Unit Two: Collision Theory Flashcards
What’s collision theory?
Collision theory says that the rate of a reaction simply depends on how often and how hard the reacting particles collide with each other (particles have to collide in order to react)
What increases collisions? (3)
What increases rate of reaction? (1)
Higher temperature
Higher concentration (or pressure)
Larger surface area
Faster collisions
Higher temperature:
When the temperate is increased the particles move quicker —> if they’re moving quicker, they’re going to collide more often
Higher concentration (or pressure):
If a solution is made more concentrated it means there are more of reactant knocking about between the water molecules which makes collisions between the important particles more likely
In a gas, increasing the pressure means the particles are more squashed up together so there will be more frequent collisions
Larger surface area:
If one of the reactants is a solid then breaking it up into smaller pieces will increase the total surface area. This means the particles around it in the solution will have more area to work on, so there’ll be more frequent collisions
How do catalysts reduce costs in industrial reactions?
- Increase rate of reaction-saves money because the plant doesn’t need to operate for as long
- Catalysts allow reactions to work at lower temperatures-reduces energy costs & saves money
Disadvantages to catalysts:
- Expensive to buy
- Different reactions need different catalysts-have to buy different catalysts
- Catalysts can be poisoned by impurities, so they stop working
What is an exothermic reaction?
Exothermic gives out energy to the surroundings, usually in the form of heat
Examples of exothermic reactions:
Burning fuels (combustion)
Neutralisation reactions
Oxidisation reactions
What is an endothermic reaction?
Endothermic reactions take energy in from the surroundings, usually in the form of heat
Example of endothermic reaction:
Thermal decomposition
