International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How does increasing the temperature affect the rate of a reaction?

1. The rate decreases

2. The rate increases

3. The rate remains the same

4. The rate fluctuates

The correct answer is: The rate increases

Increasing the temperature generally leads to an increase in the rate of a chemical reaction. This can be understood through the kinetic theory of matter, which states that as temperature rises, the kinetic energy of the molecules involved in the reaction also increases. When molecules move faster, they collide more frequently and with greater energy. These more frequent and energetic collisions are crucial because they increase the likelihood that the particles will overcome the activation energy barrier — the minimum energy required for a reaction to occur. This results in a higher number of successful collisions per unit of time, thus accelerating the reaction rate. In contrast, lowering the temperature would typically result in decreased rates of reaction, while a constant temperature would keep the rate unchanged. Fluctuations in the rate due to temperature would not represent a predictable or consistent outcome, as the relationship between temperature and reaction rate is generally direct and proportional.