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dgt20

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Hey can someone explain in a 2-3 sentences for each factor, how each rate of reaction factors (temperature, pressure, concentration, catalyst, surface area) increases speed of reaction.
 

jazz519

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Explain the importance of collisions between reacting particles as a criterion for determining reaction rates (from yr 11 syllabus my notes)
For a reaction to occur, the reactant particles (atoms, molecules, ions) must react with sufficient energy to overcome activation energy barrier. Anything that increases the rate of these particle collisions will increase the rate of reaction.

Nature of reactants - Each reaction has its own activation energy.

Concentration - An increase in reactant concentration means that there is an increase in the number of reactant particles per unit volume. This will lead to an increased chance of collisions, leading to an increase in the number of collisions per unit time. (This relates to pressure because it essentially increases the concentration of the reactants because they are brought closer together in a smaller volume)

Surface Area - If the surface area of a reactant is increased, more of the reactant molecules are exposed to collision. Since particles must collide to react, this will lead to an increased rate of reaction.

Temperature - Increasing temperature speeds up the rate of reaction by providing kinetic energy through the conversion of thermal (heat) energy to kinetic energy increases to reactants and products, allowing more molecules to possess the correct collisional orientation and energy to overcome the EA (activation energy barrier) (therefore there is more successful collisions).

Catalyst: A catalyst is a substance that increases the rate of reaction without being consumed. Catalysed reactions have lower activation energy, than similar uncatalysed reactions. Catalysts work by allowing for an alternative mechanism for the reaction. Effectively this means that more colliding particles will have the required amount of energy for the reaction to occur. The enthalpy of the reaction remains the same. There are two types of catalysts: homogeneous and heterogeneous. Enzyme is a substance produced by a living organism which acts as a catalyst to bring about a specific biochemical reaction.

Breaking big lumps of solid into smaller pieces: This increases the surface area of the solid and consequently, the rate of collision increases as more particles of the solid are exposed to the other reactants, increasing the rate of reaction.
 
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