COLLISION THEORY

• The rate of a chemical reaction is proportional to the number of collisions between reactants molecules.
• All substances are comprise of millions of tiny particles in constant motion, these particles are constantly colliding.
• Not all collision between particles of reactants result to generation of a product.
• Two factors that determine weather a reaction will occur:

  1. Substances or particles of reactants must physically collide with enough kinetic energy.
  2. Substances or particles must come into contact or collide in the correct orientation, so that their electrons shells can rearranged to form a product of the reaction.
• A chemical reaction does not take place if collision between molecules does not have sufficient energy to break the bonds in the reactants and if the molecules are not properly oriented.
• Rate of Reaction

  • How fast a reaction occured.
  • Different for every reaction.
• Higher pressure, forces the particles closer together. More chances of particles colliding and reacting.
• Increasing the pressure decreases the volume and increases the concentration. The molecules have less space to move in an are more likely to collide.
• It refers to the average kinetic energy of particles in an object.

  Temperature
• As a rule of thumb, a rise in temperature of 10°C doubles the reaction rate.
• As the temperature rises, collision becomes frequent due to high kinetic energy or faster movements of molecules resulting to build up more energy.
• It refers to the measures of how much solute is the dissolved in a solvent to form a homogeneous mixture.

  Concentration
• A higher concentration, higher number of solute, more molecules of reactants, hence higher chance of collision, higher or faster reaction rate.
• It refers to how much exposed area a solid object has.

  Surface Area
• Surface area is express in square units.
• The more finely divided a solid is, the faster the reaction rate. Likewise, powdered solid has greater surface area, thus the particles have higher chance of colliding.
• The chemical nature of reactants is a factor affecting the rate of reaction because some reactions are more or less reactive than others.
• Mnemonic for reactivity series:

  Please

  Stop

  Calling

  Me

  A

  Careless

  Zebra

  Instead

  Try

  Learning

  How

  Copper

  Saves

  Gold
• Reactivity Series:

  Potassium (Most Reactive)

  Sodium

  Calcium

  Magnesium

  Aluminum

  Carbon

  Zinc

  Iron

  Tin

  Lead

  Hydrogen

  Copper

  Silver

  Gold (Least Reactive)
• Substance which speeds up a reaction, What is chemically unchange at its end.

  Catalyst
• When the reaction has finished, the mass of catalyst is the same as at the beginning.
• Catalyst provides alternative route for the reaction, with a lower activation energy and higher reaction rate.
• A reaction which involves a catalyst in their system.

  Catalytic Reaction
• Characteristic Feature of Catalyst:

  • It does not initiate a chemical reaction.
  • It is not consume in the reaction.
  • It tend to react with reactants.
• A type of catalyst which increases the reaction rate and lowers the activation energy.

  Positive Catalyst
• A type of catalyst which decreases the rate of reaction and increases the activation energy.

  Negative Catalyst
• It is the term refers to the product of a chemical reactions that acts as a catalyst.

  Auto Catalyst
• Auto catalyst facilitates auto catalyzed reaction.
• A substance that influences the speed of chemical reaction which is not possible under ordinary conditions.

  Induced Catalyst