How do solids, liquids, and gases differ? in solid matter, atoms or molecules pack close to each other in fixed locations; in gases, atoms or molecules pack about as closely as they do in solid matter, but they are free to move; in liquid matter, atoms or molecules have a lot of space between them and are free to move a solid has a fixed volume and rigid shape; liquids assume the shape of their container; gases always assume the shape and volume of their container in solid matter, atoms or molecules pack close to each other but, they are free to move; in liquid matter, atoms or molecules pack about as closely as they do in solid matter, they are also free to move; in gaseous matter, atoms or molecules have a lot of space between them and are free to move relative to one another a solid has a fixed volume and rigid shape; gases assume the shape of their container; liquids always assume the shape and volume of their container