What is Boiling: Definition and 319 Discussions

Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. At sea level the boiling
point of water is 100 °C or 212 °F but at higher altitudes it drops to correspond with decreasing atmospheric pressures.
Boiling water is used as a method of making it potable by killing microbes and viruses that may be present. The sensitivity of different micro-organisms to heat varies. But if water is held at 100 °C (212 °F) for one minute, most micro-organisms and viruses are inactivated. Ten minutes at a temperature of 70 °C (158 °F) is also sufficient for most bacteria.
Boiling water is also used in several cooking methods including boiling, steaming and poaching.

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  1. K

    Deriving the Relationship Between Pressure, Boiling Point, and Height

    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...
  2. C

    Why doesn't boiling water exceed 100 deg C?

    I know that water can be superheated, but my question is more fundamental. What causes water to boil at 100 deg C? I know that there are several factors (atmospheric pressure, nucleation sites, hydrogen bonding, surface tension, etc) but that's not what I'm getting at. I'm interested in the more...
  3. L

    Boiling liquid in a sealed container

    Suppose I have a sealed container of fixed volume containing 3/4 air and 1/4 of some liquid by volume at room temperature (22C). I wish to boil the liquid by applying external heat. As I apply heat to the container, the pressure inside the container will rise, which will change the boiling...
  4. mrspeedybob

    Uncovering the Mysteries of Sauteing Onions in Boiling Sugar

    I have a recipe that begins with sauteing onions in boiling sugar. It occurred to be today that I don't know what the vapor is that the sugar is giving off when it boils. There is no water in the pan at that point (other then what is in the onions). Are the bubbles that I'm seeing actually...
  5. Maxo

    Boiling Food: Is Less Boiling More Efficient?

    Look at this example. I understand the reasoning here, in order to save energy one only needs to boil water slightly. But doesn't it also take longer time to boil it the same amount? I'm pretty sure in a given number of minutes, the spagetti will be more ready (more cooked) if it has been...
  6. M

    UV Transparent Boiling Flask Search

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  7. 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...
  8. R

    Boiling Water Faster in Increments?

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  9. S

    Is There a Relationship Between 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?
  10. Y

    What Is the Boiling Point of POE Oil at 500 Microns Pressure?

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

    Calculating Power Required to Heat Water at a Rate of 21s^{-1}

    Hello, my problem is this It is possible to buy water heaters that provide ‘instant boiling water’ at the turn of a tap. Assume the heater takes in water at 4^{\circ}C and gives out hot water at 100^{\circ} C. Furthermore, assume that the hot water flows out at a rate of 21s^{-1} How much...
  12. A

    Rate of reactions with eggs boiling

    At a high altitude camp in the Rockies, water boils at 95.4°C instead of 100.0°C. A visitor has requested a soft-boiled egg (usually boiled for 3.00 minutes at 100.0°C). The activation energy for the reaction in question is 453 kJ/mol. 6 marks egg protein (l) egg protein (s) How long will it...
  13. 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...
  14. B

    Vapor Pressure, Open Container, and Boiling

    I've been confused about this for a while now and haven't found anything that directly addresses this problem. Please correct any faults you see in my reasoning. My understanding of vapor pressure is that it is the pressure exerted by the vapor phase of a substance above the liquid phase...
  15. J

    Does Boiling Water Faster Depend on Amount or Incremental Additions?

    Hi guys First time posting on here. Family and I were having dinner and a discussion came up. If I need to boil 1000ml of water, would it boil faster if I boil all 1000 ml at once or if I boil say 200ml, wait for it to boil, add another 200 , let it boil and add another 200 till there's...
  16. Q

    Understanding Phase Diagrams: Boiling, Melting & Critical Points

    Homework Statement https://scontent-b-dfw.xx.fbcdn.net/hphotos-prn1/v/1012733_10201076259690370_236735593_n.jpg?oh=4896ca67a34d3b223b764aba8ed308ab&oe=528A1B57 Homework Equations http://upload.wikimedia.org/wikipedia/commons/3/34/Phase-diag2.svg The Attempt at a Solution Not sure entirely...
  17. C

    Which statement applies to boiling but not to evaporation?

    "Which statement applies to boiling but not to evaporation?" Homework Statement Which statement applies to the boiling but not to the evaporation of a liquid? A The separation of the molecules increases greatly B At normal atmospheric pressure, the process occurs at one temperature only. C...
  18. Q

    Boiling and Freezing Points of Solutions

    Homework Statement The aqueous solution with the lowest freezing point of the following group is: 1) 0.01m MgSO4 2) 0.01m NaCl 3) 0.01m CH3CH2OH 4) 0.008m MgCl2 5) all equal Homework Equations Solutions have lower freezing points and higher boiling points than their solvents...
  19. S

    How does the efficiency of a reactor affect the amount of power it produces?

    Homework Statement A boiling water reactor has a mass flow rate of 1266.4 kg/s. The water enters the reactor at 250 °C. It boils at 291.5 °C. It exits the core at 500 °C. The specific heat of water at 7.5 MPa is 4.380 kJ/kg/°C, the latent heat of vaporization is 2357 J/kg and the specific...
  20. teroenza

    Calculate new boiling point with change post-pressure change

    Homework Statement Liquid X boils at 127C, at a pressure of 10.6*10^5 Pa. Its enthalpy of vaporization is 5000 J/mol. At what temperature will it boil if the pressure is raised to 1.08*10^5 Pa? Homework Equations \frac{dT}{dP}=\frac{l}{T(v_{B}-v_{A})}The Attempt at a Solution It seems so...
  21. S

    Why does melting and boiling occur at a specific temperature?

    When a solid is heated, its kinetic and potential energies increases. Up to a certain point, the kinetic and potential energy is so high that any heating done to it would only increase the potential energy and not the kinetic energy of the solid anymore. When this happens, some of the...
  22. V

    Understanding the Difference Between Evaporation and Boiling

    Hello, This is basic stuff and I feel a bit embarrassed for asking this, but here goes: From what I think I know, evaporation is always happening in a liquid (water, for example) irrespective of the vapor pressure, but boiling only occurs when the vapor pressure is equal or greater than the...
  23. C

    Latent heat in water vapor below boiling

    Hi - I'm a physics newbie so this is an elementary question, but I can't find the answer with a google search. Water evaporates at a wide range of temperatures, what is the latent heat in the water vapor (in calories or Joules), for example, at 30°C, 60°C? Assume standard atmospheric...
  24. J

    Why does 2-propanethiol have a lower boiling point than 1-propanethiol

    Homework Statement Consider 2-propanethiol, shown below. Would you expect its boiling point to be higher or lower than that of 1-propanethiol? Why?Homework Equations 1-propanethiol: 2-propanethiol: The Attempt at a Solution I looked it up, and 2-propanethiol does have a lower boiling point...
  25. J

    Boiling points and explanation

    Homework Statement Arrange compunds in order of increasing boiling points and explain why. C2Br6,C2F6,C2I6,C2Cl6 Homework Equations The Attempt at a Solution I have C2Cl6 < C2Br6 < C2I6 < C2F6 My explanation is as follows. C2F6 is highest because it has dipole dipole forces...
  26. N

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    Just curious, When my mom was boiling water i saw that the rate of bubbles coming out of water was increasing as time passed.But i want what is the rate of bubbles coming out is proportional to? And one thing i noticed is that when the gas is shut off the bubbles stop instantaneously.Why is it?
  27. F

    What is the difference between water evaporation and boiling?

    I have recently wondered how water can dry at normal, livable temperatures, but its boiling point is 373.15K. Is there a difference between drying water and boiling it into a gas?
  28. S

    Vapor pressure of boiling water

    Why does the answer say that vapor pressure only depends on temperature and intermolecular forces substance experiences? I thought external pressure did affect vapor pressure because when you heat a pot of boiling water at higher elevation the boiling point decreases, and vapor pressure...
  29. C

    Can boiling and evaporation occur simultaneously?

    I understand the differences between evaporation and boiling as stated in secondary school textbooks. But I would like to know, can evaporation occur at or above the boiling point? I think that, since evaporation is the escaping of high energy molecules, then when the water is boiling, there...
  30. C

    Archived Finding a lot of answers to water boiling point.

    Homework Statement I had an issue with a professor a while ago. A question was asked, "Why does water boil at 100°C?". What I believe was the targeted answer was something around "Hydrogen bonds." Hydrogen bonds are a valid answer, I believe also correct enough. For clarity purposes, I...
  31. fluidistic

    Calculating the boiling temperature

    Homework Statement I'm stuck on the following problem: A particular liquid boils at 127°C at a pressure of 800 mmHg. It has a heat of vaporization of 1000 cal/mole. At what temperature will it boil if the pressure is raised to 810 mmHg?Homework Equations Clapeyron's equation...
  32. N

    Is boiling just high vapor pressure?

    Is boiling basically a really high vapor pressure?
  33. 1

    Vapor pressure given boiling point and heat of vaporization?

    Homework Statement What is the vapor pressure of benzene at 50.0 C? Benzene's boiling point is 80.1 C and its heat of vaporization is 31 kJ/mol Homework Equations The Attempt at a Solution I don't want to be that guy who just says "I don't know" but.. All I know is that: ln P...
  34. S

    Fluid's boiling point dependence as function of pressure

    Greetings to all, I need some help for i understand how to demonstrate fluids boiling point dependence as function of pressure (i.e for main cool agents). Which are the basic equations for to write a general formula? I know that in PHWR type reactor water is at hight pressure to prevent...
  35. W

    Heat Exchanger - Boiling Rate - HT Coefficient

    Homework Statement In Attachment Homework Equations The Attempt at a Solution Second Attachment. - I have only attempted part (i) so far, because I am not sure if I am doing it correctly. I was thinking since the value of the latent heat of pentane is given, surely it has to be...
  36. F

    Calculate freezing point depression and boiling point elevation

    Homework Statement Calculate new freezing point and boiling point when 0.47 mol ethylene glycol and 0.14 mol KBr is added to 150g H2O. Express your answer using one decimal place.Homework Equations molality = moles solute/kg solvent ΔTf=i*Kf*m ΔTb=i*Kb*m New bp = ΔTb + normal bp New fp =...
  37. S

    Boiling Ethanol & Using a kitchen exhaust hood instead of a fume hood

    Hi, I'm doing a lab at home on photosynthesis for biology, in which I have to boil leaves in ethanol, and I have a few questions about safety for this. First of all, is it at all safe to actually boil denatured alcohol/ethanol, especially where people might inhale it? And depending on how safe...
  38. D

    Boiling point of Cyclohexene and 2-methylbut-1-ene

    So i just took a final and the question was Arrange the following solvents in order of boiling point. water 2-methylbut-1-ene cyclohexane So the answer was Water>cyclohexene> 2-methylbut-1-ene. I understand by the hydrogen bonding that water is definitely #1. But I can't...
  39. A

    What factors affect the boiling point of polar molecules?

    arrange the boiling point of the following compounds methoxymethane,butane,pentane and water I quickly arrange like this butane<pentane<methoxymethane<water but after checking wiki,it should be methoxymethane<butane<pentane<water In my knowledge,methoxymethane is a polar molecule,so i...
  40. A

    Pasteurization temperature adjustment for boiling point variations

    If you are at altitude and let's say water boils at 95 Celsius. Pasteurization for an X food product is 30 minutes at 82 Celsius at sea level. Now deductively, should I also reduce my pasteurization temperature to 82-5=77 Celsius to compensate?
  41. A

    Why Does Water Boil at 96 Degrees in Pattaya, Thailand?

    I have tested this with 3 thermometers, 2 Taylor digitals and a candy thermometer... My water boils at 96 celcius and I'm in Pattaya Thailand with sea elevation of 8 meters... Actually slow boil at 93-94 and very heavy boil at 97-97 I'm perplexed...!
  42. W

    Boiling water more efficiently

    While boiling water, I was thinking: Would one liter of water boil faster or slower if I boil it all at the same time, or if I do it in stages, ie: First boil one deciliter, then add a deciliter and wait it to boil, and so on until there's one liter of boiling water. Stated a bit more...
  43. jaumzaum

    Some doubts I have while trying to compare boiling points/ solubility

    I was trying to compare some solubilities (in water) and some boiling points, and I could not explain it for some molucules. Also, I have some doubts in the theory itself. Why is 2-pentanone more soluble than pentanoic acid? Why is a ketone more soluble than the respective aldeyde...
  44. R

    Effect of air pressure on boiling point of water

    I know that the boiling point of water is lower when the atmospheric pressure is less (such as at the top of a mountain), but why is that? Once a water molecule has the energy to escape from the binding forces that keep it with the other water moelcules in the liquid, I don't understand why...
  45. A

    Boiling water to save energy, start a low or high gaz setting?

    What is more efficient to bring water to a boil? 1. Using the low setting on heat 2. Going full blast to get it to boil as fast as possible For a vehicle, developing velocity is more economical with slow accelaration, but would it be the same with boiling water? Does it take less BTU...
  46. T

    How does boiling exactly work?

    After hours of reading and googling, I still do not really understand how boiling works. I have some questions: What I know is that boiling occurs when the vapor pressure is equal to the atmospheric pressure. But I thought that vapor pressure is the pressure exerted by the water vapor...
  47. J

    Water Nucleate Boiling possibility in a fire tube Boiler

    Hi guys, I'm designing a simple waste heat recovery Fire Tube Boiler. The Flue gas inside the tubes has an average temperature of 300 C (572 F). The tubes are submerged in water at a pressure of 6 atm, this gives us the saturated steam temperature of 158.83 C ( 318 F). I've calculated The...
  48. Y

    Atmospheric Pressure & Boiling Point of Water: 20 C

    What does the atmospheric pressure have to be to make the boiling point of water 20 C?
  49. M

    Thermodynamics: dropping iron into thermos of nitrogen at boiling point

    Homework Statement You come into lab one day and find a well insulated 2000mL thermos bottle containing 500mL of boiling liquid nitrogen. The remainder of the thermos has nitrogen gas at a pressure of 1.0atm. The gas and liquid are in thermal equilibrium. While waiting for lab to start, you...
  50. Q

    Methanal vs Hexanone Boiling Point Comparison

    Which one has higher boiling point?Methanal or Hexanone?
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