A-level Chemistry key terms
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- Created by: Pepper Hall
- Created on: 04-06-18 09:01
Acid
A proton donor (Bronsted-Lowry) or an electron pair acceptor (Lewis).
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Acid derivative
An organic compound related to a carboxylic acid of formula RCOZ, where Z=-Cl,-NHR,-OR or -OCOR
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Activation energy
The minimum energy required by a particle to react. This is also the enthalpy change between the reactants and the transition state.
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Aldehyde
An organic compound with the general formula RCHO.
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Alkaline earth metals
Metals in group 2 of the periodic table.
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Alkane
A hydrocarbon containing only C-C and C-H single bonds.
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Allotropes
Pure elements which can exist in different physical forms (i.e. the atoms are arranged differently).
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Anaerobic respiration
The process that releases energy and forms new compounds in the absence of oxygen.
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Atom economy
This describes the efficiency of a chemical reaction. You divide the mass of desired product by the total mass of reactants, then multiply that by 100.
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Atomic orbital
A region of space around an atomic nucleus where there's a high probability of finding an electron.
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Avogadro constant
The total number of particles in one mole of a substance. = 6.022x(10^23).
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Base
A proton acceptor (Bronsted-Lowry) or an electron pair donor (Lewis).
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Base peak
The peak representing the ion of greatest abundance (i.e. the tallest peak) in a mass spectrum.
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Bond dissociation enthalpy
The enthalpy change required to break a covalent bond with all species in the gaseous state.
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Buffer
Asolution that resists change of pH when small amounts of acid or base are added or on dilution.
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Calorimeter
An instrument for measuring the heat chnges that accompany chemical reactions.
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Carbocation
A carbon with a positive charge.
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Carbon-neutral
A process in which the same amount of carbond dioxide is given out as taken in.
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Catalyst
Asubstance that speeds up a reaction without being used up in the process.
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Catalytic cracking
Using a catalyst to break long-chain hydrocarbons into shorter chain hydrocarbons
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Chelation
The process by which a monodentate ligand is replaces by a multidentate ligand in forming dative bonds to a transition metal.
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Chemical feedstock
Starting material for an industrial chemical process.
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Chiral
Describes a molecule that exists as 2 non-superimposable isomers.
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Chiral centre
An atom to which 4 different substituents are bonded.
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Co-ordinate bond
A covalent bond in which both the electrons in the bond come from one of the atoms forming the bond.
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Co-ordination number
Number of ligand molecules bonded to a metal ion.
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Covalent bonding
The sharing of electrons between 2 non-metal atoms.
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Delocalisation
The spreading of electrons over several atoms to help them bond together.
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Delocalised
Electrons spread over several atoms.
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Dipole-dipole force
An intermolecular force that is caused by the attraction between molecules with permanent dipoles.
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Displacement reaction
A reaction where an atome or group of atoms replaces another in a compund.
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Displayed formula
Formula that is drawn out to show each atom and bond.
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Disproportionation
When the oxidation state of some atoms of a certain element is different on each side of a reaction.
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Dynamic equilibrium
A situation in which the composition of a constant concentration reaction mixture doesn't change, as both forward and backward reactions are going at the same rate.
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Electron density
Probability of electrons being found in a certain volume of space.
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Electron pair repulsion theory
Explains the shapes of molecules. Pairs of electrons around a central atom repel each other and take up certain positions as far away from each other as possible.
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Electronegativity
The power of an atom to attract the electrons in a covalent bond.
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Electrophile
An electron-deficient atom/ion/molecule that attacks areas of high electron density in another reactant.
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Electrophilic addition
An electrophile attacking a C=C bond to saturate it.
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Electrostatic forces
Forces of attraction/repulsion between electrically charged particles.
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Elimination
A reaction where an atom or group of atoms is removed from a reactant.
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Empirical formula
Simplest whole number ratio of atoms of each element in a compound.
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Enantiomer
One pair of nonsuperimposable mirror image isomers.
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Endothermic
When heat is taken in during a reaction, giving a positive enthalpy change and causing the temperature to drop.
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End point
The point in a titration when the volume of reactant added causes a change in colour in the indicator.
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Enthalpy change
A measure of heat energy transferred when a chemical/physical change takes place at a constant pressure.
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Enthalpy diagrams
A diagram that shows enthalpy changes for reactions.
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Entropy
A numerical measure of disorder in a chemical system.
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Equilibrium mixture
The mixture of reactants and products formed when a reversible reaction proceeds in a closed container until no further change occurs and the backward and forward reactions go at the same rate.
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Equivalence point
The point in a titration at which the reaction is just complete.
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Exothermic
When heat is given out during a reaction, giving a negative enthalpy change and causing the temperature to increase.
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Fatty acid
A long chain carboxylic acid.
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Fingerprint region
The area of an IR spectrum below about 1500cm^-1. This is caused by complex vibrations of a whole molecule - these vibrations are molecule-specific.
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Fraction
A mixture of hydrocarbons within the same range of boiling points, which are collected through the fractional distillation of crude oil.
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Free radical
A highly reactive chemical species with an unpaired electron.
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Functional group
An atom or group thereof in an organic molecule which is responsible for the characteristic reactions of that molecule.
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Group
Vertical column of elements in the periodic table, all with the same outer electron arrangement
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Half equation
An equation showing the electrons transferred to/from one particular species in a redox reaction.
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Homologous series
A set of organic compounds containing the same functional group.
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Hydration
When water is added to something to cause a reaction.
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Hydrogen bonding
An intermolecular force in which a hydrogen atom interacts with a more electronegative atom (O, F, or N).
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Hydrolysis
A reaction of a compund/ion with water.
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Incomplete combustion
When there's not enough oxygen for all the carbon in the fuel to burn to carbon dioxide in a combustion reaction, therefore carbon monoxide and/or carbon (soot) are formed.
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Inductive effect
Electron releasing effect of alkyl groups.
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Ionic bonding
Electron/s being transferred from one atom to another, causing electrostatic forces of attraction between the opposing charges of the ion.
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Ionisation energy
The energy required to remove a mole of electrons from a mole of atoms/ ions in the gaseous state.
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Isomer
1 of 2+ compound with the same molecular formula but a different arrangement in space.
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Ketone
An organic compound with an R-group on either side of a carbon atom with a C=O bond.
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Lattice
A regular 3D arrangement of atoms/ions/molecules.
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Leaving group
In an organic substitution reaction, the leaving group is an atom or group thereof that's ejected from the starting material, normally taking an electron pair with it, thus forming a negative ion.
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Ligand
An atom/ion/molecule
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Lone pair
A pair of outer shell electrons that isn't involved in bonding
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Maxwell-Boltzmann distribution
Distribution of energies/speeds of the molecules in a gas/liquid.
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Mean bond enthalpy
The average value of the bond dissociation enthalpy for a certain type of bond taken from a range of different compounds.
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Metallic bonding
A bond caused by delocalised outer electrons from metal atoms being electrostatically attracted to the metal ions in the lattice holding it together.
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Mole
A quantity of a substance containing 6.022x10^23 atoms/molecules.
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Molecular formula
A fromula that tells you the actual number of atoms of each element in a molecule of a compound.
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Molecular ion
An ionised molecule of sample in mass spectrometry, which has not been broken up during its flight through the instrument.
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Monomer
A small molecule that combines with many other monomers to make a polymer.
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Nucleons
Sub-atomic particles in the nucleus of an atom (protons and neutrons).
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Nucleophile
An ion/group of molecules with a negative charge or partially negative area or a lone pair that takes part in an organic reaction by attackind electron-deficient areas in another reactant.
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Nucleophilic substitution
When a nucleophile attacks a positively charged carbon atom in a molecule, replacing one of the groups/ atoms attached to the carbon in the original molecule.
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Nucleus
The tiny positively-charged centre of an atom containing protons and neutrons.
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Optical isomers
Pairs of molecules that are non-superimposable mirror images.
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Order of reaction
The sum of the powers to which the concentrations of the species in a reaction are involved in the rate expression.
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Oxidation
When an atom/group of atoms loses electrons in a reaction.
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Oxidation state
Number of electrons lost/gained by an atom in compound compared to an uncombined atom.
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Oxidising agent
A reagent that takes electrons from another species.
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Percentage yield
Actual amount of product divided by the theoretical amount of product in a chemical reaction expressed as a percentage.
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Period
A horizontal row of elements in the periodic table.
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Periodicity
The regular recurrence of properties of elements along a row of the periodic table.
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pH
A scale for meausing acidity and alkalinity. = -log(H+)
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Polar
Describes a molecule in which the charge is unevenly spread, so that one area is more negatively charged than another.
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Polarised
Describes an atom/ion where the charge distribution around it is distorted from spherical.
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Positive inductive effect
The tendency of some atoms or groups thereof to release electrons via covalent bonds.
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Proton number
Same as the atomic number, it shows the number of protons in the nucleus of an atom.
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Protonated
Describes an atom/molecule/ion to which a proton has been added.
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Racemate
An optically inactive mixture of equal amounts of 2 optical isomers of a chiral compound.
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Rate constant
The constant of proportionality in the rate expression.
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Rate-determining step
The slowest step in the reaction mechanism.
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Rate expression
Mathematical expression showing how the rate of a chemical reaction depends on the concentrations of various chemical species involved.
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Reaction mechanism
The series of steps leading from reactants to products in a chemical reaction.
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Redox reaction
Reduction-oxidation reaction; describes reactions in which electrons are transferred from one species to another.
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Reducing agent
A reagent that adds electrons to another species.
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Reduction
When an atom or group thereof gains electrons.
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Relative atomic mass
Average mass of an atom divided by one twelfth of the mass of one atom of carbon-12.
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Relative formula mass
Average mass of an entity divided by one twelfth of the mass of one atom of carbon-12.
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Relative molecular mass
Average mass of a molecule divided by one twelfth of the mass of one atom of carbon-12.
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Saturated molecule
A compound containing only hydrogen and carbon, with only C-C and C-H bonds.
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Specific heat capacity
The amount of heat required to raise the temperature of 1g of substance by 1K.
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Spectator ions
Ions that don't get changed by a reaction because they don't actually play a part in it.
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Standard molar enthalpy of combustion
The enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants in standard states and conditions.
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Standard molar enthalpy change of combustion
The enthalpy change when 1 mole of substance is formed from its elements with all reactants being in standard states and conditions.
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Stereoisomer
Isomers with the same molecular formula and structure, but a different position of the atoms in space.
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Stoichiometry
Simple whole number ratios in which chemical species react.
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Strong acid
An acid that is fully dissociated into ions in solution.
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Strong nuclear force
The force that hold the subatomic particles in a nucleus together in a nucleus.
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Structural formula
A way of writing the formula of an organic compound in which the bonds aren't shown, but each carbon atom is written separately.
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Structural isomer
Isomers with the same molecular formula but a different structure.
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Thermochemical cycle
A sequence of chemical reactions that convert a reactant into a product.
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Triglyceride
An ester formed between glycerol and 3 fatty acid molecules.
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van der Waals force
A type of intermolecular force of attraction which is caused by instantaneous dipoles between atoms/molecules.
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Weak acid
An acid that is only slightly dissociated into ions in solution.
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Other cards in this set
Card 2
Front
An organic compound related to a carboxylic acid of formula RCOZ, where Z=-Cl,-NHR,-OR or -OCOR
Back
Acid derivative
Card 3
Front
The minimum energy required by a particle to react. This is also the enthalpy change between the reactants and the transition state.
Back
Card 4
Front
An organic compound with the general formula RCHO.
Back
Card 5
Front
Metals in group 2 of the periodic table.
Back
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