Does water boil faster or slower on a mou ntain top where air pressure is lower?
451840
Quite obviously faster. To boil over and turn to vapour, the water molecules near the surface need a lower amount of energy when the water is being boiled in a rarer atmosphere.
625586
The actual reason that alcohol evaporates quicker than water has to do with vapor pressure.\n\nAll liquids have a certain amount of vapor at the surface of the liquid.  Since the intermolecular forces are weaker within a smaple of alcohol than within a smaple of water, there is more vapor present above the surface of alcohol than above the surface of water. The more vapor above the surface, the higher the vapor pressure.  The higher the vapor pressure, the faster the rate of evaporation. \n\nSince there is more vapor present above the surface of the alcohol, more molecules will randomly leave the surface and go into the air surrounding the container.  This is the process of evaporation, which is different than boiling.  The two are related, but not the same.\n\nThis difference in rates of evaporation has nothing to do with the heat capacities of water and alcohol.
4765
Boiling is very rapid evaporation starting at the bottom of a container of water.\n\nEvaporation occurs fastest where there is the most heat (energy).  When we heat water to make it boil we heat it from the bottom so the evaporation occurs at the bottom of the pot.  As a result, large  bubbles of water vapor form at the bottom and rise to the surface in the boiling action.  If we applied the same heat to the top surface of the water it would evaporate just as quickly but we would not call it boiling because the bubbles would not form and rise to the surface.\n\nNormally evaporation occurs at a much slower rate than boiling because most evaporation occurs with room temperature water.\n\nEvaporation-is the escape of molecules from the liquid state to the gas or vapor state. In evaporation, molecules of higher-than-average kinetic energy escape from a liquid, leaving it cooler than it was before they escaped.\n\nBoiling-is the temperature at which the vapor pressure of a liquid is equal to the \nexternal pressure above the liquid.  When we give the boiling point of a liquid, we \nneed also to state the pressure.
48898
when a liquid boils, it literally turns into a gas (steam).  As the water at the top of the pot evaporates, the gas can go straight into the air. But when it evaporates (boils) at the bottom of the pot, it forms bubbles that have to float up to the top
15822
It mainly depends on the pressure (if we are talking about pure water). The higher the pressure, the higher the boiling point - it can be much lower (ex. high in the mountains) or much higher than 100 degrees C (the boiling point under normal atmospheric pressure). If we don't talk about pure water, then adding other chemicals (for example, table salt - sodium chloride) can raise the boiling point as well.
22783
The bubbles are not "air" as most of the other answers claim; they are gaseous water, otherwise known as steam.  reverie's assertion about water pressure is also incorrect.  In a pot, the bubbles primarily form at the bottom of the pan because that's the hottest part of the pan and water.  The water there gets above the boiling point (212 F) and changes to steam.  At first, surface tension keeps the bubble stuck to the pan. But when enough steam is generated to make the bubble large enough, the bouancy of the bubble forces it to rise to the surface.
115707
It depends on the pressure and temperature of the water so the previous answer is limited to only one condition.
109177
i believe its because the boiling point of water is only 212 at normal atmospheric pressure, so if the pressure is changed the boiling point does too.
168739
Definitely. For several reasons. One, you save energy. The boiling temperature of any liquid remains the same no matter how much heat you put into it. (A pressure cooker's case is different.) The added heat simply turns the liquid into gas (steam). And, second, the more energy you put in there, the more violent the evaporation becomes. You don't want your soup frothing out of the pan or your food to burn. So follow your mother and keep it at low.
731331
I've heard that its the boiling water that freezes first. \n\nI think because the water molecules are hot (i.e. they are moving fast) the energy (or heat) will escape (move to equilibrium with other items in the freezer) at a faster rate than the water molecules in colder cup of water. \n\nBut really I'm mostly guessing with my explanation.
993259
Boiling point of anything is dependent on pressure.... higher the pressure lower the boiling point...\nWhen you try to boil an egg on mountain.. coz the pressure there is quite low.. it take longer for water to boil and thus egg.
878988
This depends upon how dirty the water is.  If the dirty water is clogged with material bits then that will slow it down.  If the dirty water is dirty in color only it should be equal.
619043
I'm assuming you mean boil an egg. \n\nAt sea level where the atmospheric pressure is 1 atm (at stp) water boils at 100 degrees celcius. This is sufficiently hot enough to boil an egg.\n\nAs you rise higher in altitude, there is less air above you and so the atmospheric pressure becomes less. This allows gases to escape from liquids more readily (a can of coke is pressurized to 4 atm's). As a result, the water will boil more readily at a higher altitude, however, it will do so at a lower temperature than it would at sea level, so it would take the egg longer to cook.
968042
Boiling is vapour pressure phenomenon. A liquid always exerts a pressure in the space just above it due to evaporation of its surface molecule which is called vapor pressure of that particular liquid and as temperature is raised the vapour pressure goes on increasing. When vapor pressure of the liquid exceeds atmospheric pressure liquid starts to boil.\nin case of a mixture, the solute molecules bind the molecules of the solvent and thus there are fewer surface molecule available to evaporate from the liquid surface. Due to which vapour pressure exerted by a mixture is always less than vapor pressure of pure solvent. To make vapor pressure of mixture to reach the atmospheric pressure level its temperature should be raised more than temperature of solvent alone. Thats why a mixutre has a boiling point elevation.
299546
water "boils" when the Kinetic energy (energy of motion and heat) cause the molecules of water to expand or separate far enough away that it changes from a liquid to a gas. The greater the force keeping the molecules together, the more energy it needs. On Earth, the force is air pressure. At sea level where the pressure is greatest, water boils at about 100 degrees Celsius. Up in the mountains at 7000 feet it would boil at 80 -90 degrees or even less. In space even the smallest amount of energy would cause it to "boil".\nIt takes one calorie to raise one gram of water one degree Celsius. If you trap the water in a container, you can get the heat of the water much higher than the boiling point. But it could explode if the container is too weak to handle the pressure. So don't try it.
2167
You can't make water boil by compressing it directly.  If you compress it, but allow the hest caused by compressing to leave, then you'll get nothing.  It is possible if you have an insulated system to compress it in such a way that temperature of the water rises, but at higher pressures, the temperature needed to boil water increases.  If the water, once heated by comprsession, were to be rapidy brought to a lower pressure through a throttling valve, it could be vaporized.\n\nBut really, if you want water to boil, you should *DECREASE* the pressure.  In out space, water at room temperature would instantly boil due to the low pressure involved.
842532
Water or milk does the same thing on boiling. It's heated at the bottom by the burner, and rises to the top, creating a circular motion. It is probably more visible with milk. By the way, most of what makes milk a liquid, is water