Can someone please explain what the 'specific gravity of water' question means? I didn't even know what it was asking for? I have Googled it and can't find an explanation?
Relative density. For liquids, water, at 4 degrees C (when it is densest), is the reference, so water at 4 degrees C has a relative density or specific gravity of 1. At any other temperature it will be less than 1 because it is less dense.
Should specify the units for the specific gravity of water. It has a different value in imperial units (or even if you use different base metric units)
https://oceanservice.noaa.gov/facts/flotsam-jetsam.html
Technically there are zero popes per square kilometer in the Vatican now