Lets think about entropy. Entropy greatly favors random, crazy, and disordered options for key, simplified ideas to think about. With this in mind which state has the most "crazy" or the most disorder going on? Solids are pretty fixed in place, liquids have a little more freedom, and gasses can go crazy, moving around and causing agreat deal if disorder. Imaging it this way is helpful? =)
You can find the volume of an irregular object by immersing it in water in a beaker or other container with volume markings, and by seeing how much the level goes up.
