Which of the following liquids has the lowest density?

Mercury has the lowest density among the listed liquids; option [D]. Mercury’s density is approximately 13.6 grams per cubic centimeter (g/cm³), making it much denser than the other options. Clean water typically has a density around 1 g/cm³, while salty water, which contains dissolved salts, may have a slightly higher density due to the added solutes. Petrol, a liquid hydrocarbon mixture used as fuel, has a density generally lower than water but higher than mercury. However, even petrol’s density is significantly higher than that of mercury. Mercury’s low density is attributed to its atomic structure, consisting of relatively large and heavy atoms closely packed together. This density difference is why mercury sinks when mixed with water, as water has a lower density. Therefore, when comparing the densities of clean water, salty water, petrol, and mercury, mercury has the lowest density, making it unique among the options provided. Thus, the correct option is [D] Mercury.