Assessment and Qualifications Alliance (AQA) GCSE Biology Paper 2 Practice Exam

Collision theory provides a comprehensive explanation for how various factors, such as temperature, concentration, and the presence of catalysts, influence the rates of chemical reactions. According to this theory, for a reaction to occur, the reactant particles must collide with sufficient energy and proper orientation.

An increase in temperature typically raises the kinetic energy of the molecules, leading to more frequent and energetic collisions, which can result in a higher reaction rate. Similarly, when the concentration of reactants is increased, the likelihood of collisions between reactant particles also rises, thereby enhancing the rate of reaction. Catalysts can lower the energy barrier for a reaction, facilitating more effective collisions without being consumed in the process.

Through these principles, collision theory effectively illustrates how and why reaction rates can vary under different conditions, making it the most fitting explanation among the available options.