An understanding of density and specific gravity will make it much easier to "layer" mocktails and cocktails at your next tropical-themed party!
Density: the mass of a substance per unit volume
Specific gravity: weight of a (specified volume of) substance / weight of (an equal volume of) water at the same temperature
Firstly, we need to differentiate between density and specific gravity, so that you can use them to your advantage. It may help you to remember that the density of water is 1g/mL (or 1g/cm3). Similarly, the specific gravity of water is 1.
Try using dimensional analysis to justify why density has units associated with it (?which ones?) and specific gravity does not.
For example, syrups have a greater density than water (~1.3g/mL, depending on the syrup), as do diamonds (3.15–3.53g/cm3)!
In pharmacy, specific gravity and density are most often used when we cannot accurately measure a volume of a liquid (and hence weighing the liquid is more accurate). In these situations, we can use the compound’s density (or specific gravity) to convert between equivalent quantities of the compound in millilitres and grams.
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