Final answer:
The particles in a gas never slow down and stop completely because they are constantly in motion and colliding with each other and the container walls. Solid and liquid particles have forces between them that restrict their movement compared to gas particles.
Step-by-step explanation:
The particles in a gas never slow down and stop completely. This is because gases are made up of tiny particles of matter that are in constant motion, with a lot of distance between them. The kinetic theory of gases describes gas particles as being in constant motion and constantly colliding with each other and the walls of a container. These collisions are elastic, meaning there is no net loss of energy.
For example, if you have a balloon filled with gas and release it, the gas particles inside the balloon will continue to move around and collide with each other and the walls of the balloon until they escape.
In contrast, the particles in a solid or liquid have forces between them that allow them to vibrate or move around, but they do not have the same freedom of movement as gas particles.