Definitions of AS Chemistry unit 2 0.0 / 5 ? ChemistryKey wordsASAQA Created by: sarahbrennan98Created on: 25-04-15 18:30 Enthalpy Change The change in heat energy under constant pressure 1 of 33 Standard conditions 100kPa and 298K 2 of 33 Exothermic reactions Heat is given out by particles (Exo = Extra) 3 of 33 Endothemic reactions Heat is taken in by the particles (Endo = End of heat) 4 of 33 Standard Enthalpy of Formation The standard enthalpy change when one mole of a compound is formed from its elements under standard condidtions 5 of 33 Standard Enthalpy of Combustion The standard enthalpy when on emole of a compound is burned completely in oxygen under standard condidtions 6 of 33 Activation energy The minimum amount of energy needed for collisions to be succesful 7 of 33 Collision Frequency Number of collisions between particles per second 8 of 33 Collision Energy Combined kinetic energy of colliding particles 9 of 33 Rate of Reaction Change in concentration per unit of time 10 of 33 Catalyst A substance that increases the rate of reaction without chemically being changed itself 11 of 33 Dynamic Equalibrium A reaction where both the forward and backward reactions occur at the same rate, with the same concentration of products and reactants 12 of 33 Le Chateliers principle When a reaction at equilibrium is changes, the system changes in order to counter-balance this change and regain equalibrium 13 of 33 Oxidation Loss of electrons 14 of 33 Reduction Gain of electrons 15 of 33 Oxidizing agent Electron acceptor 16 of 33 Reducing agent Electron donor 17 of 33 Oxidation number charge that would occur on an atom if the bonding were completely ionic 18 of 33 Redox reaction Electrons are transferred from on species to another 19 of 33 Geometrical isomerism The same molecular formula but different structural arrangement around a double bond 20 of 33 Addition Combination of 2 or more molecules to for a single molecule 21 of 33 Substitution Replacement of one atom/group of atoms by another 22 of 33 Elimination Loss of a small molecule from a larger molecule to form an unsaturated compound 23 of 33 Electriphile Species which can accept an electron pair from a different species 24 of 33 Nucleophile Species wich can use a lone pair of electrons to form its covalent bond in substitution or elimination 25 of 33 Free Radical Species with a free unpaired electron 26 of 33 Homolytic Fission Breaking of a covalent bond in a way that one electron goes to each atom 27 of 33 Heterolytic Fission Breaking of a covalent bond in a way that both electrons go to the sae atom 28 of 33 Hydration Addition of water 29 of 33 Hydrolysis Addition of water to break a covalent bond 30 of 33 Oxidation Addition of oxygen or removal of hydrogen 31 of 33 Polymerisation Combination of a large number of monomers to form a single chain 32 of 33 Biofuel A fuel produced from a renewable source 33 of 33
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