The substance's state (solid / liquid / gas), density, temperature, etc, is determined by motion and spacing of particles.
Arrangement of particles determind the phase
P-particles (All matter is made up of particles)I-identical (All particles in one substance are identical)S-spacing (There is different spacing between particles of different substances)A-attraction (Particles have a certain attraction to one another depending on the state)M-movement (Particles are in constant motion)
The motion of molecules in a solid will be extremely slow. The spacing is very close to one another.THe opposite is true of gas. The molecules are extremely fast and they are spaced far apart.
The particle spacing in evaporation refers to the distance between individual particles of a liquid as it transitions to a gaseous state. As the liquid evaporates, the spacing between particles increases, leading to the conversion of the liquid into vapor.
The particles are tightly packed so they vibrate.
Particle spacing is the closest together in solids. In liquids the spacing is close, however the particles have the freedom of movement. In gas, the particles have lots of kinetic energy, therefore they are far apart.
Brownian motion
Brownian motion is the random moving and mixing of particles.
In a gas, particles move randomly due to collisions with other particles and the container walls. The spacing between gas particles is relatively large compared to the size of the particles themselves. This randomness and spacing contribute to the properties of gases, such as their ability to expand to fill a container.
Particles within are limited to vibrational motion, unlike the particles which make up liquids which can have vibrational & translational motion, and gaseous particles which have vibrational, translational and rotational motion.
Unless the particles collide
Brownian motion. This is random motion of micro particles resultimg from collisions between the particle in question and other particles in the surrounding medium.