What is density? Density is how much mass (g) an object has in ratio to the amount of volume(unit cubed) said object has. All objects have density, but some object are more dense than others if the atoms that make up the object are packed together are more tightly packed together than the atoms in another object. Why do some objects float while others sink? Objects that float have a density of less than 1g/ml. Objects that have a density of more than 1g/ml will not float and thus sink in water. If