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2p9 reaction rates 191110

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Reaction rates. S2:

Reaction rates. S2:
Chemical reactions
effect of particle size on reaction rates

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2p9 reaction rates 191110 2p9 reaction rates 191110 Presentation Transcript

  • Rates of reactions 2P9: Friday 19 th November
  • How do chemical reactions happen?
    • When particles collide / bump together, they can react and become chemically joined. This is how chemical reactions happen.
  • Chemical reactions can occur at different speeds Reaction SLOW MEDIUM FAST Oil forming Firework Exploding Logs burning Frying an egg
  • Experiment
    • Aim : To see what effect the particle size has on the speed of a chemical reaction.
  • Weigh marble chips/powder
    • Put a piece of filter paper on the top of your balance and turn on
    • Measure out approximately 2g of marble chips – put to side for your experiment
    • Using a new piece of filter paper on the scales:
    • Measure out the same weight of the powdered calcium carbonate (chalk powder) using the spatula onto the filter paper
  • Method: Collect 2 small beakers and fill each with 25cm3 of hydrochloric acid. Add the calcium carbonate to each beaker as shown above. Observe and record what happens.
    • Results:
    • The calcium carbonate powder reacted faster than the lumps.
    • WHY???
    • A quick explanation:
      • Imagine you had a square which would be like a large particle. The other particle would only be able to hit off 4 sides - there is a small surface area.
    • Watch the animation which follows…
  • a SLOW reaction
    • If we break the large square up into many smaller squares (smaller particle size) then there are many more surfaces for the other particle to hit, increasing the chance of a chemical reaction…
    • Watch the following animation…
  • a FAST reaction
  • Conclusion
    • The smaller the particle size, the faster the speed of the reaction
    • When the particles are smaller, there is a greater surface area of the solid exposed to the acid. More of the particles are able to collide and so the reaction happens faster.