<Li> The presence or absence of a catalyst . Catalysts are substances which change the pathway ( mechanism ) of a reaction which in turn increases the speed of a reaction by lowering the activation energy needed for the reaction to take place . A catalyst is not destroyed or changed during a reaction , so it can be used again . </Li>
<Li> The presence or absence of a catalyst . Catalysts are substances which change the pathway ( mechanism ) of a reaction which in turn increases the speed of a reaction by lowering the activation energy needed for the reaction to take place . A catalyst is not destroyed or changed during a reaction , so it can be used again . </Li>
it refers to a substance that speeds up chemical reactions
it refers to a substance that speeds up chemical reactions
catalyst
catalyst