Buoyancy is the tendency of an object to float in a fluid if the object is less dense than the fluid. The phenomenon was first discovered by Archimedes and is explained by the upward force a fluid exerts on an object immersed in said fluid.
When attempting to determine the buoyancy of an object in water, it is helpful to know the specific gravity of the object. Specific gravity, also known as relative density, can be determined by dividing the density of a compound by the density of water. The density of water can change with temperature but does not stray too far from 1 gram per cubic centimeter, which makes calculating specific gravity fairly easy. If the specific gravity of an object is greater than 1, it sinks, but if the specific gravity of the object is less than 1, it floats and exhibits buoyancy.
The density of any gas, liquid or solid can be found by taking the mass of the compound and dividing it by its present volume. There are several known densities of common substances, which allows scientists to determine the unknown mass or volume of certain compounds, such as water, as long as the other value, either the mass or the volume, is known.