Talk:Boiling point

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Half way down the page it states 260mbar is 26.39kPa. This is at odds with the article for Pascals, which states that 1 bar = 100,000 Pascals. — Preceding unsigned comment added by 86.160.105.124 (talk) 18:37, 2 June 2011 (UTC)[reply]

There should be discussion of the phenomenon of boiling point elevation in solutions, that the boiling point of salt or sugar water is higher than the boiling point of pure water, and why. -- Dominus 05:54 Apr 20, 2003 (UTC)

Mm, colligative properties, you mean (also explains why salt lowers the melting point of ice). I'll see what I can do.DS 14:44, 5 Sep 2004 (UTC)

Could we put the fahrenheit boiling point of water also. My 9 year old daughter attempted to find that value and was frustrated by its absence.Ark30inf 07:19, 20 Aug 2003 (UTC)

It's there now. -- Someone else

I added a section at the end that briefly discusses

boiling point elevation, but if you want more detail, go to the separate article on that. H Padleckas (talk) 20:37, 6 March 2012 (UTC)[reply

]

Looking at the definition of boiling and the bit about adding heat not changing the temperature, would a better definition for boiling point be the maximum temperature a a substance can be increased to as a liquid? Martschink 18:04, 24 Jun 2005 (UTC)

You have to talk about the vapor pressure of the liquid and the pressure of the surroundings any time you talk about boiling. If I increase the pressure above a liquid, I will increase the boiling point or if I decrease the pressure, I will decrease the boiling point. Both of these observations result from the changing in the pressure of the surroundings. Boiling occurs when the vapor pressure reaches (incrementally exceeds) the pressure of the surroundings.

I think this article would also be more helpful if it talked about whether or not intermolecular forces or dissolved impurities have anything to do with the boiling point

Dissolved impurities change the boiling point only because they change the vapor pressure of the solution by "diluting" the concentration of the molecules that are producing the vapor pressure. If the dissolved impurity has a higher vapor pressure, it will increase the vapor pressure of the solution and thus lower the boiling point. Dalton's Law of Partial Pressures explains this by saying that the total vapor pressure of a solution is the sum of the partial pressures of each of the components. The partial pressure of a dissolved material (solute if it is a "minority" in the solution) is largely the composite result of the concentration of the solute molecule and the vapor pressure of the solute at the temperature of the solution. If you have something like sugar in water solution (candy making), the sugar has very little vapor pressure. When the temperature of the boiling candy increases, the concentration of water is falling and that of sugar is rising. When you get to the right temperature for the candy, you have really gotten to the desired concentration of water and sugar. The candy thermometer is just a simple way of measuring this concentration. —Preceding unsigned comment added by 70.240.66.35 (talk • contribs) 15 October 2006

There is a discrepancy with the statement of boiling point of water on the top of mount Everest as well as the atmospheric pressure from this article and other wikipedia articles. http://en.wikipedia.org/wiki/Olympus_mons http://en.wikipedia.org/wiki/Mount_Everest vary the atmospheric pressure from 33.7 KPa to 32 KPa for the summit of Mount Everest. http://www.physics.org/facts/air.asp states the boiling point of water on the summit of Mount Everset is 72 deg C, while this article gave a better rational and an equation for boiling water http://wiki.answers.com/Q/How_does_the_elevation_and_air_pressure_affect_the_boiling_point_of_water. I found this table for the boiling point of water http://www.iapws.org/faq1/boil.htm that may be useful for this article. Cheers. — Preceding unsigned comment added by 96.44.105.39 (talk) 13:30, 27 March 2012 (UTC)[reply]

What is the difference between heat and temperature?

I think that heat (as a noun) is shorthand for thermal energy, and temperature is a ratio between thermal energy and volume. For example, if you were to measure an amount of heat, it could be measured in Joules (or any units for energy), whereas temperature would be measured in J/cm^3 or degrees Centigrade, or whatever. MisterSheik 08:05, 10 Mar 2005 (UTC)

Heat is the average Kinetic energy measured in joules. -Kayla

This comment needs to be deleted, as the answers are flat wrong (and apparently have existed for two years!). For the record, temperature is a measure of the statistical distribution of energy states in a system (which can be measured in units of energy (Joules in SI)) while heat is work done to a system by the exchange of energy states through a reservoir, also measured in Joules. Fundamentally, a change in heat means changes both energy and entropy. SamuelRiv 13:52, 5 November 2007 (UTC)[reply]

A lot of different sites give different numbers on the boiling points of various elements, particularly Rhenium and Tungsten. This site gives Re's as 5627 and W's as 5660 Kelvin. Wikipedia currently has Re at 5869 and W at 5828 Kelvin. Chemicalelements.com has Re at 5900.15 °K, W at 5933.15 °K. So who do we believe? There's a disagreement that ranges almost three hundred degrees Kelvin here. Mr. Billion 17:49, 24 Jun 2005 (UTC)

First, discount those with the .15 at the end. They are obvious conversions, implying more precision than they actually have, from 5,627 °C and 5,660 °C respectively. Now, surprise, that's what the other site you cited has for the temperature in kelvins. One of them obviously misidentified the units being used. Dig into it with the idea that the actual numbers may be close to those numbers, on some scale.

Of course, the number 5,627 looks pretty suspicious itself, as a likely conversion to degrees Celsius from 5,900 kelvins, without that .15 at the end. Another case where the conversion was probably carried to too many places, but at least they had enough sense to drop those afer the decimal point. I'd suggest 5,900 K with some significant number of kelvins of uncertainty as the likely best value for rhenium.

In general, look first to see if the numbers are more rounded numbers in some other scale. Gene Nygaard 23:55, 24 Jun 2005 (UTC)

At the Help Desk, HappyCamper says he's confirmed that Wikipedia's numbers are correct and that Rhenium has the higher boiling point. But what you're saying seems to cast doubt on what he's saying is correct. Could be his source is wrong, but... I don't know. Mr. Billion 03:23, 25 Jun 2005 (UTC)

I cut "The element with the highest boiling point is Rhenium.". It didn't make sense to say it if the next line discredits it. If you feel strongly for it, put something like 'wikipedia believes', but it cuts down on confusion to just not have it their in the first place. Capi crimm 06:33, 16 July 2005 (UTC)[reply]

Perhaps some sources are reporting normal bp and other sources are reporting standard bp. The difference in pressure could make that much of a difference in bp. Just a thought. El Zarco 08:20, 27 November 2011 (UTC) — Preceding unsigned comment added by ElZarco (talk • contribs)

The first sentence states:

The boiling point of a substance is the maximum temperature at which a liquid can remain a liquid.

That is incorrect. There is no such thing as "The boiling point". Every liquid has different vapor pressures at different temperatures. Graphs of vapor pressure versus temperature of a liquid are called "vapor pressure curves". Thus, any liquid may have an infinite number of boiling points since such curves have an infinite number of points. The correct definition of a liquid's boiling point is "the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid." Thus, a liquid in a vacuum environment has a lower boiling point than when the liquid is at atmospheric pressure. And a liquid in a high pressure environment has a higher boiling point than when the liquid is at atmospheric pressure. That's how high-pressure steam is made ... by boiling water that is at a high pressure. This is elementary, high school chemistry!

The second paragraph in the article states:

A somewhat clearer (and perhaps more useful) definition of boiling point is "the temperature at which the vapor pressure of the liquid equals the atmospheric pressure."

That is also incorrect. That only defines what is called the "atmospheric boiling point" or the "normal boiling point" ... which is only one of the infinite number of boiling points a liquid may have. The title of this article is "Boiling point" ... it is not "Atmospheric boiling point".

This article was first created in September of 2001, which is over 6 years ago. It is mind-boggling to think that the above definitions were never questioned during all that time. This isn't rocket science or quantum physics, it's simple high school chemistry.

I regret having to be so blunt, but much of this article deserves that bluntness. Wikipedians who don't really understand simple chemistry and physical chemistry should not edit this article. - mbeychok 08:15, 6 October 2007 (UTC)[reply]

I think it's best form to introduce the concepts like "boiling point" while relying on as few other complex concepts like "vapor pressure" and "atmospheric pressure" if it is possible. :For instance.. the original, incorrect quote could be appended to read as follows:

"A boiling point for a substance is the maximum temperature the substance can remain before turning into gas."

Then a follow up sentence --like The boiling point for a liquid is dependant upon the pressure of it's environment and the substance's (insert chem word for "inclination to become gassious")-- could be used to refine and expand upon the first sentence's definition; adding a second tier of complexity to that simple matter of chemistry. —Preceding unsigned comment added by 96.18.60.113 (talk) 07:45, 5 December 2008 (UTC) [reply]

You're responding to a comment posted over a year ago, and the article has changed since then, and I don't see the troublesome wordings in the current article text. On the other hand, the definitions we have now are multiply cited. I think you have some valid concerns about the style and level of the introduction, but the current statements are verifiably correct. Your statement goes too far, dumbing it down (sorry) until it's not even correct (do solid substances have a boiling point? And liquids can become superheated above their boiling point.) rather than just requiring a less technical background to understand. DMacks (talk) 08:18, 5 December 2008 (UTC)[reply]

True about the dates, I posted only for the sake of other readers of the post (I disagreed with his writing philosophy/style as you noted and would promote my own as well), not necisarily in direct discussion with the original poster. When you ask "do solid substances have a boiling point?" I'd say yes because a boiling point is a property of a substance and phase state is another property (substance.phase = gas  ; substance.boiling_point = X if that makes more sense) although maybe the wording could use more thoughtful touch up. You caught me (thx) on the superheated point though, I have to admit, I actually am not too firmilure with that concept at all (beyond "avoid heating things in micros"). There must be a simple clause we could use to create an exception catch for superheated materials, like "A boiling point for a substance is the maximum temperature the substance can reach before it must become gassious *(in a Nucleation-disturbed environment)*." of course Nucleation-disturbed isn't nearly suitible, I just don't know enough about superheated liquids and I should do sleep for a while. You are very true, correctness is more important than understandability, but understandability should be strived for if there are few enough exception clauses required. —Preceding unsigned comment added by 96.18.60.113 (talk) 09:08, 5 December 2008 (UTC)[reply]

Can someone please explain to me the difference between steam point and boiling point?

Or is it the same thing? well what is the boiling point in celsius please —Preceding unsigned comment added by 124.176.44.153 (talk) 05:09, 17 May 2008 (UTC)[reply]

I don't know what you mean by "steam point" ... that is some new terminology to me. If you are talking about the boiling point of water, it is 100 °C at sea level atmospheric pressure. But at any other pressure, it would be different. For example, at the top of a high mountain, the boiling point of water is less than 100 °C.

If you will read this article slowly and carefully, you will see that the boiling point of any liquid depends on the pressure surrounding the liquid. You will also see that this article is about any liquid, not just water. - mbeychok (talk) 22:15, 17 May 2008 (UTC)[reply]

• • • will you go out with me???? —Preceding unsigned comment added by 76.7.0.108 (talk) 14:19, 15 April 2009 (UTC)[reply]

never mind i don't want to anymore

My kid looked up the defintion of boiling point here on Wikipedia and got a headache. This is overly complicated. Give a basic laymen term definition then go into the doctoral-orgasmic Ph.D. bulls**t. —Preceding unsigned comment added by 71.188.231.28 (talk) 23:32, 17 February 2010 (UTC)[reply]

Perhaps the Simple Wikipedia would be a good place to turn when the English one gets too technical? The "Simple English" in the left margin goes to a page that is more in tune with what a lay reader probably wants. It's no excuse for the inaccessible mess here, but it's a good trick in general for readers to know. Feel free to suggest specific improvements...Wikipedia is the encyclopedia anyone, even frustrated readers, can edit. DMacks (talk) 04:07, 18 February 2010 (UTC)[reply]

what is principle of boiling point and melting point? —Preceding unsigned comment added by 115.248.151.2 (talk) 10:46, 28 January 2011 (UTC)[reply]

Hi. Wikipedia is very useful in providing data, such as the boiling point of numerous chemicals. Does anyone know if those are normal boiling points or standard boiling points? For some things, it does make a difference. Thank you! El Zarco 08:22, 27 November 2011 (UTC)

This article is skimpy. A number of factors influence boiling points, such as atomic weight of elements and types of bonding of compounds. It would be nice to have a section discussing these factors. — Preceding unsigned comment added by Skysong263 (talk • contribs) 22:44, 18 December 2011 (UTC)[reply]

You have a point. I have improved a Citizendium article on "Boiling point" by adding two sections there which discuss these factors and other important things. Some day I plan to insert them here also to improve this article. H Padleckas (talk) 19:36, 6 March 2012 (UTC)[reply]

I have just inserted those two sections here along with a picture of a hypothetical example of a binary boiling point diagram. Maybe some day I'll add a sentence or two on azeotropes to the mixtures section at the end. Also, it would be a good idea to have a section on experimental (laboratory) boiling point determination. Does anybody care to write one? H Padleckas (talk) 20:06, 6 March 2012 (UTC)[reply]

Hello,

I was just using the Clausius-Clapeyron equation on this page and I believe you may have missed out a variable in the equation, which you stated as:

T_B = \Bigg(\frac{\,R\,\ln(P_0)}{\Delta H_{vap}}+\frac{1}{T_0}\Bigg)^{-1}

But it is without the relative pressure calculation "(P0/P)" that is requisite. It should therefore be:

T_B = \Bigg(\frac{\,R\,\ln(\frac{P_0}{P})}{\Delta H_{vap}}+\frac{1}{T_0}\Bigg)^{-1}

If I have misunderstood anything and this was intentional for some reason or another, I apologise, I am not an expert on chemistry or thermodynamics.

NiklasZ (talk) 11:29, 26 March 2012 (UTC)[reply]

The logarithm of P₀/P is equal to the logarithm of P₀ when P (the normal atmospheric pressure) is expressed in atmospheres because then P = 1 atmosphere. If P is expressed in any other units (Pa, bar, torr, etc) then the equation should indeed include P ... however, the equation as it currently stands is correct since P is expressed in atmospheres. mbeychok (talk) 17:51, 26 March 2012 (UTC)[reply]

198.177.184.17 (talk) 23:36, 5 February 2015 (UTC) Typo? The variable definition states: "P = is the vapour pressure of the liquid at the pressure of interest . . ." Shouldn't it state that P = the vapor pressure of the liquid at the temperature of interest (temp not pressure)? Vapor pressure is a function of temperature. As stated it does not seem to make sense. Also, the equals sign & the word "is" are redundant - delete the word "is".[reply]

I've added a few parts from this article at

To User:Materialscientist,
I think the addition of the latest graph, which is the image

I've enlarged the above image from 350px to 500px in the article for improved readability and repositioned the pic to a center position instead of the right side. I also made a few edits, mostly minor, to this image in WikiCommons for better visibility. If somebody has any ideas for further editing the image to improve it, they can edit the latest version or any other version of File:Boiling point vs molar mass graph.png in WikiCommons. It's even possible to edit parts of both, then superimpose either one on the other, assuming one knows how to do that. H Padleckas (talk) 23:20, 10 June 2014 (UTC)[reply]

As of 3/5/2015, reference 7 points to a McGraw-Hill textbook appendix instead of the actual IUPAC publication, which can be found here on pages 1246-1247 132.170.57.13 (talk) 19:59, 5 March 2015 (UTC)[reply]

Added ref, thanks. Materialscientist (talk) 21:45, 5 March 2015 (UTC)[reply]

Need a reference for the following quote:

"For example, water boils at 100 °C (212 °F) at sea level, but at 93.4 °C (200.1 °F) at 2,000 metres (6,600 ft) altitude"

But the United States Dept of Agriculture states "With each 500-feet increase in elevation, the boiling point of water is lowered by just under 1 °F" ^[1]

Therefore, at 6600 feet, water boils at 208 F Therefore, at 2km, water boils at 97.8 Celsius

Cleverwater (talk) 14:34, 6 November 2016 (UTC)[reply]

Um.... No. The maths is wrong. 6600 is equivalent to 13 * 500 ft (approx) and on that calculation, the boiling point of water would be 199 degrees Fahrenheit at 6600 ft. I always regard any source that talks in approximations as being intended for a non technical audience (hikers and campers perhaps?) and not usable in this sort of article. Incidentally the source itself says that water boils at 208 Degrees F at 2000 ft and not at 6600 feet. Always pays to read the source. Regards  Velella  ^{Velella Talk}   16:23, 6 November 2016 (UTC)[reply]