How do you convert 540 ml to grams?

Answer 1

This question cannot be answered sensibly. A millilitre (ml) is a measure of volume, with dimensions [L3]. A gram is a measure of mass, with dimensions [M]. Basic dimensional analysis teaches that you cannot convert between measures with different dimensions such as these without additional information. It takes only a little mental effort to compare a millilitre of air and a ml of lead and come to the conclusion that the two will have very different masses.