In DS9's "The Adversary," Odo kills the Ambassador Krajensky Changeling by slamming it into the Defiant's warp core. Injured, the changeling whispers final words to Odo and then crumbles into black ash, dead.
Do all changelings die in this manner? Or was this death and subsequent ashy residue specific to a changeling death caused by a great energy surge?
The changelings that die in both "The Adversary" (s3e26) and "The Ship" (s5e2) turn to a powdery ash when they died. Kilana takes a portion of the founder's remains from the ash pile to return to the Link. We see Odo and the Female Changeling having bits flake off and crumble when they are ill with the Changeling Plague. Also, the infant changeling that merged with Odo was more "lumpy" when poured from the jar than before in the episode. So we can assume the powdering or solidifying of a changeling is synonymous with death.
If so it could be a reason the Changeling feel that making Odo solid is a fate worth than death. In death the powdered remains can be returned to the link and presumably a fraction of the dead can be brought into the link. But if they make him a solid his remains can never return to the link as he would just become dead meat, unable to change form and unable to rejoin the link even in death.
Crumbling into black ash seems to be a common signifier of changeling death as @Tyson of the Northwest shows, though it is not the only way for them to die: in the mirror universe, Odo is hit by a phaser set to kill and promptly explodes, as seen below.
Whether this difference is because of the different manner of death (though phaser and warp core are both energy surges) is not explained. For a liquid-based species, however, it makes sense that their death would be marked by a dessication/drying out process that would leave only ashes behind.
