CHEMISTRY DEFINITIONS

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  • Created by: Beanie10
  • Created on: 07-10-19 18:05
Isotope
Atoms of the same element with a different amount of neutrons and the same amount of protons
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Relative isotopic mass
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12
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Relative atomic mass
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12
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Molecular formula
The actual number of atoms of each element in a molecule
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Empirical formula
The simplest whole number ratio of atoms of each element in a compound
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Relative molecular mass
Compares the mass of a molecule with the mass of an atom of carbon-12
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Standard solution
A solution of a known concentration
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Strong acid
A strong acid only releases all its H+ ions and completely dissociates in aqueous solutions
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Weak acid
A weak acid only releases a small proportion of its H+ ions into solution and only partially dissociates in aqueous solution
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Base
A base neutralises an acid to form a salt
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Alkali
An alkali is a base that dissolves in water releasing OH- ions into the solution
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Oxidation Number
A measure of the number of electrons that an atom uses to bond with atoms of another element
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Orbitals
An atomic orbital is a region around the nucleus that can hold up to two electrons, with opposite spins.
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Ionic bonding
The electrostatic attraction between positive and negative ions.
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Covalent bonding
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
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Dative covalent bond
A covalent bond i which the shared pair of electrons has been supplied by one of the bonding atoms only
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Average bond enthalpy
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
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Electronegativity
The ability of an atom to attract electrons in a covalent bond
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Intermolecular forces
Weak interactions between dipoles of different molecules
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Periodicity
A repeating trend in properties of the elements across each period of the periodic table
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First ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
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Second ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
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Disproportionation
A type of redox reaction in which the same element is both oxidised ad reduced
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Enthalpy
A measure of the heat energy in a chemical system
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Activation energy
The minimum amount of energy required for a reaction to take place
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Standard enthalpy change of reaction
The enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states
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Standard enthalpy change of formation
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements under standard conditions, with all reactants and products in their standard states
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Standard enthalpy change of combustion
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states
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Standard enthalpy change of neutralisation
The energy change that accompanies the reaction of a acid by a base to form one mole of H2O, under standard conditions
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Specific heat capacity
The energy required to raise the temperature of 1g of a substance by 1K.
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Hess' law
States that if a reaction can take place by two routes, and the starting and finishing conditions are the same, the total enthalpy change is the same for each route.
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Catalyst
A catalyst is a substance that changes the rate of a chemical reaction without undergoing any permanent change itself.
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Homogeneous catalyst
Has the same physical state as the reactants.
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Heterogeneous catalyst
Has a different physical state from the reactants.
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Le Chateliers Principle
States that when any change made to a system in equilibrium , the system will shift to oppose the change.
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Hydrocarbon
A compound containing carbon and hydrogen only
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Saturated hydrocarbon
A hydrocarbon with single bonds only.
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Unsaturated hydrocarbon
A hydrocarbon that contains carbon to carbon multiple bonds.
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Homologous series
A series of organic compounds with similar chemical properties whose successive members increase by -CH2.
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Functional group
A functional group is the part of the organic molecule that is largely responsible for the molecules chemical properties.
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Aliphatic
Carbon atoms are joined to each other in unbranched (straight) or branched chains
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Alicyclic
Carbon atoms are joined to each other in ring (cyclic) structures
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Aromatic
some or all of the carbon atoms are found in a benzene ring
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Displayed formula
Shows the relative positioning of all the atoms in a molecule and the bonds between atoms.
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Structural formula
Uses the smallest amount of detail necessary to show the arrangement of atoms in a molecule
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Skeletal formula
Simplified organic formula.
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Structural isomers
COmpounds with the same molecular formula but a different structural formula.
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Homolytic fission
When a covalent bod breaks by homolytic fission, each of the bonded atoms takes one of the shared pair of electrons from the bond
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Radical
An species with an unpaired electron
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Heterolytic fission
Whe a covalent bond breaks by heterolytic fission, one of the boded atoms take both of the electrons from the bond
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Curly arrows
The movement of a electron pair
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SIgma bond
Where each carbon atom in an alkane is joined to four other atoms by single covalent bonds
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Covalent bond
A shared pair of electrons
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Stereoisomers
Have the same structural formula but a different arrangement of the atoms in space.
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Polymer
Large molecules formed from many repeat units of smaller molecules known as monomers
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Hydrolysis
A chemical reaction involving water or an aqueous solution of a hydroxide that causes the breaking of a bond in a molecule
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Fragmentation
Whe molecular ions break down into smaller pieces, known as fragments, in a mass spectrometer
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Half life
The time taken for half of a reactant to be used up.
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Rate determining step
The slowest step in the reaction mechanism of a multi-step reaction
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Homogeneous equilibrium
Contains equilibrium species that all have the same state or phase.
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Heterogeneous equilibrium
Contains equilibrium species that have different states or phases.
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Mole fraction
The mole fraction of a gas is the same as its proportion by volume to the total volume of gases in a gas mixture
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Partial pressure
The partial pressure of a gas is the contribution that the gas makes towards the total pressure
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Bronsted-Lowry acid
A proton donor
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Bronsted-Lowry base
Proton acceptor
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Conjugate acid-base pair
Contains two species that can be interconverted by transfer of a proton
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Monobasic acid
Has one H+ ion that can be replaced per molecule in an acid-base reaction
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Dibasic acid
Has two H+ ions that can be replaced per molecule in acid-base reactions
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Tribasic
Has three H+ ions that can be replaced per molecule in acid-base reactions
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Buffer solution
A system that minimises pH changes when small amounts of an acid or base are added
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Lattice entahlpy
A measure of the strength of ionic bonding in a giant ionic lattice
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Standard enthalpy change of atomisation
The enthalpy change that takes place for the formation of one mole of gaseous atoms from the element in its standard state under standard conditions
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The first electron affinity
The enthalpy change that takes place when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions
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The standard enthalpy change of solution
The enthalpy change that takes place when one mole of a solute dissolves in a solvent
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The standard enthalpy change of hydration
The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions
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Entropy
Used for the dispersal of energy and disorder within the chemicals making up the chemical system
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Standard entropy
The standard entropy of a substance is the entropy of one mole of a substance, under standard conditions
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Other cards in this set

Card 2

Front

The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Back

Relative isotopic mass

Card 3

Front

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Back

Preview of the back of card 3

Card 4

Front

The actual number of atoms of each element in a molecule

Back

Preview of the back of card 4

Card 5

Front

The simplest whole number ratio of atoms of each element in a compound

Back

Preview of the back of card 5
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