OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Which of the following statements is true about particles during diffusion?

1. They move in one specific direction

2. They move randomly and spread out

3. They only move if energy is added

4. They form clusters instead of spreading out

The correct answer is: They move randomly and spread out

During diffusion, particles move randomly and spread out due to their inherent kinetic energy. This random motion allows them to move from areas of higher concentration to areas of lower concentration, resulting in an even distribution over time. The process is driven by the natural tendency of particles to move and collide, leading to the gradual mixing of substances. In contrast, the other statements do not accurately reflect the nature of diffusion. The notion of moving in a specific direction suggests a directed movement towards a particular point, which is not characteristic of diffusion. The idea that particles only move if energy is added implies the involvement of external energy sources, which is not the case as diffusion is a passive process relying solely on the energy already present within the particles. Lastly, the formation of clusters contradicts the principle of diffusion, where the aim is to achieve uniformity rather than clustering.