrogen and on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule
Hydrolysis
a reaction with water that breaks a chemical compound into two compounds, the H and OH in a water molecule becomes incorporated into teh two compounds.
Induced dipole-dipole interaction
attractive forces between induced dipoles in different molecules also called London forces
Initiation
the first stage of a radical reaction in which radicals start when a covalent bond is Brocken by homolytic fission of a covalent bond bond
Intermolecular forces
An attractive force between molecules. Intermolecular forces can be London forces, permanent dipole-dipole interactions or hydrogen bonds
Ionic bonding
the electrostatic attraction between positive and negative ions
Le chatelier’s principle
when a system in dynamic equilibrium is subjected to an external change the system readjusts itself to minimise the change and to restore equilibrium
limiting reagent
the reactant that is not in excess which will be used us first and stop the reaction
Mass number
the sum of the number of protons and neutrons in the nucleus
Metallic bonding
the electrostatic attraction between positive metal ions and delocalised electrons
Molar gas volume
the volume per mole of gas molecules at a stated temperature and pressure
Mole
the amount of any substance containing as many elementary as there are carbon-12 atoms in exactly 12g of the carbon-12 isotope
Molecular ion
the positive ion formed in mass spectrometry when a molecule loses and electron
Monomer
a small molecule that combines with many other monomers to form a polymer
Neutralisation
the reaction between an acid and a base to produce a salt
Non-polar
with non charge separation across a bond or in a molecule
Nucleophile
an atom or group of atoms that is attracted to an electron deficient carbon atom where is donated a pair of electrons to form a new covalent bond
Oxidation
loss of electrons or increase of oxidation number
Oxidation number
a measure of the number of electrons that an atom uses to bond with atoms of a different element
Oxidation state
the oxidation number
Oxidising agent
a reagent that oxidises another species
Pi bond
Q bond formed by the sideways overlap of two p-orbitals containing two electrons and with the electron density above and below the line joining the nuclei of the bonded atoms
Partial dissociation
the splitting of some of a species in a solution into aqueous ions
Pauling electronegativity value
a value assigned as a measure of the relative attraction of a bonded atom for the pair of electrons in the covalent bond
Periodicity
a repeating trend in properties of the elements across each period of teh periodic table
Permanent dipole
A small charge difference that does not change across a bond with positive and negative partial charges on the bonded atoms: the result of bonded atoms having different electronegativities
Permanent dipole-dipole interactions
Attractive forces between the permanent dipoles in different molecules
Polar molecule
A molecules with an overall dipole having taken into account and dipoles across bonds and the shape of the molecule
Polar covalent bond
a bond with a permanent dipole having positive and negative partial charges on the bonded atoms
Polyatomic ion
an ion containing more that one atom
Polymer
a large molecule formed from many thousands of repeat units of smaller molecules known as monomers
Position of equilibrium
the relative quantities of reactants and products indicating the extent of a reversible reaction at equilibrium
Principal quantum number, n
a number representing the relative overall energy of each orbital which increases with distance from the nucleus. The sets of orbitals with the same n-value are referred to as electron shells or energy levels
Propagation
the steps that continue a free radical reaction in which a radical reacts with a reactant molecule to form a new molecule and another radical causing a chain reaction
Radical
a species with an unpaired electron
Rate of reaction
the change in concentration of a reactant or product in a given time
Reducing agent
a reagent threat reduces (adds electrons to) another species
Reduction
gain of electrons or decrease in oxidation number
Reflux
the continual boiling and condensing of a reaction mixture back to the original container to ensure that the reaction takes place without the contents of the container boiling dry
Relative atomic mass
the weighed mean mass of an atom of an element compared with a 12th of a carbon-12 atom
Relative formula mass
the weighed mean mass of a formula unit of a compound compared with a 12th of the mass of a carbon-12 atom
Relative isotopic mass
The mass of an isotope compared with a 12th of a carbon-12 atom
Relative molecular mass
the weighted mean mass of a molecule of a compound compared with a 12th of a carbon-12 atom
Sigma bond
a bond formed by the overlap of one orbital from each bond of atom consisting of two electrons and with the electrons density centred around a line directly between the nuclei of the two atoms
Salt
the product of a reaction in which the H+ ions form the acid are replaced by the metal or ammonia ions
Saturated
Containing single bonds only
Saturated hydrocarbon
a hydrocarbon with single bonds only
Second ionisation energy
the energy to remove on electron from every ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
Shell
A group of atomic orbital with the same principal quantum number. Also known as a main energy level
Shielding effect
the repulsion between electrons in the inner shells. Shielding reduces the net attractive force between the positive nucleus and the outer electrons
Simple molecular lattice
a three dimensional structure of molecules bonded together by weak intermolecular bonds
Specific heat capacity
the energy required to raise the temperature of 1g of a substance by 1K
Standard enthalpy change of combustion
the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard condition with all reactants in their standard states
Standard enthalpy change of formation
the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions with all reactants in their standard states
Standard enthalpy change of neutralisation
the enthalpy change that accompanies the reaction of an acid by a base to from one mole of water under standard conditions with all reactants in their standard states
Standard enthalpy change of hydration
the enthalpy change that accompanies one mole of gaseous ions dissolving in water to become one mole of aqueous ions
Standard enthalpy change of solution
the enthalpy change that accompanies one mole of an ionic compound dissolving in water to become aqueous ions
Standard solution
a solution of known concentration
Standard state
the physical state of a compound under standard conditions of 100Kpa and 298K
Stereoisomers
compounds with the same structural formula but different arrangement of atoms in space
Strong acid
an acid that dissociates completely in a solution
Structural formula
a formula showing the minimal detail for the arrangement of atoms in a molecule
Sub-shell
a group of orbitals of the same type within a shell
Structural isomers
compounds with the same molecular formula but different structural formula
Termination
the step at the end of a radical substitution when two radicals combine to be one molecule
Theoretical yield
the yield resulting from complete conversion of reactants to products
Unsaturated
containing a multiple carbon-to-carbon bond
Water of crystallisation
water molecules that are bonded into a crystalline structure of a compound
Weak acid
an acid that dissociates only partially in a solution
