Rates of reaction

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  • Created by: Holly45
  • Created on: 13-03-15 17:40

Energy transfer

  • exothermic reaction is when energy is transferred to its surroundings usually in the form of heat
  • neutralisation reactions are also exothermic
  • an endothermic reaction is when energy is taken in from its surroundings
  • thermal decomposition is an endothermic reaction
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Collision theory and catalysts

  • increasing temperature causes faster collisions
  • the minimum amount of energy needed by the particles to react is known as the activation energy
  • a catalyst speeds up a reaction without being changed
  • different reactions need different catalysts
  • catalysts are expensive
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Collision theory

  • more collisions will increase the rate of reaction
  • an increase in temperature makes the particles move quicker
  • a more concentrated solution means more reactant particles and water molecules colliding
  • in a gas, increasing the pressure means the particles are squeezed together so more frequent collisions will occur
  • a larger surface area means more frequent collisions
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Experiments

THIOSULFATE AND HCL:

  • 2 chemicals are both clear solutions
  • react together to form a yellow precipitate of sulphur
  • higher temperature quicker reaction
  • black mark to disappear through the cloudy sulphur and timing how long it takes

HYDROCHLORIC ACID AND MARBLE CHIPS

  • gas syringe and take readings at regular intervals
  • repeat the experiment with exactly the same volume of acid, and exactly the same mass of marble chips but more crushed up
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Measuring the rate of reaction

  • can be measured by either how quickly the reactants are used up or how quickly the products are formed
  • rate of reaction = amount of product formed/reactant used (divided by) time

PRECIPITATION:

  • measure how long it takes for a mark to dissapear
  • clouds the solution
  • people disagree the exact point at which the cross disappears

CHANGE IN MASS:

  • the quicker the reading on the balance drops the faster the reaction
  • most accurate

VOLUME OF GAS GIVEN OFF:

  • the more gas given off during a given time interval, the faster the reaction
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