What is Boiling point: Definition and 127 Discussions

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.
The boiling point of a liquid varies depending upon the surrounding environmental pressure. A liquid in a partial vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a higher boiling point than when that liquid is at atmospheric pressure. For example, water boils at 100 °C (212 °F) at sea level, but at 93.4 °C (200.1 °F) at 1,905 metres (6,250 ft) altitude. For a given pressure, different liquids will boil at different temperatures.
The normal boiling point (also called the atmospheric boiling point or the atmospheric pressure boiling point) of a liquid is the special case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level, one atmosphere. At that temperature, the vapor pressure of the liquid becomes sufficient to overcome atmospheric pressure and allow bubbles of vapor to form inside the bulk of the liquid. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of one bar.The heat of vaporization is the energy required to transform a given quantity (a mol, kg, pound, etc.) of a substance from a liquid into a gas at a given pressure (often atmospheric pressure).
Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation. Evaporation is a surface phenomenon in which molecules located near the liquid's edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, resulting in the formation of vapor bubbles within the liquid.

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  1. SCHROEDERFPM

    I H2O/gold solution will not boil

    This is my solution and it remained still and did not bubble once while the pot boiled . I realise salt and oil impurities may increase the boiling point but I wouldn't imagine to this extent, and when I filtered the solution the oil seemed to collect the copper and other dissolved metals...
  2. C

    Do you need to account for the water heating up to the boiling point?

    High School Physics Lab: Take 200mL of water (Room temp) and place it in a microwave on high for 60 seconds. Calculate the Energy transferred to the water by the microwave. Pretty easy: Step 1: Heat of Temp Change : Q= mC∆T where m=200mL Step 2: Add Heat due to phase change: Q=mL where m=...
  3. chemisthypnos

    Searching for Low Impact Fluid with Boiling Point of 150-180 F

    I am looking for a good working fluid whose boiling point is in the range of 150-180 F for a waste heat recovery system. The fluid should be minimally flammable, preferably nontoxic, and low in environmental impact. Does anyone know of any working fluids that match this description?
  4. yecko

    Vaporization latent heat vs boiling point

    answer is 78oCdelta G = delta H - T delta S -235,310- (-277,690) = -38.56e3- T (282.59-160.70) T = -664K I am not sure if my concept is correct. May anyone help a little bit on that please? thank you
  5. docnet

    Boiling point of a solution

    The professor posted a take-home problem for us to solve for extra credit. Extra credit problem: Using nothing but pen, paper and a ham, calculate the boiling point of 1:1:1 solution of benzene, pentane, and ethylene in a pressurized tank filled with neon at 6 atm pressure. The Answer must be...
  6. il postino

    Chemistry Calculate the boiling temperature of methanol from thermodynamic data

    Calculate the boiling temperature of methanol at 60 atm knowing that Tc = 513K, Pc = 78 atm and the acentricity is 0.555. I would like you to help me start the exercise. I thought about using the Pitzer Correlation to be able to calculate the fugacity coefficient, but I don't have the...
  7. T

    Is cavitation worse at depth? (Fluid pressure and Vapor pressure boiling)

    I am wondering about the impact of the hydro static pressure of a fluid on its boiling point. The simplest real world example scenario I can think of is the rate/onset of cavitation at a large depth vs a shallow depth. As we increase the submarine propellor speed to a speed where the adjacent...
  8. J

    Adding xylitol to hot water lowers the boiling point and makes it boil

    This probably occurs with salt too but let's concentrate on xylitol: you heat water till it boils, put the hot water in a cup and add a tsp of xylitol. It boils again violently for a couple of seconds. The high school explanation is that the boiling point of the water is lowered. I'd like to...
  9. José Ricardo

    Boiling point and connection distance of the elements

    Homework Statement Explain the following order of the boiling point (° C) HF (19.5)> HCl (-85.1) <HBr (-66.8) <HI (-35.4) b) Explain the following order of connection distance (pm): HF (92) <HCl (127) <HBr (141) <HI (161) Homework Equations xxx The Attempt at a Solution a) HF does hydrogen...
  10. Decimal

    Relation between temperature and boiling point?

    Hello, I am encountering some confusion with the relation between the latent heat of vaporization and the temperature of a substance. I understand both the latent heat and the entropy change of vaporization are dependent on the temperature, assuming the pressure is held constant. However given...
  11. dromeascr

    What is the pressure surrounding a liquid at its boiling point?

    Hello everyone, before I start I just want to mention that I am not an expert in physics whatsoever, so please be as specific as you can get if you wish to provide an answer. (The question itself might be considered stupid to be honest) I read the definition of the boiling point recently and...
  12. Z

    Why is the boiling point of 2-propanol lower than 1-propanol

    Homework Statement Why is the boiling point of 2-propanol lower than 1-propanol? The Attempt at a Solution Is this right? Because 2-propanol has its hydroxyl group in the middle of the atom, the electrons are all moving to the centre of the atom as opposed to 1-propanol, which has the...
  13. D

    Effect of impurities on the boiling point of ethyl ethanoate

    After carrying out reflux and distillation to produce ethyl ethanoate (ethyl acetate) I measured the boiling point and I got 71 degrees Celsius whereas the true value is 77.1 degrees Celsius. Impurities increase the Boiling point (BP) as well as concentration. However my calculates BP is lower...
  14. A

    Effect of a soluble volatile impurity on the boiling point?

    Hi everyone, just wanted to know how does a soluble, volatile impurity affect the boiling point of a liquid? I know it depends on the difference between the boiling points of the liquid and the impurity, but I'm afraid i still didn't get the point. Thanks
  15. Enigman

    Looking for a low boiling point solvent for MAPI precursors

    Things I have thought of till now: Acetonitrile with HI additive Acetonitrile with DMSO additive The problem with the first would be that HI is in an around 55% aqueous solution and water doesn't play well with the perovskite. Meanwhile, the second might end up needing enough DMSO to...
  16. D

    Exploring the Effects of Vacuum Pressure on Boiling Oil | Dilip

    Hi, We have seen water boiling at low pressures (vacuum jars), Will Oil also boil the same way in vacuum jar? Dilip
  17. G

    Resources for finding boiling point at other than 1 atm?

    I would appreciate it if someone could recommend something. I found a boiling point calculator by CalcTool but it doesn't seem that reliable.
  18. B

    How volatile impurity affects boiling point of a liquid?

    I know that non volatile impurities increases the boiling point of a liquid. Does volatile impurity decreases the boiling point? How?
  19. A

    Effect of particle size on boiling point in solution

    Hello. Suppose you dissolve something in water. I know that the boiling point should increase because as the water boils the solute's entropy decreases, and the net entropy should increase. Now suppose, that I dissolve GI chlorides in the water. Each solution of the salt has the concentration...
  20. R

    Why is vaporisation rate increased by a decrease in pressure

    In my textbook, it says that the rate of vaporisation can be increased by (a) increasing the temperature or (b) reducing the pressure. I understand why an increase in temp can lead to more molecules breaking away from the liquid and entering the vapor state. More temp = more energy = more...
  21. S

    Esters' high boiling point

    Why does 3-methylbutyl ethanoate have a higher boiling point than 3-methylbutan-1-ol and ethanoic acid? Attempt at a solution: I know that the ester has a marginally greater molar mass but I wasn't sure if this is the only deciding factor, particularly considering the strength of the other...
  22. D

    Melting point and boiling point

    Why there is huge difference in M.P. and B.P. Of Oxygen (M.P. - 54K,B.P.- 90K) and sulphur (M.P. - 393 K, B.P. - 718 K)
  23. T

    Why the temperature remains constant at the boiling point?

    Why all liquids vaporize on boiling point instead of the temperature gradually increasing along with vapor pressure and more liquid atoms evaporating? Does it have anything to do with formation of vapor bubbles?
  24. T

    Highest boiling point between organic compounds

    Homework Statement The following substances have approximately the same relative molecular mass. Which is likely to have the highest boiling point? Homework EquationsThe Attempt at a Solution I chose E as it has OH so therefore hydrogen bonding. Is this correct? Cheers!
  25. T

    Why does arsenic sublimate, while gallium melts?

    What does it tell you about a substance? A hight melting and boiling point means that the molecules hold together strongly, as in tungsten. A low melting point, as in hydrogen, means they're kinda loose. But what does the distance between them tell you? Something something entropy yadda yadda...
  26. Biker

    I Understanding Boiling Point Elevation: Real Gas Law and Its Impact on Molecules

    So was thinking a little bit about the ideal gas law. ##P V = n R T## And I read an article about the real gas law where they just edited few properties. ##(P + \frac{n^2 a}{v^2}) (V - nb) = n R T ## Where a and b are constant determined experimentally. So going back to our original point, Why...
  27. S

    Which has the highest boiling point?

    Homework Statement Which one of these had the highest boiling point? A. 3-Pentanone B. 1-Butanol C. Butanal Homework EquationsThe Attempt at a Solution The answer should be 3-pentanone because 1- it's molecular weight is approx 76 compared to the other which has approx 64 2 - because of the...
  28. A

    What is the latent heat for medium carbon steel

    I'have searched a lot but could not find latent heat for any kind of medium carbon steel for latent heat from solid to liquid and from liquid to gas. Also I want to know the corresponding melting point and boiling point for that know of steel. Any link for a table would be greatly appreciated...
  29. A

    Why boiling occurs at fix temperature?

    Can anyone explain to me why does temperature of water remains constant while boiling in an open vessel or in general sense why phase transition is isothermal in nature?please give me answers from thermodynamic point of view also.
  30. C

    Boiling water without heat

    Hey everyone, I found this video on Youtube of this guy boiling water by reducing the pressure: I'm not sure how the gauge he's looking at works but I think this is the vacuum instrument he's using: https://us.vwr.com/store/catalog/product.jsp?product_id=4789427 ^It says that it provides...
  31. T

    Which Compound Has Highest Boiling Point?

    Homework Statement Of the following compounds, which has the highest boiling point? (A) CH3—CH3(B) CH3—CH2OH(C) CH3—COOH(D) CH3—COH(E) H2S Homework Equations - The Attempt at a Solution Chose C because is more polar with the 2 oxygens, however, the answer has conflicting answer. It...
  32. S

    Intermolecular forces and boiling point

    I've come to understand that intermolecular forces cause the boiling point of hydrochloric acid solutions below 20% to be higher than the boiling point of water. I also understand that dissolving hcl in water is an exothermic reaction. But, what about those intermolecular forces. I assume they...
  33. T

    How do solute particles increase boiling point?

    The question is: Which solution listed below is going to have the highest boiling point? A. 1.5 m NaCl B. 1.5 m AgCl C. 2.0 m C6H12O6 D. 2.0 m CaCl2 E. 1.0 m Al2(SO4)3 I chose D (which was right) because in a solution, the more solute particles there is the higher the boiling point (this is...
  34. E

    Organic chemistry boiling point

    Homework Statement State true or false: The boiling point of propanoic acid is less than that of n-butyl alcohol, an alcohol of comparable molecular weight. Homework EquationsThe Attempt at a Solution Is this just a question where you either know it or don't OR is there some argument based off...
  35. faiziqb12

    Boiling and distance traveled

    i have got a question with distillation . in distillation as we know the mixture is boiled and the mechanism then goes like substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top. i don't know why , but i am having...
  36. S

    How to calculate amount of vapor given q(t) and p(t)?

    Hi everybody, I am trying to build a small model which basically should be able output "mass flow of water vapor as a function of time" given following inputs: - initial mass liquid water m_l_0 [kg] - initial temperature of liquid water T_l_0 [°C] - initial pressure p_0 [Pa] - heat added as...
  37. ScepticAmatuer

    Boiling point of water heated via microwave

    I took about 100 ml of distilled water, put a small, clean rock in it (to prevent "bumping" or explosion) and heated it repeatedly in a microwave oven on high for 45 seconds. After each heating I checked the temperature of the water with a digital temperature probe. I did this 7 or 8 times...
  38. L

    Determining boiling point from vapour pressure

    Homework Statement When benzene freezes at 5.5 C its density changes from 0.879 g cm-3 to 0.891 g cm-3. Its enthalpy of fusion is 10.59 kJ mol -1. Estimate freezing point of benzene at 1000 atm Homework Equations Solid liquid boundary: p=p*+ΔHfus/ΔV ln(T/T*) The Attempt at a Solution From the...
  39. UMath1

    Boiling Point of Rubbing Alcohol Lab | In-Class Experiment

    In class, we did a lab to determine the boiling point of rubbing alcohol. We used a thiele tube filled with water and place a test tube attached to a thermometer w/rubber band in it. However, we never saw any signs of boiling. We conducted several trials, the temperature went all the way above...
  40. VoteSaxon

    Van der Waals and boiling point

    Homework Statement The bulb of a constant volume gas thermometer is immersed in an ice/water/water vapour mixture at equilibrium and the recorded pressure is 0.400 atm. It is then immersed in a boiling liquid and the pressure is 0.844 atm. Sufficient gas is then removed from the bulb such that...
  41. B

    Understanding Vapor Pressure in Open Systems

    I learned that vapor pressure is defined in a closed system, but some questions ask me to consider vapor pressure in an open system. How is vapor pressure defined exactly? And where is this pressure acting against? Also why is it that at the boiling point, the vapor pressure and the atmospheric...
  42. A

    Boiling point and vapour pressure

    Hi all, I am facing difficulty in understanding the reason behind the fact that a liquid boils when the atmospheric pressure is equal to its vapour pressure. We know that at the vapour pressure, the air and the liquid remain in equilibrium, so there's no net evaporation or condensation. So...
  43. A

    Why do sugars have higher boiling points than water?

    I recently heard about an interesting chemistry experiment I have yet to try. It involves boiling soda and watching the water rise and the sugars remain at the bottom of the pot. The reason being is sugars have higher boiling points than water. Thus, the water boils first, heats up, and rises to...
  44. K

    Dew point more important than boiling point

    I was thinking, the critical point between the liquid and gas phases is the dew point, not the boiling point, right? Melting/freezing on the solid/liquid boundary is analogous to evaporation/condensation on the liquid/gas boundary. Boiling is something totally different, and is not possible in...
  45. M

    Boiling point Atmospheric/hydrostatic pressure

    So I understand that you get boiling when the vapor pressure equals atmospheric pressure so that the vapor within the medium can overcome the atmospheric pressure pressing on the surface of the liquid, but how do the bubbles overcome the hydrostatic pressure from the water above the bubble. If...
  46. K

    Pressure and boiling point

    I'm given an expression for the pressure of air with height z, as P(z)=P(0)e^{(-mgz/k_bT)} Where m is the molecular weight of air. It's know that the pressure of water varies with height above sea-level due to the variation of the pressure of the air. The excercise is about to show that...
  47. Q

    Boiling point of ethers and alkanes

    My organic chemistry textbook says that ethers generally have higher boiling points than alkanes because of dipole-diole interactions, but why then does hexane have a higher boiling point than ethyl-propyl-ether? Is this principle then not true for larger alkanes with 5 or more carbons? Diethyl...
  48. S

    Density and Boiling Point?

    Just a random question. Is there a specific relationship between density and boiling point? If there is, what is it and why do they relate?
  49. Y

    Oil boiling point at vacuum

    What may be the boiling point (temperature) of a refrigeration POE oil at, let's say, 500 microns absolute pressure ?
  50. C

    Help interpreting molal boiling point constant.

    Hi, I'm trying to understand how to explain what the molal boiling point constant is, from interpreting the units (using an example) K_b =3,62K*kg*mol^-1 I would say "One mole of particles are heated up by 3,62kelvin per kg?" but something feels wrong abou saying it that way. Can someone...
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