reaction rates chem

• Increasing the temperature increases the rate of reaction. As increasing temperature increases the kinetic energy of particles, so they collide more frequently and energetically.
• Increasing pressure in reacting gases increases the rate of reaction, as it increases the number of particles in a given volume so increases the frequency of collisions
• Increasing concentration of reacting solutions increases the rate of reaction, as it increases the number of particles in a given volume and so increases the frequency of collisions.
• Increasing the surface area of solid reactants increases the rate of reaction, as it increases the frequency of collisions so increases the rate of reaction
• Quantity of reactant or product can be measured by the mass in grams or by a volume in cm3

  Units of rate of reaction may be given as g/s or cm3/s
• to measure product formed: if the product is a gas, you can measure the volume of gas produced in a gas syringe
• Explain how reactions occur when particles collide and that rates of reaction are increased when the frequency and/or energy of collisions is increased :

  Chemical reactions only occur when the reacting particles collide with enough energy, the minimum amount of energy required is called the activation energy.

  in order to increase the rate of a reaction, you need to increase the frequency/energy of collisions, so that more of them reach the activation energy

  this can be done by: increasing temperature, pressure, concentration, surface area or by using a catalyst
• Interpret graphs of mass, volume or concentration of reactant or product against time :

  To find the rate of reaction graphically Draw tangents to curves and use the slope of the tangent as a measure of the rate of reaction

  Gradient = rate of reaction, a steeper line means a greater increase/decrease in rate

  Remember to check if the graph is showing you a product or a reactant- for a product you would be expecting the mass/volume/concentration to increase, whereas for a reactant you would be expecting the mass/volume/concentration to decrease
• Describe a catalyst as a substance that speeds up the rate of a reaction

  without altering the products of the reaction, being itself unchanged

  chemically and in mass at the end of the reaction:

  Catalysts are substances that speed up chemical reactions without being changed or used up during the reaction. They are the same and have the same mass at the end of the reaction.
• Explain how the addition of a catalyst increases the rate of a reaction in terms of activation energy :

  *Catalysts decrease the activation energy; this increases the proportion of particles with energy to react, leading to more frequent successful collisions and so an increased rate of reaction

  *Catalysts lower the activation energy by providing a different pathway for a chemical reaction that has a lower activation energy.
• Enzymes act as catalysts in biological systems

  * Yeast is the enzyme used in the production of ethanol as it is fermented from sugars, ethanol is in alcoholic drinks