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Is Dissolving Salt in Water a Chemical Change or a Physical Change?
- WantonQuantum 4y agoI love questions like this because it forces you to examine your assumptions. My first reaction was "Of course it's a chemical change!". But after reading the article I'm putting it in the "it's not clear cut" basket or maybe the "it's both" basket.
- simonblack 4y agoBut then, my first reaction would be that there has been no change but mere dissociation leading to a wider distribution of the sodium and chloride ions throughout the water molecules, and therefore it is only a 'physical change'. The less water you use, the closer the sodium and chloride ions get. Until at the end, the sodium and chloride ions have no water molecules at all separating them as they sit neatly in their crystal lattice. <grin>
- ggm 4y agoThe distinctions between the sciences are moot, and the lower down the organ -> molecule -> atom -> subatomic stack you go, the less clear the distinctions are. Really, I think we should have kept the entire school of science as Natural Philosophy and required some generalist study under the umbrella and a specialisation. All chemical changes are in some sense, physical. The question is, has something happened between molecules, between atoms, or within atoms and between sub-atomic particles. Ions are dissociated but balance in the fluid suspension demands the ratio of Na and CL to H and O remains roughly constant (roughly) -if you reduce the water, then the solution tends to come out of solution because it's no longer isotonic. If you remove some CL and leave surplus NA, it begs questions to what happens next. If you remove surplus H and try to leave the O alone, likewise. Things happen, to keep balance. Balance means respecting the laws of physics. James Doohan was right there. Not a chemist, a biologist or a physicist, this is what my father (a numerical analyst) said to me 4 decades ago.