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When $\ce{NaCl}$ is dissolved into water it breaks down into $\ce{Na+}$ and $\ce{Cl-}$. It stays in this form until the water evaporates and then the ions go back to normal $\ce{NaCl}$. So why does water with salt in it still taste like salt? I am asking because if the molecule $\ce{NaCl}$ is broken down into $\ce{Na+}$ and $\ce{Cl-}$ then how does it have the characteristics of $\ce{NaCl}$?

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    $\begingroup$ One interesting thing to note is that NaCl actually forms an ionic crystal, which means that even in solid form, you're still dealing with ions. The charges balance and stabilize one-another, resulting in the characteristic brittle crystalline structure of table salt. $\endgroup$ – Dan Bryant Oct 3 '14 at 18:25
  • $\begingroup$ Answers below. Just one question. Why are you assuming that Na+ and Cl- should taste differently when they're apart than when they're together? $\endgroup$ – Mr Lister Oct 5 '14 at 7:22
  • $\begingroup$ @MrLister Neither Cl- nor intact crystals can pass through the ion channel in the taste receptors as it is a very narrow, positively-charged path. Even if it were possible for NaCl to remain as a crystal up to the threshold of the taste receptor, it wouldn't be able to enter it. $\endgroup$ – Michael DM Dryden Oct 5 '14 at 17:30
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When you taste salt, you're not pushing crystalline $\ce{NaCl}$ into your taste buds. It dissolves in your saliva and dissociates. When one tastes salt, the saltiness taste receptors respond specifically to the sodium cation. That type of taste receptor is a cation channel. This is why lithium and potassium cations also taste salty (though they also stimulate other receptors which make them taste somewhat different).

There seem to be at least two types of receptors that respond to saltiness. One responds almost specifically to sodium at low concentrations, but at higher concentrations, the other type responds to many cations. See here

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Have you ever tasted salt that was not dissolved in water? Think about this. Have you ever tasted ANYTHING that was not dissolved in, or in contact with, water? The answer is "No", unless you have the worst case of chronic dry mouth ever to exist in the history of humanity, and if you do have that terrible case of dry mouth, you no longer taste anything.

This is because everything you taste is sampled by your taste buds after having samples of its molecules transported through pores on your tongue by water. No water, no taste. And saliva, of course, is mostly water. If you place a dry grain of salt on your tongue, saliva immediately dissolves a bit of it, and transports that salt through taste pores, where receptors in your taste buds report its flavor.

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I'm not a biology expert, so I'm not sure how the $\ce{Na+}$ and $\ce{Cl-}$ ions actually activate certain taste receptors in your tongue such that you can taste the $\ce{Na+}$ and $\ce{Cl-}$ ions.

However, for the chemistry part, do remember that even when you are putting solid $\ce{NaCl}$ into your mouth, the saliva in your mouth will dissolve it, resulting in the breaking of the ionic bond between $\ce{Na}$ and $\ce{Cl}$. Sodium chloride is so soluble that even a tiny drop of water could dissolve a significant amount of salt - probably more than what you would put into your food.

Therefore, it doesn't really matter if you taste solid sodium chloride or sodium chloride solution - they will all taste the same, but perhaps varying in intensity.

Interestingly, if you are able to find a sodium chloride crystal large enough, and ensure that your tongue is dry enough, I believe(again I'm not a biology expert) that you would not be able to taste the sodium chloride, as solid crystals cannot diffuse as easily into your tongue and activate the sodium channels.

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When $\ce{NaCl}$ is dissolved into water it breaks down into $\ce{Na+}$ and $\ce{Cl-}$.

No, not quite. Dissolving something in water does not break the chemical bonds of the molecule*. You still have $\ce{NaCl}$ molecules floating about. That would leave you with elemental sodium and elemental chlorine, and those two fellows are a bit like drunk bikers.

Mixing sodium, chlorine and water will produce all sorts of things like sodium hypochorite ($\ce{NaClO}$, best known as bleach), sodium hydroxide ($\ce{NaOH}$ - caustic soda) and some lesser-known chlorine compounds. Many are rather dangerous, and I don't think we would have survived as a lifeform if a bit of salt on our food turned into bleach (which destroys DNA) after a Perrier chaser.

  • exception: some molecules will react with water rather than simply dissolve in in it. Depends on a number of factors.
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    $\begingroup$ Since when NaCl forms molecules? $\endgroup$ – Matteo Italia Oct 4 '14 at 15:09
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    $\begingroup$ You are actually joking, right? $\endgroup$ – Dawood ibn Kareem Oct 4 '14 at 20:52
  • $\begingroup$ Not saying that this answer isn't wrong, but the OP also said "molecule". david may just have taken the OP's nomenclature and worked with that. $\endgroup$ – Mr Lister Oct 5 '14 at 7:18
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    $\begingroup$ @MrLister True, but we expect those answering the questions to know more than those asking them. David could easily have explained the difference between things that come in crystals and things that come in molecules. I can only assume that he thought it was April Fools' Day. $\endgroup$ – Dawood ibn Kareem Oct 6 '14 at 6:49

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