Catalysts-

• A catalyst is a substance that:

  • Increases the rate of a reaction
  • Does not alter the products of the reaction
  • Is unchanged chemically and in mass at the end of the reaction
• Only a very small mass of catalyst is needed to increase the rate of a reaction
• Not all reactions have suitable catalysts
• Catalysts only affect the rate of reaction, not the yield of the reaction
• A catalysed reaction produces the same amount of product as an uncatalysed reaction but at a faster rate
• Different substances catalyse different reactions
• Catalysts are transition metals or compounds of transition metals
• How catalysts work:

  • A catalyst provides an alternative reaction pathway with a lower activation energy than the uncatalysed reaction
  • This does not change the frequency of collisions but increases the frequency of successful collisions because more collisions exceed this lower activation energy
• The effect of a catalyst on the activation energy is shown on a reaction profile chart, illustrating how the energy of the reactants and products change during a reaction
• Enzymes:

  • Enzymes are biological catalysts important for controlling reactions in cells and in industry
  • The use of enzymes allows some industrial reactions to occur at lower temperatures and pressures than traditionally needed
• Yeast is a single-celled fungus

  • The enzymes in yeast are used to produce wine, beer, and other alcoholic drinks through fermentation of sugars