Measuring Solid Volume:
Assume that the object in question is irregular. How can we identify that its volume is 45.3 cm3? It would be simple to figure out the volume when the object was a perfect sphere or a perfect cube or a rectangular prism. Assume, though, that it is a knobby little thing?
Scientists have come up with an intelligent way of measuring the volumes of irregular solids: submerge them in a liquid. At first, measure the quantity of liquid in a container as shown in figure (a). Then measure the quantity of liquid which is displaced whenever the object is entirely submerged. This will show up as an increase in the apparent quantity of liquid in the container which is as shown in figure (b). One milliliter (1 ml) of water occurs to be accurately equivalent to 1 cm3, and any fine chemist is bound to have some containers marked off in milliliters. This is the way to do it, then, offered the solid does not dissolve in the liquid and which none of the liquid is absorbed into the solid.
Figure: Measuring the volume of a solid. (a) a container with liquid though without the sample; (b) a container with the sample totally submerged in the liquid.