Talk:Boiling point

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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

1 Definition
2 Heat and temperature
3 Facts on Boiling points of various elements
4 Pic
5 difference between boiling point and steam point

[edit] Definition

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.

[edit] Heat and temperature

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

[edit] Facts on Boiling points of various elements

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)