An illustration of a 500 ml beaker with liquid filled up to 300 ml. why are the marked lines on a beaker like this useful for measuring the volume of a liquid? a liquid maintains its shape in the beaker, so the beaker can measure the liquid’s height, and the height cubed equals the liquid’s volume. a liquid conforms to the circular area of the beaker, and this area multiplied by the liquid’s height equals its volume. a liquid is usually made of neutral atoms, and the beaker does not add or remove energy from the atoms, thereby preventing ionization. a liquid is compressible, but since the beaker does not have a top on it, the liquid will maintain its same volume.