Chemical Change: Factors that Affect Reaction Rates

Reaction rates refer to how quickly reactants turn into products in a chemical reaction.
Five key factors can affect how quickly a chemical reaction takes place: the concentration of reactants, the pressure of gaseous reactants, the temperature, the surface area of solid reactants and the presence of catalysts.
Concentration: Higher concentrations of reactants lead to more frequent collisions between particles, which can increase the rate of a reaction.
Pressure: In reactions involving gases, increasing the pressure means more particles are packed into a given space. This leads to more frequent collisions and a faster reaction rate.
Temperature: Increasing the temperature increases the energy of the particles, meaning they move faster. This results in more collisions and collisions with more energy, both of which increase the reaction rate.
Surface area: Smaller pieces of a solid reactant have a larger surface area to volume ratio. This provides more area for collisions to occur, leading to a faster reaction rate.
Catalysts: A catalyst lowers the activation energy needed for a reaction to occur. This means that more of the collisions have enough energy to be effective, increasing the reaction rate.
Remember, the rate of a chemical reaction can be measured by the rate of formation of a product or the rate of the consumption of a reactant.
The rates of most reactions increase with temperature, according to the collision theory. The collision theory states that for a reaction to occur, particles must collide with sufficient energy and the correct orientation.
Reversible reactions can reach a state of equilibrium in a closed system. This is when the forward and reverse reactions have the same rate, so the amount of reactants and products remains constant.
Altering conditions, such as pressure or temperature, will shift this equilibrium position either towards the products or reactants. Le Chatelier’s Principle can be used to predict the effects of these changes.
An “Enzyme” is a biological catalyst. They work to speed up chemical reactions in living things. They are not consumed in the overall reaction, and they increase the rate of reaction by lowering the activation energy. Each enzyme works best at a particular pH and temperature, this is known as the optimum condition.