Question

a gas fills the containing vessel fully why?​

Answer 1

Because of the large intermolecular force.......!!

Answer 2

$\bold{Answer!}$

$\large \rm \: Gas \: has \: less \: intermolecular \: force \\ \large \rm \: of \: attraction \: due \: to \: which \: \\ \large \rm \: the \: particles \: occupies \: the \: \\ \large \rm \: whole \: container.$