CrazyEngineers Archive
Old, but evergreen and popular discussions on CrazyEngineers, presented to you in read-only mode.
@anjali zendre • 21 Oct, 2012
is the boiling point of water is always 100'c it does not affect by atmospheric condition?
@Abhishek Rawal • 21 Oct, 2012 • 2 likes Let me simplify it,
If you're living in Antarctica, assume that temperature is -20 degree c, then more heat energy is required to evaporate water(here it has turned to ice) to vapor than a person living in Equatorial area(assume 30 degree c).

Mathematically,
Antarctica : -20-100=-120 degree c
Equatorial area : 30-100=-70 degree c

Constant doesn't changes (will still remain 100 degree c) as boiling point of water.
So, technically atmospheric condition doesn't affects constant value.
Only the entropy (or enthalpy or "Energy required to change from one state to another" .. i forgot the specific term) depends.
@anjali zendre • 21 Oct, 2012 y
Troll_So_Hard
Let me simplify it,
If you're living in Antarctica, assume that temperature is -20 degree c, then more heat energy is required to evaporate water(here it has turned to ice) to vapor than a person living in Equatorial area(assume 30 degree c).

Mathematically,
Antarctica : -20-100=-120 degree c
Equatorial area : 30-100=-70 degree c

So yeah atmospheric condition DO matter.
thanks...yes this is true...
but atmospheric condition is depend on pressure, humidity, temperature and height etc...so if we think about all those things then what will be effect on boiling point of water?
if we are considering any one place.n measuring the boiling point of water on different atmospheric condition.
@rahul69 • 21 Oct, 2012 • 1 like Actually 100 degrees is the boiling point of water based on fixed(standard) environment conditions. Changing other properties (eg Pressure) water can be made to boil below 100 degree C .😁 https://wiki.answers.com/Q/When_will_water_boil_at_a_temperature_less_than_100_degrees_Celsius
@zaveri • 21 Oct, 2012 The boiling point of water is also affected by the amount of impurities present in it.

the greater the impurities, the lesser becomes the boiling point.
@Jeffrey Arulraj • 21 Oct, 2012 only pure water in STP condition boils in such a temperature

What exactly is your problem in it

If you want to know what exactly happens the Vapour pressure of Water becomes equal to the liquid pressure in 100 C and so it boils
@The myth buster • 21 Oct, 2012 • 1 like The boiling point of water 1s 100 degree celsius only at 1 bar or 101.325 kPa pressure..if the pressure conditons change, the corresponding sturation temperature shall be the boling point of water.And as the saturation pressure value increases,Saturation temperature also increases.
@anjali zendre • 22 Oct, 2012
The myth buster
The boiling point of water 1s 100 degree Celsius only at 1 bar or 101.325 kPa pressure..if the pressure conditions change, the corresponding saturation temperature shall be the boiling point of water.And as the saturation pressure value increases,Saturation temperature also increases.
yes..i was want to know about pressure condition....so water will boil in 100'c when atmospheric pressure is there...if pressure will change...boiling point of water will also Chang... means high pressure have low boiling point...and in higher latitude have low pressure so boiling point temperature will inc res...
@The myth buster • 22 Oct, 2012 • 1 like
anjali zendre
yes..i was want to know about pressure condition....so water will boil in 100'c when atmospheric pressure is there...if pressure will change...boiling point of water will also Chang... means high pressure have low boiling point...and in higher latitude have low pressure so boiling point temperature will inc res...
well as the altitude increases,pressure drops and so does the value of saturation temperature..refer steam tables for saturated water..!!
@LEO GEORGE • 11 Nov, 2012 • 5 likes yes,when pressure increases boiling point increases,when it drops boiling point also decreases,when altitude increases pressure drops so water boils below 100 degree ,by using steam tables we can find the boiling point for corresponding pressure's,this boiling point and pressure theory also used in pressure cooker .......
@Ankita Katdare • 12 Nov, 2012 Really cool answers in this thread. 👍 An easy way to remember is -
Water boils at 100 degree Celsius at sea level i.e. at standard atmospheric pressure. So up a mountain, where the air pressure is reduced, water boils at a lower temperature.
@Amith Gupta • 19 Nov, 2012 did you know that water could be burnt or exploded by enormous pressures at room temperature itself ? it all depends on pressure and temperature resulting . it can be done by just exposing it to a high frequency.
@solar morpher • 19 Nov, 2012
This curve is the reason for the strange behaviour of water in different conditions
@PuneetVerma • 22 Nov, 2012 • 1 like No..Boiling depends upon Saturation temperature which is different for different pressures... 100 degree Celsius is boiling at 1 atmospheric pressure.
@Jeffrey Arulraj • 22 Nov, 2012 The curve takes all the three parameters which are used to determine the temperature which water boils
@Saugata • 25 Nov, 2012 Water can boil even at 273.16 K. It's greatly affected by the pressure. Go through the T-s diagram or the mollier diagram to know more about it. (You will find it in any book on Thermodynamics.) You can also go through the topic "Triple point of water".
@Ramani Aswath • 25 Nov, 2012 • 1 like
zaveri: the greater the impurities, the lesser becomes the boiling point.
Actually boiling point is elevated by impurities.
https://www.chem.purdue.edu/gchelp/solutions/eboil.html

@anjali zendreyes..i was want to know about pressure condition....so water will boil in 100'c when atmospheric pressure is there...if pressure will change...boiling point of water will also Chang... means high pressure have low boiling point...and in higher latitude have low pressure so boiling point temperature will inc res...
Just two days back we were calibrating a new thermistor device that we were developing. We first measured the boiling point of water as a check of the meter. We got a value of 96.1 degC at Hosur, Tamilnadu, where the unit is located. For the altitude of Hosur we should have got 96.7 degC. Since we needed an accuracy of 0.1 degC, this was unacceptable.

I suddenly realised that the weather report predicted rain and checked the atmospheric pressure. This was less than the normal value for Hosur on that day, which was the reason for the apparent discrepancy. Heaving a collective sigh of relief, we got on with the work.
Here is a useful online steam table. You can plug in your conditions ant get the full steam data.

https://www.efunda.com/materials/water/steamtable_sat.cfm
@grsalvi • 25 Nov, 2012 • 1 like As everyone said : the boiling point of water is not constant as it is dependent on the pressure also.

I will add to this thread a very common example : Pressure cooker.

The Pressure cooker works on the same principle that is , the boiling point of a fluid can be changed by changing the pressure.

Hence in pressure cooker by increasing pressure , boiling point of water is increased (above 100 deg C),this helps in cooking the food at high temperature .

Therefore , food gets ready much faster in pressure cookers.
@Ramani Aswath • 25 Nov, 2012 • 1 like
grsalvi
I will add to this thread a very common example : Pressure cooker. Therefore , food gets ready much faster in pressure cookers.
I work with them day in and day out. Cookers that are exported do not whistle, because that loud sound frightens the user into thinking something is wrong. Export cookers use what is known as a hissing weight. This maintains a constant pressure inside and therefore a constant temperature. On the other hand a whistling weight valve, which lets the housewife watch a Mother-in-law daughter-in-law sitcom while she keeps an ear cocked to the whistle, is an Indian abomination. The whistle is created by the steam escaping out of a weight designed to rise at a particular pressure and drop back once the pressure falls to a designed value. In the mean time all that steam that escaped carries away considerable energy. What is worse is that the temperature also falls along with the pressure, which leads to a longer cooking time.
Unfortunately no Indian housewife will buy a non whistling cooker even when these are explained. I have not estimated the total power wasted in the above 250,000,000 cookers whistling away to glory every morning and evening across India.
@anjali zendre • 03 Dec, 2012
Really cool answers in this thread. 👍 An easy way to remember is -
Water boils at 100 degree Celsius at sea level i.e. at standard atmospheric pressure. So up a mountain, where the air pressure is reduced, water boils at a lower temperature.
thanks.. frnd.
@anjali zendre • 03 Dec, 2012
Amith Gupta
did you know that water could be burnt or exploded by enormous pressures at room temperature itself ? it all depends on pressure and temperature resulting . it can be done by just exposing it to a high frequency.
interesting frnd..

solar morpher

This curve is the reason for the strange behaviour of water in different conditions
yesss. i can feel the meaning.. thanks.

Saugata
Water can boil even at 273.16 K. It's greatly affected by the pressure. Go through the T-s diagram or the mollier diagram to know more about it. (You will find it in any book on Thermodynamics.) You can also go through the topic "Triple point of water".
very very nice thanks for all information..

bioramani
I work with them day in and day out. Cookers that are exported do not whistle, because that loud sound frightens the user into thinking something is wrong. Export cookers use what is known as a hissing weight. This maintains a constant pressure inside and therefore a constant temperature. On the other hand a whistling weight valve, which lets the housewife watch a Mother-in-law daughter-in-law sitcom while she keeps an ear cocked to the whistle, is an Indian abomination. The whistle is created by the steam escaping out of a weight designed to rise at a particular pressure and drop back once the pressure falls to a designed value. In the mean time all that steam that escaped carries away considerable energy. What is worse is that the temperature also falls along with the pressure, which leads to a longer cooking time.
Unfortunately no Indian housewife will buy a non whistling cooker even when these are explained. I have not estimated the total power wasted in the above 250,000,000 cookers whistling away to glory every morning and evening across India.
it's realiy interesting information..thanks for this.
@gdchethan • 20 Feb, 2013 • 1 like answer is no ................. boiling point of water is 100* C at 1 bar pressure
best example is pressure cooker if u cook in open pan ..............water starts to boilat 100* c so maximum temp water can attain is 100*c wat happens in pressure cooker is as u increase the pressure boiling point also increase that means water can attain around 120* without converting to vapour so vegetables or rice in water can get more heat ...........`so as u increase pressure boiling point increases
@ABHINAV RANJAN • 23 Feb, 2013 This you can get answered with simple question:
Why it's difficult to cook rice in hilly areas i.e, on mountains compared to plain areas?

When you read the book it's written that all the parameter are under STP conditions. It will vary if any of the conditions change
@gokulbudy • 24 Feb, 2013 boiling point is directly propotional to vapour pressure
vapour preassure means the pressure of each water molecule
@Ramani Aswath • 25 Feb, 2013
gokulbudy
boiling point is directly propotional to vapour pressure
vapour preassure means the pressure of each water molecule
Saturated steam pressure increases non-linearly with boiling point.
A single molecule cannot have any pressure.
@gohm • 26 Feb, 2013 Great thread! I moved it here into the chemical section from the mechanical section as it is a better fit here.
@simplycoder • 10 Mar, 2013 I am not the best person here to comment on this topic, but would amount of salt present in water affect the boiling point?
I think this comes under category of colligative properties
@Ramani Aswath • 10 Mar, 2013 Non volatile solutes elevate the boiling point as the solvent molecules are restricted from free vaporization by the non volatile molecules.
https://www.chem.purdue.edu/gchelp/solutions/eboil.html
@Allan Hugo • 13 Mar, 2013 Yes, this is called boiling point elevation, one of those colligative properties (melting point depression, and osmotic pressure too). Any decent chemistry book should have this discussion.
bioramani
Actually boiling point is elevated by impurities.
The relationship of pressure with temperature is specified by Antoine's Equation. Here is an online calculation:

https://ddbonline.ddbst.de/AntoineCalculation/AntoineCalculationCGI.exe

If you put water and the temperature at 100 deg C, the pressure results to 760 mmHg which is equivalent to 1 atm. For different atmospheric pressure values there corresponds a temperature where the vapor pressure of the substance is equal to that of the atmospheric pressure. This temperature is called the boiling point of the substance at that specified pressure.
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