Name one phenomenon that can be explained by assuming that matter behaves like a particle.

The particle nature of matter explains various phenomena, particularly at the atomic and subatomic levels, as well as macroscopic observations like Brownian motion.

One phenomenon that can be explained by assuming that matter behaves like a particle is Brownian motion. This is the random movement of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the fast-moving atoms or molecules (particles) in the fluid.

The phenomenon is:
Brownian motion