What property of gases allow them to completely fill whatever space they are in?
The property of gases that allows them to completely fill whatever space they are in is called "diffusion." Diffusion is the process by which particles move from an area of higher concentration to an area of lower concentration. In the case of gases, the particles are constantly in motion and collide with each other, causing them to spread out and fill any available space.
To understand why gases exhibit this property, it is helpful to consider the behavior of gas particles at a microscopic level. Gas particles have high kinetic energy, meaning they are constantly moving in random directions and at high speeds. As they move, they collide with each other and with the walls of their container. These collisions result in a redistribution of the particles throughout the available space.
Additionally, the individual gas particles have negligible volume compared to the space between them. This means that the particles themselves take up very little physical space, allowing them to spread out and fill the entire container.
To summarize, the high kinetic energy and constant motion of gas particles, along with their small individual volumes, enable gases to completely fill whatever space they are in through the process of diffusion.