DENSITY OF SOLIDS
 

The density of a solid is measured in terms of the number of kilograms contained in a cubic meter. That is, density is equal to mass divided by volume. The kilogram per meter cubed (kg/m³ or kg . m^-3) is the measure of density in the International System (SI). It’s a rather awkward unit in most reallife situations. Imagine trying to determine the density of sandstone by taking a cubical chunk of the stuff measuring 1 m on an edge and placing it on a laboratory scale! You’d need a construction crane to lift the boulder, and it would smash the scale.
Because of the impracticality of measuring density directly in standard international units, the centimeter-gram-second (cgs) unit is sometimes used instead. This is the number of grams contained in 1 cubic centimeter (cm³) of the material in question. Technically, it is called the gram per centimeter cubed (g/cm³ or g . cm^-3). To convert from grams per centimeter cubed to kilograms per meter cubed, multiply by 1,000. Conversely, multiply by 0.001.
You certainly can think of solids that are extremely dense, such as lead. Iron is quite dense too. Aluminum is not so dense. Rocks are less dense than most common metals. Glass is about the same density as silicate rock, from which it is made. Wood and most plastics are not very dense.