Definitions Flashcards
(155 cards)
1
Q
Acid
A
A species that is a proton donor
1
Q
Activation Energy
A
The minimum energy required to start a reaction by the breaking of bonds
1
Q
Addition Polymer
A
A very long molecular chain formed by repeated addition reactions of many unsaturated alkene molecules (monomers)
1
Q
Addition Polymerisation
A
The process in which unsaturated alkene molecules (monomers) add onto a growing polymer chain one at a time to form a very long saturated molecular chain (the addition polymer).
1
Q
Addition Reaction
A
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule.
1
Q
Adsorption
A
The process that occurs when a gas, liquid or solute is held to the surface of a solid or, more rarely, a liquid.
1
Q
1st Ionisation Energy
A
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions with a single positive (1+) charge
1
Q
2nd Ionisation Energy
A
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions with a doublepositive (2+) charge
2
Q
Alicyclic hydrocarbon
A
A hydrocarbon with carbon atoms joined together in a ring structure
3
Q
Aliphatic Hydrocarbon
A
A hydrocarbon with carbon atoms joined together in a straight or branched chains
4
Q
Alkali
A
A type of base that dissoves in water forming hydroxide ions OH- (aq) ions
5
Q
Alkanes
A
The homologous series with the general formula CnH2n+2
7
Q
Alkyl group
A
An alkane with a hydrogen atom removed eg. CH3, C2H5. Alkyl groups are often shown as ‘R’
8
Q
Amount of Substance
A
Quantity whose unit is the mole. Chemists use the “amount of substance” as a means of counting atoms
9
Q
Anhydrous
A
A substance that contains no water molecules
10
Q
Anion
A
Negatively charged ion
11
Q
Atom Economy
A
12
Q
Atomic Orbital
A
A region of space in which up to two electrons can be found with opposite spins
12
Q
Atomic (proton) number
A
The number of protons in the nucleus of the atom. The same as the number of electrons surrounding a neutrally charged atom of the element.
12
Q
Average bond enthalpy
A
The average enthalpy change that takes place when breaking by homolytic fission 1 mole of a given type of bond in the molecules of a gaseous species
13
Q
Avogadro Constant NA
A
The number of atoms per mole of the carbon-12 isotope (6.02 x10^23)
13
Q
Base
A
A species that is proton acceptor
13
Q
Biodegradable material
A
A substance that is broken down naturally in the environment by living organisms
14
Q
Bolzmann Distribution
A
The distribution of energies of molecules at a particular temperature, usually shown as a graph.
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Bond enthalpy
The enthalpy change that takes place when breaking by homolytic fission 1 mole of a given bond in the molecule of a gaseous species
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Carbanion
An organic ion in which a carbon atom has a negative charge
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Carbocation
An organic ion in which a carbon atom has a positive charge (Br2 mechanism)
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Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process.
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Cation
A positively charged ion
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Cis-trans isomerism
A special type of E/Z isomerism in which there is a non-hydrogen group and a hydrogen atom on each C of a C=C double bond. Cis --\> H atoms are on the same side (like the Z) Trans --\> H atoms are on different sides (like the E)
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Compound
A substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula
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Concentration
The amount of solute, in mole, per 1 dm^3 (1000cm^3) of solution
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Covalent Bond
A bond formed by a shared pair of electrons
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Cracking
The breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes.
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Curly Arrow
A symbol used in reaction mechanisms to show the movement of a pair of electrons in the breaking or formation of a covalent bond
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Dative Covalent Bond / Co-ordinate bond
A shared pair of electrons which has been provided by one of the bonding atoms only.
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Dehydration
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule
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Delocalised electrons
Electrons that are shared between more than two atoms esp. found in metallic bonds
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Displacement reactions
A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter's ions
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Displayed formula
A formula showing the relative positioning of all the atoms in a molecule and the bonds between them
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Disproportionation
A special type of redox in which the same species is simultaneously oxidised and reduced at the same time.
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Dynamic equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the backwards reaction
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E/Z isomerism
A type of stereoisomerism in which different groups attached to each carbon of the C=C double bond may be arranged differently in space because of restricted rotation of the C=C double bond.
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Electron configuration
The arrangement of electrons in an atom
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Electron shielding
The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons
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Electronegativity
The measure of the attraction of a bonded atoms for the pair of electrons in a covalent bond
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Electrophile
An atom (or group of atoms) that is attracted to an electron-rich centre where it accepts a pair of electrons to form a new covalent bond
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Electrophilic addition
A type of addition reaction in which an electrophile is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond
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Elimination reaction
The removal of a molecule from a saturated molecule to make an unsaturated molecule
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Empirical formula
The simplest whole number ratio of atoms of each element present in a compound
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Endothermic Enthalpy Profile Diagram
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Endothermic reaction
A reaction in which the enthalpy of products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surrounding (ΔH = +ve)
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Enthalpy cycle
A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess' Law
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Enthalpy Formula
-q/mol
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Enthalpy profile diagram
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
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Enthalpy, H
The heat content that is stored in a chemical system
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Esterification
The reaction of an alcohol with a carboxylic acid to produce an ester and water
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Ethene and Bromine Mechanism
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Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in a heat loss to the surroundings (ΔH = -ve)
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Exothermic Enthalpy Profile Diagram
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Fractional Distillation
The separation of the components in a liquid mixture into fractions which differ in boiling point (and hence chemical composition) by means of distillation (evaporation and condensation) by use of a fractionating column
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Fragmentation
The process in mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion
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Functional group
The part of the organic molecule responsible for its chemical reactions
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General formula
The simplest algebraic formula for a member of a homologous series. Eg. CnH2n+2
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Giant covalent lattice
A 3D structure of oppositely charged ions bonded together by strong covalent bonds
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Giant ionic lattice
A 3D structure of oppositely charged ions bonded together by strong ionic bonds (electrostatic forces of attraction)
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Giant metallic lattice
A 3D structure of positive ions and delocalised electrons held together by metallic bonds with strong electrostatic forces of attraction
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Greenhouse Effect
The process by which the absorption and subsequent emission of infrared radiation by atmospheric gases warms the lower atmosphere and the planet's surface
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Group
A vertical column in the Periodic Table. Elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons
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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 the same for each route
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Heterogeneous catalysis
A reaction in which the catalyst has a different physical state from the reactants; frequently, reactants are gases which the catalyst is a solid
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Heterolytic fission
The breaking of a covalent bond with both of the bonded electrons going to one of the atoms forming a cation (+ ion) and an anion (- ion)
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Homogenous catalysis
A reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state
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Homologous series
A series of organic compound with the same functional group, but with each sucessive member differing by CH2
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Homolytic fission
The breaking of a covalent bond with one of the bonded electrons going to each atom, forming two radicals.
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Hydrated
Crystalline and containing water molecules
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Hydrocarbon
A compound of hydrogen and carbon only
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Hydrogen bond
A strong dipole-dipole attraction between an electron deficient hydrogen atom (Hδ+) and a lone pair of electrons on the highly electronegative atom on a different molecule (:Oδ-)
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Hydrolysis
A reaction with water or aqueous hydroxide ions that breaks a chemical compound into two chemical compounds
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Initiation
The first step in a radical substitution in which the radicals are generated by ultraviolet radiation
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Intermolecular forces
An attractive force between neighbouring molecules. They can be van der Waals forces (induced dipole-dipole forces), permanent dipole-dipole forces or hydrogen bonds
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Ion
A positively or negatively charged atom or (covalently bonded) group of atoms (molecular ion)
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Ionic bonding
The electrostatic attraction between oppositely charged ions
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Isotopes
Atoms of the same element with different numbers of neutrons and hence different masses
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le Chatlier's principle
When a system in dynamic equilibrium is subjected to change, the position of the equilibrium will shift to minimise the change
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Limiting Reagent
The substance in a chemical reaction that runs out first
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Lone pair
An outer shell pair of electrons not involved in bonding
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Mass (Nucleon) Number
The number of particles (protons and neutrons) in the nucleus
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Mechanism
A sequence of steps showing the path taken by electrons in a reaction
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Metallic bond
The electrostatic attraction between positive metal ions and delocalised electrons
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Molar Mass M
The mass per mole of a substance. The units of molar mass are g/mol
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Molar Volume
The volume per mole of gas. The units are dm^3/mol. At STP it is roughly 24dm^3/mol
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Mole
The amount of substance containing as many particles as there are atoms in 12g of the carbon-12 isotope
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Molecular Formula
The number of atoms of each element in a molecule
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Molecular Ion M+
The positive ion formed in mass spectronomy when a molecule loses an electron
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Molecule
A small group of atoms held together by covalent bonds
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Monomer
A small molecule that combines with many other monomers to form a polymer.
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Nomenclature
A method for naming compunds
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Nucleophile
An atom (or group of atoms) that is attracted to an electron-deficient centre or atoms where it donates a pair of electrons to forma new covalent bond
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Nucleophilic Substitiution
A type of substitution reaction in which a nucleophile is attracted to an electron-deficient centre or atom where it donates a pair of electrons to form a new covalent bond
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Oxidation
Loss of electrons or an increase in oxidation number
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Oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of rules
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Oxidation Number Rules
100
Oxidising agent
A reagent that oxidises (takes electrons from) another species
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Period
A horizontal row of elements in the Periodic table. Elements show trends across a period
102
Percentage Yield Formula
104
Periodicity
A regular periodic variation of properties of elements with atomic number and position in the periodic table
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Permanent Dipole
A small charge difference across a bond resulting from a difference in electronegativities of bonded atoms
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Permanent Dipole-Dipole Force
An attractive force between permanent dipoles in neighbouring molecules
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Pi-bond (π-bond)
The reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals
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Polar covalent bond
A bond with a permanent dipole
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Polar molecule
A molecule with an overall dipole, taking into account any dipoles across bonds. Generally non-symmetrical so dipoles do not cancel out.
111
Polymer
A long molecular chain built up from monomer units
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Precipitation Reaction
The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together
112
Principle Quantum number
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
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Propagation
Second stage in radical solution. Two repeated steps in radical solution that build up the products in a chain reaction. # (means a radical dot) Eg. XH3 react with #Cl, forming #XH2 and HCl then reacting #XH2 with Cl2 to form XH2Cl and #Cl
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Radical
A species with an unpaired electron
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Rate of reaction
The change in concentration of a reactant or product in a given time
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Redox reaction
A reaction in which both reduction and oxidation take place
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Reducing Agent
A reagent that reduces (adds electrons to) another species
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Reduction
Gain of electrons or a decrease in oxidation number
120
Reflux
The continuous boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry
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Relative Atomic Mass Ar
The weighted mean mass of an atom of an element compared to one twelfth of the mass of an atom of the carbon-12 isotope
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Relative Formula Mass
The weighted mean mass of a formula unit, compared to one twelfth of the mass of an atom of the carbon-12 isotope
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Relative Isotopic Mass
The mass of an atom of an isotope compared to one twelfth of the mass of an atom of the carbon-12 isotope
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Relative Molecular Mass Mr
The weighted mean mass of a molecule compared to one twelfth of the mass of an atom of the carbon-12 isotope
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Repeat Unit
A specific arrangement of atoms that occurs in the structure over and over again. Repeat units are included in brackets, outside of which the symbol is n
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Salt
A chemical compound formed by an acid when a H+ ion from the acid has been replaced by a metal ion or another positive ion, such as the ammonium ion NH4+
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Saturated Hydrocarbon
A hydrocarbon with single bonds only
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Shell
A group of atomic orbitals with the same principle quantum number, n. Also known as the main energy level
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Simple molecular lattice
A 3D structure of molecules bonded by weak intermolecular forces
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Skeletal Formula
A simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups.
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Specific Heat Capacity, c
The energy required to raise the temperature of 1g of substance by 1°C. q=mcΔT
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Spectator Ions
Ions that are present but take no part in a chemical reaction
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Standard Conditions
A pressure of 100kPa (1 atmosphere), a stated temperature usually 298K (25°C) and a concentration of 1mol/dm^3 (if aqueous solution)
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Standard Enthalpy Change of Combustion (∆Hcө)
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, all reactions and products being in their standard states
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Standard Enthalpy Change of Formation Standard Enthalpy Change of Combustion (∆Hfө)
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
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Standard Enthalpy Change of Reaction Standard Enthalpy Change of Combustion (∆Hrө)
The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactions and products being in their standard states
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Standard Solution
A solution of a known concentration. Normally used in titrations to determine unknown information about another substance
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Standard State
The physical state of a substance under the standard condisitons of 100kPa and 298K (25°C)
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Stereoisomer
Compounds with the same structural formula but a different arrangements of atoms in space
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Stoichiometry
The molar relationship between the relative quantities of substances taking part in the reaction
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Stratosphere
The second layer of the Earth's atmosphere containing the "ozone layer" about 10km to 50km above the Earth's surface
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Structural Formula
A formula showing the minimal detail for the arrangement of atoms in a molecule
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Structural Isomer
Compounds with the same molecular formula but a different structural formula
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Sub-shell
A group of the same type of atomic orbitals (s,p,d or f) within a shell
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Substitution Reaction
A reaction in which an atom or group of atoms is replaced with an atom or group of atoms
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Sucessive Ionisation Energy
A measure of the energy required to remove each electron in turn eg. the third ionisation energy is the energy required to go from 2+ to 3+
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Termination
The end step of radical substitution when two radicals combine to form a non-radical molecule
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Thermal decomposition
The breaking up of a chemical substance with heat into at least two chemical substances
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Troposphere
The lowest layer of the Earth's atmosphere, extending from the Earth's surface up to about 7km (above the poles) and to about 20km (above the tropics)
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Unsaturated hydrocarbons
A hydrocarbon containing carbon-carbon multiple bonds (normally double)
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van der Waals Forces
Very weak attractive forces between induced dipoles in neighbouring molecules
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Volatility
The ease that a liquid turns into a gas. Volatility increases as boiling point decreases
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Water of crystallisation
Water molecules that form an essential part of the crystalline structure of a compound
