Density is a measure of how much mass a material has in a specific volume of space. The more squashed together an object’s particles are, the denser it is. Temperature and pressure are two factors that can affect an object’s density.
Almost all materials become less dense as they get hotter due to their particles moving around more taking up more space. Likewise, when materials cool down they tend to become denser.
Almost all materials will reach their maximum density at very low temperatures and very high pressures. Unusually, one of the densest substances we know of exists only at very high temperatures.
This is called quark-gluon plasma (QGP) and has been synthesised at the Large Hadron Collider by smashing particles of ionised gold together at extremely high energies.
Temperatures 100,000 times hotter than inside the Sun force the atoms to break into their constituent parts – quarks and gluons – and it’s speculated that the universe was made entirely of QGP very briefly after the Big Bang.
Black holes are the densest known objects in the cosmos and are thought to be infinitely dense; considering infinity means ‘no end’, to answer the question, maybe there are no limits to density!
Answered by Rik Sargent