Collision theory

Reactions happen if particles collide, so if you increase the number of collisions, the reaction happens more quickly. there are 4 factors that all lead to more collisions:
1. Temperature, concentration, the presence of a catalyst and the size of the particles
Temperature
1. Increasing the temperature means the particles are going faster and have more energy
  1. If the temperature is increased: the reactant particles move more quickly they have more energy the particles collide more often, and more of the collisions result in a reaction the rate of reaction increases
  2. Higher temperatures also increase the energy of the collisions since the particals are moving faster. reactions only happen if the particles collided with enough energy. at a higher temperature there'll be more particles colliding with enough energy to make the reaction happen.
Concentration
1. Increasing the concentration ( or pressure ) means the particles are more crowded together
  1. If the concentration of a dissolved reactant is increased, or the pressure of a reacting gas is increased: the reactant particles become more crowded there is a greater chance of the particles colliding the rate of reaction increases
Size of particles
1. The rate of a chemical reaction can be raised by increasing the surface area of a solid reactant. This is done by cutting the substance into small pieces, or grinding it into a powder.
  1. Smaller solid particles ( or more surface area) means other particles can get to it more easily
2. If a solid reactant is broken into small pieces or ground into a powder: its surface area increases more particles are exposed to the other reactant there are more collisions the rate of reaction increases
  1. For Example : calcium carbonate + hydrochloric acid = calcium chloride dioxide + water
    1. Calcium carbonate is the chemical name for marble, you can change the surface area by breaking large marble chips into small chips
3. Fine powders of combustion materials dispersed in the air burn very very fast because they have such a big surface area, if they spark they will explode
  1. Explosions are very fast reactions in which a lot of gaseous product is released very quickly. For example: burning hydrogen explosions from TNT or dynamite
Catalysts
1. A catalyst is a substance that can increase the rate of a reaction, without being chemically changed or used up in the reaction, and because it isn't used up you only need a tiny bit of it to catalyst large amounts or reaction
2. Catalyst are very specific, they only work in certain reactions
  1. eg: iron, making ammonia from nitrogen and hydrogen
3. A catalyst works by giving the reaction particles a surface to stick to where they can bump into each other, and reduces the energy needed by the particles before they react.
  1. The number of collisions is NOT increased but there are just more successful collisions

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Collision theory

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