The process that shows that matter is composed of tiny particles is "crystallization."
Crystallization is the process by which a solid forms from a solution, melt, or vapor and arranges its constituent particles in a highly ordered, repeating pattern called a crystal lattice. When a substance undergoes crystallization, the individual particles, such as atoms, molecules, or ions, come together in a structured manner to form the crystal. This process provides evidence that matter is made up of discrete, microscopic particles.
Expansion, freezing, and melting, on the other hand, are physical processes related to changes in the state of matter:
Expansion refers to an increase in the volume or size of a substance in response to an increase in temperature or other external conditions. It does not directly reveal the composition of matter at the particle level.
Freezing is the process in which a liquid transforms into a solid state due to a decrease in temperature. It demonstrates the transition from a disordered arrangement of particles in a liquid to a more ordered, fixed arrangement in a solid. However, freezing alone does not provide explicit evidence of the microscopic nature of matter.
Melting, conversely, is the process in which a solid substance changes into a liquid state upon the addition of heat. While melting does not directly show the particulate nature of matter, it does illustrate the ability of particles within a solid to move more freely and transition into a less ordered state as a liquid.
Overall, while crystallization is the specific process that highlights the arrangement of particles in a highly ordered crystal lattice, expansion, freezing, and melting are transformations of matter that do not directly reveal the presence or nature of tiny particles.