Comparing the blank of an object with that of a liquid will tell you where or not the objects will float in that liquid

Density

Explanation: Recall Archimedes Principle. There are two forces acting an object submerged in a liquid: the force of gravity and the  (opposite directed) force of buoyancy. The buoyancy is proportional to the mass of the liquid displaced by the submerged part of the object.

Density is the ratio of mass to volume. Therefore if the density of the submerged object is higher than that of the displaced liquid, the net force will point in the direction of the gravity (object will sink). In the opposite case, the net force will point in the direction of the buoyant force (upward) and the object will float.  

increase masses, decrease separation