We discuss one of the answers to the questions below. It seems like one of those basic science facts: Water boils at degrees Fahrenheit degrees Celsius , right? Well, not always. In fact, water will boil at about degrees in Denver, due to the lower air pressure at such high elevations. The boiling point of water, or any liquid, varies according to the surrounding atmospheric pressure. A liquid boils, or begins turning to vapor, when its internal vapor pressure equals the atmospheric pressure.
But pressure drops as you gain elevation — say, by driving from Los Angeles to Denver — because there are fewer air molecules pressing on you. In Denver, the atmospheric pressure is only about 12 pounds per square inch, compared with Putting a liquid in a partial vacuum also will lower its boiling point.
In La Rinconada, a mining town in the Peruvian Andes that, at more than 16, feet, is the highest permanently inhabited town in the world, water will boil at about degrees.
As the temperature of the water increases, the average speed of the water particles also increases. At some point, water molecules have enough energy to push back other water molecules in the liquid phase to form a bubble. But you have to have the water hot enough so that the particles are moving fast enough.
It's also about the vapor pressure. In order to keep the bubble from collapsing, the pressure inside the bubble must be equal to the pressure outside the bubble. Inside the bubble is the vapor pressure and outside is the water pressure. This means that for water to boil, the temperature must increase until the vapor pressure is equal to the outside pressure and a bubble can form.
What about that external pressure? That depends on two things. First, the water itself. In order for the water to not collapse, the deeper water must have a higher pressure. So, the water pressure depends on the depth, the density of water and the gravitational field since it's due to the weight of the water. For a typical glass of water, the pressure at 2 centimeters below the surface is only a 0. And that is the second thing that contributes to the total pressure—the atmosphere.
The atmosphere also pushes down on the surface of the liquid to increase the pressure in the liquid. Now for the fun part. What if I decreased the atmospheric pressure pushing on some liquid water? This would reduce the pressure in the liquid also.
If I reduce this pressure enough, I can bring it down to the same level as the vapor pressure. Now the water particles have enough energy to form their tiny little boiling bubbles—without the need to increase the temperature.
I can even get water to boil at room temperature. Yes, you need a vacuum pump and a strong container to get this to work—but you can do it. Notice that I hold onto the boiling water flask just to prove that it's not hot.
Trust me. Oh wait. You don't have to trust me. You can do this on your own. You just need one of these large plastic syringes. Get the syringe and put some water in it with very little air.
Now seal up the end and heat up the water just a little bit. Here you can see my version. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels.
Facebook Facebook Twitter Twitter. Updated October 06, Featured Video.
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