36. Increasing the Surface Area of a Solid. A solid in a solution can only react when particles collide with the surface. The bigger the area of the solid surface, the more particles can collide with it per second A powder has the largest surface area and will have the fastest reaction rate.
37. THE EFFECT OF SURFACE AREA ON REACTION RATES a reaction between magnesium metal and a dilute acid like hydrochloric acid. Increasing the number of collisions per second increases the rate of reaction.
40. What affects the rate of a reaction? 2. Temperature Increasing temperature will increase energy in the particles leads to an increased probability of favourable collisions .
42. 3. Concentration and Pressure Increasing concentration or pressure increases the rate of a reaction, because the particles are closer together and have an increased probability of favourable collisions. What affects the rate of a reaction?
50. 4. Catalyst Often a catalyst is there to provide a favourable surface for a reaction to take place What affects the rate of a reaction? The black object represents the catalyst
52. Examples CATALYSTS ON REACTION RATES Reaction catalyst Decomposition of hydrogen peroxide Manganese (IV) oxide, MnO 2 Manufacture of ammonia by the Haber Process Iron Contact Process to make sulphuric acid Vanadium (V) oxide, V 2 O 5
54. 4. Catalyst How does a catalyst work? 1) A catalyst provides a surface on which the reaction can take place. This increases the number of collisions between the particles of the substances that are reacting. What affects the rate of a reaction?
57. 4. Catalyst How does a catalyst work? 2) A catalyst lowers the activation energy This means that the particles can react with less energy than they needed before the catalyst was added. (Think about it: if the government lowered the legal age to buy cigarettes , then more people could legally buy cigarettes. Similarly, if we lower the amount of energy needed for particles to react, then more particles can react ). What affects the rate of a reaction?
58. A catalyst provides an alternative route for the reaction. That alternative route has a lower activation energy. Activation energy