Definitions for aqa unit 2 chemistry 0.0 / 5 ? ChemistryAllASAQA Created by: ClareCreated on: 09-05-14 09:16 Enthalpy Change Change in heat energy under constant pressure. 1 of 32 Standard Conditions 100kPa and a stated temperature, usually 298K/25 C 2 of 32 Exothermic A change during which heat is given out by particle. 3 of 32 Endothermic A change in which heat is absorbed by particles. 4 of 32 Standard Enthalpy of Formation Heat energy change when one mole of a compound is formed from its elements in their standard states under standard conditions. 5 of 32 Standard Enthalpy of Combustion Heat energy change when one mole of a substance is completely burned in excess oxygen under standard conditions. 6 of 32 Activation Energy The minimum energy required for a collision to be successful. 7 of 32 Collision Frequency The number of collisions between particles per second. 8 of 32 Collision Energy The combined kenetic energy of colliding particles. 9 of 32 Rate of Reaction The change in concentration of a species per unit of time. 10 of 32 Catalyst A substance which increases the rate of a chemical reaction without itself being chemically change at the end of the reaction. 11 of 32 Dynamic Equilibrium A reaction in which the forward and reverse reactions are proceeding at the same rate, so the concentrations of reactants and products are constant 12 of 32 Le Chatelier's Principle If a change in conditions is imposes on a system at equilibrium, the system will react in such a way as to oppose the effect of the change. 13 of 32 Oxidation Loss of elections OR the addition of oxygen OR the removal of hydrogen 14 of 32 Reduction Gain of electrons 15 of 32 Oxidising agent Electron acceptor 16 of 32 Reducing Agent Electron Donor 17 of 32 Oxidation Number The charge that would be on an atom if the bonding were completely ionic. 18 of 32 Redox Reaction A reaction in which electrons a transferred from one species to another. 19 of 32 Geometric Isomerism The same molecular formula, but a different spatial arrangement of atoms around a double bond. 20 of 32 Addition Combination of two or more molecules to form a single molecule. 21 of 32 Substitution Replacement of one atom or group of atoms by another 22 of 32 Elimination Loss of a small molecule from a larger one to form an unsaturated compound. 23 of 32 Electrophile Species which can accept an electron pair from another species. 24 of 32 Nucleophile Species which can use a lone pair of electrons to form a covalent bond. 25 of 32 Free Radical Species with an unpaired electrons 26 of 32 Homolytic Fission Breaking of a covalent bond in such a way that one electron goes to each atom 27 of 32 Heterolytic Fission Breaking of a covalent in such a way that both electrons go to the same atom 28 of 32 Hydration Addition of water to a species 29 of 32 Hydrolysis Use of water to break covalent bonds 30 of 32 Addition Polymerisation Combination of a large number of monomers to form a single chain 31 of 32 Biofuel A fuel derived of produced from renewable biological sources 32 of 32
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