Liquid: The two key points of a liquid is that the molecules/atoms are slightly farther apart and move slightly faster than a solid, meaning that a liquid's particles can flow past each other, and downwards like all things, due to gravitational energy. Also, a liquid has a fixed mass and a fixed volume, but takes the shape of the container that it is in. Below is an image of liquid and gaseous bromine.
Gas: As the "highest" state of matter that has yet been
discovered, the gas molecules/atoms vibrations are similar to a class-room full
of kindergarteners full of caffeine and chocolate. In other words, the gas
particles are far apart and move past each other rather quickly - faster
than a liquid or a solid. Above is an image of liquid and gaseous bromine.