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Collision Theory (Presence of a Catalyst (Enzymes are biological catalysts…
Collision Theory
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Surface Area
By increasing the total surface area of the reactants, we can increase the rate of reaction
An increased surface area mean that there are more exposed particles able to collide, increasing the chance of a collision
When reacting large lumps of solids in solution, only the particles at the surface of the solid are in contact with the solution and able to react, the particles at the centre of the solid must wait until other particles have reacted. When reacting a powdered solid in solution, much more of the particles are able to react as each tiny lump of solid is completely surrounded by solution, so there are many more exposed particles
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Temperature
Increasing temperature always increases the rate of reaction, as particles collide both more often and with more energy
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Presence of a Catalyst
Catalysts are substances that can be used to increase the rate of reaction by reducing the activation energy
A catalyst is neither chemically changed or used up during a reaction, so can be used repeatedly
Catalysts themselves are often expensive, but it is cheaper than paying for the extra energy required for a reaction without them. Reactions with catalysts can take place at lower temperatures and pressures
Catalysts can help reduce the burning of fossil fuels by lowering energy needed, however many catalysts are toxic so should not be released into the environment
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