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Rates of reactions. State how the rates of chemical reactions of kitchen chemicals are effected by; concentration, particle size, temperature, mixing, catalysts . Reactions:. For a reaction to occur there must be at least 2 chemicals present.

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Rates of reactions

Rates of reactions

State how the rates of chemical reactions of kitchen chemicals are effected by; concentration, particle size, temperature, mixing, catalysts


Reactions
Reactions:

  • For a reaction to occur there must be at least 2 chemicals present.

  • The chemicals need to come in contact with one another and have enough energy to react.

  • The reaction rate is how fast a reaction happens. Reactions can be sped up or slowed down.

    A + B -> C + D

  • In a reaction the starting chemicals are called reactants (A & B)

  • The new chemicals are called products (C & D)

  • We can measure how quickly a substance is used up (e.g. marble chip dissolves)

  • Or how quickly new substances are formed (e.g. gas) 


Concentration
concentration

  • The higher the concentration, the faster the reaction goes.

  • Concentration: how strong a chemical is.

  • The more concentrated a chemical is the more particles it has.

  • With more particles in the same space there is an increase in the number of collisions.


Mini experiment
Mini Experiment

  • Aim: to compare the rate of reaction between 2 different concentrations of acid and Mg metal

  • Method:

    Collect: 2 molL-1 acid and 0.5 molL-1 acid, 2 test tubes, 2 pieces of Mg metal, 10mL measuring cylinder, glasses

    • accurately measure 3mL 0.5 molL-1 acid, and place in one test tube

    • accurately measure 3mL 2 molL-1 acid, and place in another test tube

    • Place 1 piece of Mg metal into the first test tube and time how long it takes until the reaction stops.

    • Repeat using the 2nd test tube (2 molar).


  • Results:

    • 0.5 molL-1 acid time: _______________

    • 2 molL-1 acid time: ________________

    • Fastest one was the ___________

  • Conclusions:

    • The ___________ acid was fastest because it is __________ concentrated. It had a lot _________ acid particles in it.

  • Equation: copy from the whiteboard


Particle size
Particle size:

  • The collisions in a reaction only occur on the exposed surface area of a solid.

  • The more particles that are exposed, the more collisions that can occur.


Mini experiment1
Mini experiment:

  • Aim: to compare the reaction between a small surface area and large surface area

  • Method:

    • Collect: 2 test tubes, safety glasses, 2 molL-1 acid, 1 large marble chip, equivalent amount of powdered marble chip, 2 10 mL measuring cylinders.

    • Add the large marble chip to one test tube and the powdered to the other.

    • Accurately measure 3mL of acid and place into each test tube at the same time.

    • Record what happens? Write down all you see and hear, compare the 2 test tubes.


  • Results:

    • Chip: ___________________________________________ ________________________________________________

    • Powdered: _______________________________________ ________________________________________________

    • The difference: ___________________________________ ________________________________________________

  • Conclusion:

    • The ______________ was more …..

  • Equation: copy from the whiteboard


Rates of reaction temperature
Rates of reaction: temperature

  • When the temperature is increased, the particles move faster.

  • Because they move faster, there is an increased chance of collisions.

  • Because they have more energy, the collisions have more energy also and so they are more likely to react.


Rates of reaction mixing
Rates of reaction: Mixing

  • When you mix something, the particles are moved around one another and so there is an increased chance of reacting.

  • E.g. sugar in a cup of coffee, without mixing (stirring) the sugar will dissolve eventually, but with mixing it only takes a couple of seconds to dissolve


Rates of reaction catalyst
Rates of reaction: Catalyst:

  • A catalyst speeds up a reaction but doesn’t take part in the reaction.

  • It works by lowering the amount of energy needed for a reaction to occur.

  • This means that the particles don’t have to collide with the same amount of energy as with no catalyst.


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