Final answer:
The four liquids do not have the same density despite having the same volume because density is mass per unit volume, and different substances have varying masses for the same volume due to their molecular structures.
Step-by-step explanation:
The four liquids did not have the same density even though they had the same volume because density is defined by the ratio of mass to volume (density = mass/volume). Different substances have different mass for the same volume due to differences in their molecular composition and structure. For instance, water has a density of 1.0 g/mL, which is constant for water regardless of the quantity, but other substances such as corn oil have different densities due to a lower mass to volume ratio, resulting in corn oil floating on water.
Solids and liquids have atoms and molecules that are close together, making their densities higher than gases, where atoms and molecules are separated by empty space. Furthermore, if we consider a block of brass and a block of wood with the same mass, the brass has a greater density and therefore sinks in water, while the wood, having a lower density, floats. Density does not depend on the amount of material but is an intensive property that is characteristic of the substance itself.