How do you measure the density of an irregular object that doesnt float?

Answer 1

Ah, the Eureka question. The original questioner in recorded history was of a Greek king whose crown was supposedly made of pure gold. At least the king had given the jeweler a given weight of pure gold and the new crown weighed exactly that amount when it came back. But, the king became suspicious and wanted to be sure his crown was pure gold and the jeweler had not substituted a baser metal for part of the gold.

The king sent for Archimedes who had solved many of the kings problems and asked Archimedes to devise a test for making sure the crown was pure gold. Archimedes thought long and hard over the problem. As the legend goes (and it almost certainly didn't happen this way as Archimedes never wrote about it and the first recording of the legend was about 200 years after Archimedes died), when Archimedes lowered himself into the public baths in Syracuse, the displacement of water from his body caused the bath to overflow, thus giving him the insight in how to measure the volume of an irregular shaped object. Archimedes, according to the legend, then went running naked through the streets of Syracuse yelling "Eureka" which translated means "I have found it."

So, to get to your answer, the density of an object is by definition the mass divided by the volume. First obtain the mass of the object, usually by weighing it. Now determine the volume by immersing your object into a full container of water and either measuring the amount of water that overflows out of the container, or preferably (at least to my mind) measuring how much water it takes to refill the container. Divide the mass by the volume and you have the density.