Chemistry C2 GCSE AQA - Unit 4 Follow up to units 1, 2 and 3 3.5 / 5 based on 3 ratings ? ChemistryGCSEAll boards Created by: OneTooManyAnOpinionCreated on: 23-05-12 17:35 How Fast? Rate= amount of reactant used / time OR Amound of product formed / time This equals the RATE OF REACTION 1 of 5 Collision Theory States reactions only happen if particles COLLIDE The particles must collide with enough ENERGY to change into NEW SUBSTANCES Minimum energy needed is called the ACTIVATION ENERGY Factors that increase this are TEMPERATURE CONCENTRATION / PRESSURE SURFACE AREA of solids Use of a CATALYST 2 of 5 Effect of Temperature 3 of 5 Effect of Concentration 4 of 5 Effect of a Catalyst Catalysts change the rates of chemical reactions Most used to SPEED UP reactions Catalyst is left at the end of the reaction so it can be REUSED Work by LOWERING the ACTIVATION ENERGY Means MORE collisions in a reaction Most expensive, but ECONOMICAL - they do not need replacing often 5 of 5
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