So I came across this question asking whether something is physical or chemical.

Table salt is composed of $\ce{Na}$ & $\ce{Cl}$. Is it a physical property or a chemical property?

I really don't understand why the answer says its a chemical property. I asked the others and they did not give me an understandable answer.

Edit: Now as I think about it, I really don't think there is an accurate answer, even if the book said it was chemical. Bad question from the book.

  • $\begingroup$ Why do you think it should be physical? $\endgroup$ – M.A.R. Jan 10 '15 at 18:05
  • $\begingroup$ @MARamezani I think it should be physical because you are looking at what the compound is physically composed of. There is nothing there that tells me that it is chemical. Physical because you are looking at the physical atoms it self. And since there is no evidence of any chemical change or property, I go with physical. Whats your view into this? $\endgroup$ – Asker123 Jan 10 '15 at 18:07
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    $\begingroup$ There is not enough information provided to give an informed response to the question. All I see is a compound being described. It's similar to saying limestone is made from seashells. It doesn't indicate any properties. If I said how the seashells are transformed, that would be a chemical property. It is not a description of a physical property (as the temperature, or a solid). It is not a description of a chemical property (as in how reactive it is, or a chemical reaction). $\endgroup$ – LDC3 Jan 10 '15 at 18:36
  • $\begingroup$ @LDC3, Yes I think that is true. I have also arrived at that conclusion, but I do not know why such a question would be asked. $\endgroup$ – Asker123 Jan 10 '15 at 18:45
  • $\begingroup$ I do have painful experiences of these crazy-driving questions. GGGoooosssshhhhh! $\endgroup$ – M.A.R. Jan 10 '15 at 19:19

The problem rises when we are mistaken about what a property is.

The different types of matter can be distinguished through two components: composition and properties. UCDavis

Do a search about chemical property, and you get:

a property or characteristic of a substance that is observed during a reaction in which the chemical composition or identity of the substance is changed. Dictionary.com

A chemical property is any of a materials properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity. Simply speaking, chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected for its chemical properties to be investigated. However a catalytic property would also be a chemical property. Wikipedia

Any characteristic that can be determined only by changing a substance's molecular structure. Boundless

What's a physical property?

A physical property is any property that is measurable whose value describes a state of a physical system. The changes in the physical properties of a system can be used to describe its transformations or evolutions between its momentary states. Physical properties are often referred to as observables. They are not modal properties. - Physical property in wikipedia.

Basically, a physical property is what that doesn't deal with the composition of matter; but other factors, such as it's physical state. "Physical" isn't at its literal meaning.

Table salt is never pure $\ce{NaCl}$; because simply there's nothing pure in the nature. It's mainly composed of Sodium Chloride crystals. But if, and only if, we consider it to be only made from $\ce{NaCl}$, we are talking about its chemical composition and therefore, it must be a chemical property.

I understand that sometimes there are wrong questions for us to answer, so if composition is to be a property, it must be a chemical one.

  • $\begingroup$ But everywhere online I've seen it saying, a chemical property is visible in only a reaction. Why is this? $\endgroup$ – Asker123 Jan 10 '15 at 18:26
  • $\begingroup$ According to UCDavis, talk about matter has two "components". First is composition, the other is its properties. Composition is supposedly very different from properties. And yes, chemical properties are only visible in chemical reactions, and that's because they change. $\endgroup$ – M.A.R. Jan 10 '15 at 18:34

First, table salt is composed of $\ce {NaCl}$ wich is different from $\ce {Na}$ & $\ce{Cl}$.

Second, actually table salt isn't exclusively composed of $\ce {NaCl}$ depending of the soure but contains also a fair amount of $\ce {KCl}$

Third, composition isn't what you can call a "property". I mean, it's a definition, compound containing only $\ce {NaCl}$ or other $\ce {KCl}$ is table salt that's all.

  • $\begingroup$ Yes but that's not an option for a question. Why does it take it as a chemical property since you are saying it as 'composition'? $\endgroup$ – Asker123 Jan 10 '15 at 18:15
  • $\begingroup$ Composition isn't a "property". $\endgroup$ – Babounet Jan 10 '15 at 18:31
  • $\begingroup$ @AwesomeFlame123 Yes, your problem stems from that the composition isn't a property - so it's neither physical nor chemical... $\endgroup$ – Mithoron Jan 10 '15 at 23:53

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