Talk:Boiling point/Draft

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Wikipedia has article with same title

I was one of the major contributors to the WP article. However, I have completely revised and reformatted the article in my sandbox before I created this CZ version. - Milton Beychok 23:11, 9 June 2008 (CDT)

Really ready for approval

Just one thing occurred to me, and it may not be worth mentioning.

Should any reference be made to sublimation/sublimation point? It's related, but not strictly part of an article dealing with liquids boiling. IIRC, some substances that sublime under standard pressure will boil under higher pressure.

It's your call if that's too minor a point; I'm otherwise ready to recommend approval. I hadn't realized you had so many articles at that point.

Howard C. Berkowitz 20:40, 26 December 2008 (UTC)

Hi, Howard: If you will look at the Vapor pressure article I created some time ago, you will see that the sublimation point is defined and discussed in the section entitled "Vapor pressure of solids". I really don't think that discussion needs to be repeated in this article. However, a Sublimation point that redirects to the Vapor pressure article should help readers navigate to where sublimation points are discussed ... so I will create that redirect in the next few minutes. Happy New Year! Milton Beychok 21:06, 26 December 2008 (UTC)

Howard, as for how many articles I've written, just checkout my user page. Milton Beychok 21:06, 26 December 2008 (UTC)

LOL...occasionally, I have put a list on my userpage, but don't keep it updated. How's that for going from the sublimation to the ridiculous? I'll go ahead with the approval on BP.Howard C. Berkowitz 22:30, 26 December 2008 (UTC)

Approved Version 1.0

Congratulations, there falling like cards! This is the version approved. D. Matt Innis 00:18, 4 January 2009 (UTC)

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Approval Notice

Hi all, I am here to perform the approval tasks and noticed that Joe has added a copyedit that might be perceived as a content edit, depending how it is read. I am actually only able to approve to the date that Howard placed on the template which is December 27, 2008 anyway, but if you would like me to include that change,let me know and I can do it later. Meanwhile I will approve without that change. D. Matt Innis 00:09, 4 January 2009 (UTC)

It's truly a copy edit. Go ahead and approve.

Fillet of a fenny snake,
In the cauldron at BOILING POINT and bake;
Eye of newt, and toe of frog,
Wool of bat, and tongue of dog,
Adder's fork, and blind-worm's sting,
Lizard's leg, and owlet's wing,—
For a charm of powerful trouble,
Like a hell-broth boil and bubble.
ALL.  Double, double toil and trouble;
Fire burn, and caldron bubble. 

Howard C. Berkowitz 00:27, 4 January 2009 (UTC)

Just a couple of very minor grammar edits. I can add them into the Draft article after you finish the approval. I agree with Howard ... go ahead and approve. Milton Beychok 00:46, 4 January 2009 (UTC)

Okay, will do. I just couldn't make that decision because they could potentially changed the meaning and needed your okay. Howard is cooking up something sinister for sure ;-) D. Matt Innis 00:58, 4 January 2009 (UTC)

Approval Process: Review period

Call for review: Milton Beychok 21:09, 10 December 2011 (UTC)

Call for Approval: Peter Schmitt 01:04, 22 December 2011 (UTC)

Approval Notice:

Certification of Approval:

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Please discuss the article below, Boiling point/Approval is for brief official referee's only!

Comments

I think the lede has it backwards. It defines boiling point in terms of vapour pressure, then says it may also be defined as the temperature at which the phase change happens. No. It is by definition the temperature at which the liquid boils. Several more precise definitions are possible, either in terms of phase change or vapour pressure.

There's a general principle here, Progressing from simple to complex is better style and makes for easier reading. Sandy Harris 01:28, 22 December 2011 (UTC)

Sandy, your statement "It is by definition the temperature at which the liquid boils" leads one to believe that a liquid has one single boiling point. However, there is no single temperature at which a liquid boils. There are an infinite number of boiling points since the boiling point changes with the surrounding environmental pressure. That is why it is more accurate to define the boiling point in terms of the liquid's vapor pressure being equal to the surrounding environmental pressure.

The only single boiling point of note is the "normal boiling point" which is the special case at which the boiling point occurs when the liquid's vapor pressure equals a surrounding environmental pressure of 1 atmosphere (101.325 kilopascals). That is the boiling point that most lay people think of as being "the" boiling point ... but that is not correct, since a liquid has an infinite number of boiling points. Milton Beychok 18:24, 22 December 2011 (UTC)

I see. But this leads to another suggestion: Your explanation why the "naive" definition is not good enough should be added to the article. (I could try, but it is probably better that you do it?) --Peter Schmitt 22:36, 22 December 2011 (UTC)

Good idea, Peter. I have now expanded the lede to include the discussion of infinite boiling points as you suggested. Milton Beychok 23:54, 22 December 2011 (UTC)

With regard to Sandy's comment I have mentioned the non-scientific definition of boiling point. Is this ok, Milt? --Peter Schmitt 11:57, 30 December 2011 (UTC)

Peter, I don't find your edit objectional even though I don't think it was needed, so I left it as you edited it.Milton Beychok 17:06, 30 December 2011 (UTC)

You are certainly right that it is not needed (from a logical or scientific view). The idea is to help readers who might otherwise be confused. --Peter Schmitt 17:45, 30 December 2011 (UTC)

Reference 1 needs updating. (This shows the limited value of references to web resources -- they are quite volatile.) --Peter Schmitt 11:40, 30 December 2011 (UTC)

Peter, I replaced that inactive hyperlink reference to a website with a book reference. Also added another book reference for good measure. Milton Beychok 17:06, 30 December 2011 (UTC)

1. In the explanations, ln should be roman as in the formula. I don't know how to change this.
2. Preferably, vap should be roman too.
3. The notation for inverse units is inconsistent.

Peter Jackson 10:50, 31 December 2011 (UTC)

1. You are correct and, in the listed parameters of the equation, I changed "ln" to Roman font.
2. I disagree with you on this. I believe that all of the listed parameters should look the same as in the equation itself.
3. I revised the notation of the units for the heat of vaporization to be consistent with those of the molar gas constant.

Thanks for your comments, Peter Jackson. Milton Beychok 16:58, 31 December 2011 (UTC)

Perhaps I misunderstood your item 2 and you meant changing "vap" to Roman font in the equation as well as in the listed parameters. On that basis, I agree and have made that change. Thanks again. Milton Beychok 18:34, 31 December 2011 (UTC)

Yes, that was what I meant. Peter Jackson 11:21, 3 January 2012 (UTC)

.......I copied comment and response from Milton Beychok's Talk page to here at his request on my Talk page.

Milt, since you're one of the main writers of the Boiling point/Draft page, I must say that I expanded this page by adding two more sections, before it went through re-approval. I still would like to expand it a little further, including mentioning azeotropes and adding a new section on experimental "Boiling point determination" in a lab setting, which I have yet to write or even research. Henry A. Padleckas 00:23, 4 February 2012 (UTC)

Thanks, Henry. I agree that a section on "Boiling point determination" in a laboratory setting would be useful. However, I think that azeotropes deserve a separate, stand-alone article. Milton Beychok 15:45, 4 February 2012 (UTC)

Trying to understand 'boiling point' from a undergraduate student perspective--To Milton

Milton, does the following, serving only as an introductory paragraph, correctly and coherently represent the facts? I want to be sure I understand 'boiling point'.

As the temperature of a liquid increases with the application of heat to it, the pressure of the vapor escaping from the liquid and exerting back on and throughout the liquid increases. When the temperature has increased to a point at which bubbles of vapor (gas) begin to form within the bulk of the liquid, that temperature is referred to as the liquid’s boiling point. At temperatures below the boiling point, the total external pressure exerted on the liquid exceeds that portion of it contributed by the pressure of the liquid’s vapor, thereby constraining vaporization within the liquid's bulk. When the rising temperature increases the vapor pressure to equal the total external pressure exerted on the liquid—a pressure transmitted through the bulk of the liquid— the liquid within its bulk is no longer constrained from vaporizing by pressure and then can begin to vaporize within its bulk, and bubbles of vapor can then begin to form.

Anthony.Sebastian 18:55, 15 February 2012 (UTC)

Tony, I'm pleased that you are now our active Approval Manager. First, as an example, please look at the plot of liquid diethyl ether's vapor pressure versus temperature on the vapor pressure chart included in this article. Every point on that graphed line is a boiling point. Since the line has an infinite number of points, then the liquid has an infinite number of boiling points. It is most important that students (undergrad or otherwise) understand that there is no singular boiling point which is "the" boiling point of a liquid. That's why the first sentence of this article's introduction defines a liquid boiling point as "the temperature at which the vapor pressure of the liquid equals the external environmental pressure surrounding the liquid."

Your wording includes this: "... that temperature is referred to as the liquid’s boiling point." That wording might lead students to believe that a liquid has only a singular boiling point referred to as "the liquid's boiling point", which would be incorrect.

Also, other than in a laboratory or a kitchen, boiling very often occurs in an enclosed, non-transparent vessel and therefore the bubbles formed during boiling cannot be observed. Discussing bubble formation in the first introductory paragraph would be a mistake in my opinion. That's why most of your proposed wording is discussed in this article's second paragraph, namely: "The boiling point of a liquid may also be defined as the temperature at which it changes state from a liquid to a gas throughout the bulk of the liquid. At that point, bubbles of vapor which form below the surface of the liquid contain vapor at a pressure which matches the external pressure. Therefore, they are not crushed by the surrounding liquid and their buoyancy causes them to rise through to the surface of the liquid and give the familiar appearance of a boiling liquid."

References 1 is an introductory chemistry textbook in its 4th edition. Hence, it must have proven its worth as a textbook for undergrad students. This is a quote from that reference: A boiling point is the temperature at which the vapor pressure of the liquid becomes equal to the external pressure exerted on the liquid."

In summary, I believe that the current wording of this article's introductory paragraphs should remain as is. Regards, Milton Beychok 03:35, 16 February 2012 (UTC)

Thanks, Milton, I do appreciate your clarification. I was writing more for myself than to suggest a new lede. I do understand that a liquid's boiling point differs depending on ambient pressure, as I have tried cooking spaghetti at altitude. My thought, for the undergraduate, was to bring in that qualification next.

What induced me to try writing it for my own understanding was a problem I encountered with the first sentence you wrote: "The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the external environmental pressure surrounding the liquid." For the naive student, the sentence explains one concept, boiling point, in terms of another concept, vapor pressure, that the student might be unfamiliar with, forcing her to quit her quest to understand 'boiling point' until she first turned to learning what is meant by 'vapor pressure'. And I did not feel that knowing 'vapor pressure', from the CZ article, as

Vapor pressure (also known as equilibrium vapor pressure), is the pressure of a vapor in equilibrium with its liquid or solid phase.[1][2] At any given temperature, for a specific substance, there is a pressure at which the gas of that specific substance is in dynamic equilibrium with its liquid or solid forms. This is the vapor pressure of the specific substance at that temperature.

then gave the student a beginning understanding of 'boiling point'. I thought to approach explaining 'boiling point' in a way that obviates the student's need to first come to grips with 'vapor pressure' as a separate concept, rather letting it emerge to the extent needed to understand boiling point. I didn't do a very good job.

Anyway, I appreciate the opportunity to discuss the matter with you. Anthony.Sebastian 05:22, 16 February 2012 (UTC)

Good point, Tony. I also struggled with the fact that a reader might not know what is meant by "vapor pressure". After considerable thought, I came to the conclusion that we are a wiki for the very reason that it enables us to provide links to other articles explaining the underlying concepts. There just is no way to write an article on boiling points that will also explain what is meant by "vapor pressure", what is meant by "temperature", what is meant by "pressure", what is the "difference between a liquid and a gas", etc., etc., etc. However, a wiki does enable us to send the reader to other articles explaining those underlying concepts. Another alternative is to write a textbook of 400 pages or so instead of writing an encyclopedia article.

This same conundrum applies in other fields. For example, how does one write a mathematics article involving some concept in calculus or differential equations without assuming that the reader "understands algebra", knows how to perform "arithmetic functions", etc., etc., etc.? Again, a wiki enables us to direct readers to other articles that will explain those underlying mathematical concepts. Milton Beychok 06:21, 16 February 2012 (UTC)

Of course, you are right about our being a wiki, able to send the student to another page to look up things he doesn't know. Yet, that's a generalization. In this particular case, we can appreciate a big difference between the more basic concepts of 'temperature', 'pressure', 'liquid', and 'gas'—your examples—and the less familiar and more advanced concept of 'vapor pressure'. I do not see a particular problem defining 'boiling point' in terms of those more basic concepts. A student who didn't have a basic understanding of 'temperature', 'pressure', 'liquid', and 'gas' will soon discover that she needs to go back and learn the basics before trying to understand 'boiling point'.

This is just my opinion: We should do whatever it takes to teach the student about 'boiling point' without requiring her to figure it out for herself after finding out what 'vapor pressure' means, a task that will not be very easy, I suspect, considering how 'vapor pressure' is defined (i.e., as equilibrium vapor pressure). It might be a challenge to introduce the concept of 'boiling point' without requiring the student first study up on 'vapor pressure', but think that challenge could be met.

Nevertheless, what you have written is correct, scientifically. No one said science is easy. I'm happy to defer to your judgement in this matter.

Thanks, again, for the opportunity to engage this issue with you. Anthony.Sebastian 05:39, 17 February 2012 (UTC)

(Unindent)Tony, at the risk of over-talking this, let me make another point and a fairly subtle one. The current lede states that the boiling point of a liquid varies with the "surrounding environmental pressure" rather than with the "ambient pressure". That was done deliberately because the "ambient pressure" is often taken to mean the outdoors atmospheric pressure.

A closed storage tank full of liquid propane, for example, is not subject to the outdoor "ambient pressure". The "surrounding environmental pressure" inside that tank is the vapor pressure of propane at the temperature of the stored liquid within the tank. By either cooling or heating the stored liquid, the "surrounding environmental pressure" within the tank is lowered or raised. The point I hope to make with this is that it is unwise to use the words that "the boiling point of a liquid varies with the ambient pressure" ... because that can be misconstrued. Even some of this article's references use that poorly chosen wording of "ambient pressure". That is just one example of why I believe that the primary recourse to be taken in science articles is to be as scientifically correct as possible. Yes, that may make it difficult for some undergrad students or unknowledgeable readers. On the other hand, if the article is not scientifically correct, then it may confuse graduate students or knowledgeable readers. Milton Beychok 06:34, 17 February 2012 (UTC)