9b - Rate of Reactions Student Notes PDF

6.2 - Factors Affecting the Rate of Chemical Reactions Rate of reaction refers to… how quickly or slowly the reactants turn into products The rate of a chemical reaction can be sped up or slowed down. reaction...

6.2 - Factors Affecting the Rate of Chemical Reactions Rate of reaction refers to… how quickly or slowly the reactants turn into products The rate of a chemical reaction can be sped up or slowed down. reaction rate high a rxn. that happens quickly has ________________________ ex. detonation of explosives low reaction rate a rxn. that happens slowly has ________________________ a ex. the rusting of a bicycle chain Collision Theory For a reaction to take place, the particles of the substances that are reacting have to collide. If they collide with a sufficient amount of energy, then they will react. amount of Kinetic energy that Activation energy is…the minimum need if they are going to react (ie for bonds two particles. in reactants to be broken) when they collide 2 main ways of increasing the rate of a reaction: 1) increase the number of collisions that more collisions kinetic Energy so 2) increase the amount of reaction lead to a Four Main Factors Affect the Rate of Chemical Reactions 1) tempature 3) surface area of reactions 2) concentration of reactants 4) presence of a catalyst/ Temperature an inhibitor Temperature is a measure of the average KE of all of the particles in a sample of matter. When particles have more energy they move around more, collide more frequently with other particles, and therefore….. chemical cause reactions to happen faster The rate of reaction changes with temperature: increasing temperature = _______________ increasing reaction rate decreasing reaction rate decreasing temperature = _______________ Concentration dissolved in a certain solute is Concentration refers to…how much volume of solution – concentration is measured in mass per unit volume (g/L) – concentration of a substance can change if it is in aqueous solution or in the gaseous state Usually, the higher the concentration of reactants, the faster the reaction occurs. unit volume in high concentrations - Since there are more molecules per there are more opportunities for molecules to collide and react  Surface Area ….. is a measure of how much area ofan object is exposed - ↑ many small particles For the same mass, _______________________________________ have a greater total surface area one large particle than the _______________________________________ does. Chemical reactions occur when and where particles collide. o The more particles there are to collide, the higher the reaction rate. Increases Increasing surface area _____________________________ the rate of reaction. o since there are more particles exposed to each other, more reactions take place o surface area can be increased by __________________ to occur; (the surface area must also be exposed for a reaction is a powdermay m bestirred/blownintotheair Catalysts Sometimes increasing the temperature or concentration is not a safe or practical way to increase in a livingcll to increase the rate reaction rate. of ex. increasing the tempatuve harm the decomposition of glucose might the cell A catalyst is a substance that speeds up the rate of a chemical reaction without being consumed (used up) in the reaction. – catalysts often lower the activation energy – in the presence of a catalyst, reactant molecules are better aligned, so when they collide, a rxn. is more likely to take place rate is needed to increase the – only asmall amount of catalyst of rxn Enzymes are biological catalysts in living cells. – enzymes are specialised – very temperature-sensitive Salivary amylase is a digestive enzyme that helps speed the breakdown of starch molecules in the mouth not occur fast would Many chemical · living organisms rxns. in if it weren't to sustain life, enough at "normal" tempatures for enzymes ↑ -