Yes, You Can Boil Water at Room TemperatureSometimes it's right on the box of rice mix-the high altitude version of cooking instructions. Usually this means that your rice will have to cook a little bit longer if you are in Denve or at the top of Mount Everest. Of course that's just a joke. No one cooks rice at the top of Everest. But why are the instructions even different? Why does it matter where you cook? The answer has to do with boiling water.
You ask some people on the street about the boiling temperature of water. Some might say 212°F or even better 100°C-but that's not always true. As you increase your altitude above sea level, the boiling point of water decreases by about 1°F for every 500 feet increase. That means your water in Denver is going to be 203°F and this will have an impact on your cooking. But why?
Water Vapour Pressure
There are many awesome things about water-one interesting factoid is that on the surface of the Earth you can find water in all three phases: solid, liquid, and as a gas. We call the gas phase of wa- ter 'water vapour'.
You might think that you need to boil liquid water to create water vapour-but you do not. You just need some liquid water at room temperature. Picture a glass of water. If you could zoom in with super vision (not actually possible), you would see that this water is made of a bunch of molecules-water molecules. Although these molecules are themselves made of three atoms: two hydrogens and one oxygen. Let's just think of them as tiny balls.
These tiny water balls are moving around in the water but stay fairly close to their ball neighbours. This motion isn't due to currents in the water, instead this is thermal motion. Imagine these tiny balls jiggling around in a giant collection of balls: The hotter the water, the greater the motion of these water balls. But wait! The speeds of the water particles are not all the same. Although there is an average ball speed, some are going faster and some are going slower. It's just like the height of a group of adult humans. There is an average height, but everyone is not the same. Some people are very tall, but that's just a small fraction of the total group.
If you have a glass of water sitting out on a table, the water balls don't just stay as a liquid. Some of these balls have enough thermal energy to break away and become free. Free from the liquid stage means the water ball is now a gas-water vapour. Boiling is not needed to get this water vapour. But wait! It works the other way too. Some of the water balls in the gas stage can interact with the liquid water and join the liquid water balls.
Water in a closed container will eventually reach an equilibrium state between water vapour and liquid water. At this equilibrium state the rate that water balls are freed from the liquid state are the same as the rate of water balls entering the liquid state. The pressure of this water gas in equi- librium is called the vapour pres- sure. You can see evidence of this water vapour in a closed container by looking at the water that condenses on the walls.
Boiling Water
Here is what water looks like when you get it to 100°C in slow motion. Yes, I know you have seen this before. But it's still cool.
What are the bubbles in the boiling water made of?
Are the bubbles made of air? What about some hydrogen and some oxygen? No. The bubbles are water vapour-they are small pockets of water in the gas phase. I mean, they could not be air. Where would this air come from? The only option is that the bubbles are made of water vapour.
So, what is happening to make these boiling bubbles of water vapour? It's all about temperature and vapour pressure. 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.
But wait! It is also about the vapour 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 vapour pressure and outside is the water pressure. This means that for water to boil, the temperature must increase until the vapour 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 not to 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. For a typical glass of water, the pressure at two centimetres below the surface is only a 0.2 percent increase over the atmospheric pressure. 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.
Lower Pressure
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 vapour pressure. Boom. 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.
I used hot glue and a rubber stopper (along with a Lego piece) to seal the hole. The syringe was then heated to about 42°C (a little over 100°F).
Now I can pull the plunger out to decrease the pressure in the liquid and induce boiling.
It is pretty tough to pull the plunger back to decrease the pressure- but you can do it. Oh, why heat the water up? Well, I can not get a perfect vacuum by pulling the plunger, so I need a little boiling help by starting the water at a higher temperature.
This is exactly what's going on when you cook your rice at high altitude. Well, not exactly the same-there is not a human pull- ing back on a giant plunger that holds the air on Earth. The Earth's gravitational field does that for you..
- Rhett Allain
A. Find the words from the text that have the following meanings.
a. the height of an object or point in relation to sea level or ground level-altitude |
b. a group of atoms bonded together-molecule |
c. a state in which opposing forces are balanced-equilibrium |
d. to change from a gas or vapour to a liquid- condense |
e. a piece of unreliable information that is repeated so often that it is accepted as the factfactoid |
f. a space or container from which the air has been removed- vacuum |
g. a device that is used to remove blockages from the drain of a basin or tub- plunger. |
B. Complete the sentences with the correct words or phrases from the text.
a. Water bubbles break down if vapour pressure inside and outside the bubbles is equal. |
b. As the altitude goes up, the boiling point of water decreases. |
c. Random motion of molecules or particles is called thermal motion. |
d. If the door does not open, try pushing the key in the lock. |
e. Certain chemicals can induce undesirable changes in the nervous system. |
C. Answer these questions.
a. What is the speed of the water particles compared with? |
The speed of water particles is compared to the jiggling motion of tiny balls in a collection of balls. |
b. How are bubbles formed in the boiling water? |
Bubbles in boiling water are formed when water particles gain enough energy to push back other water particles and create a bubble. |
c. Mention two things on which external pressure depends. |
External pressure depends on the depth and density of water, as well as the gravitational field. |
d. How is the atmosphere related to the pressure of water? |
The atmosphere contributes to the pressure in the liquid water by pushing down on its surface. |
e. What would happen if the atmospheric pressure on the liquid water was decreased? |
If the atmospheric pressure on the liquid water was decreased, the pressure in the liquid would also decrease, potentially allowing it to boil at a lower temperature. |
f. What would the experimenter gain if s/he pulled the plunger out? |
If the experimenter pulled the plunger out, they would decrease the pressure in the liquid, which could induce boiling. |
Word Meaning
altitude /ˈæltɪˌtjuːd/ |
height, elevation |
The height above sea level. |
high /haɪ/ |
tall, elevated |
Being far above the ground or another surface. |
version /ˈvɜːrʒn/ |
edition, variant |
A particular form or variant of something. |
cooking /ˈkʊkɪŋ/ |
preparing, making |
The process of preparing food for eating by applying heat. |
instructions /ɪnˈstrʌkʃənz/ |
directions, steps |
A detailed step-by-step guide to follow in order to achieve a specific result or complete a task. |
Denver /ˈdɛnvər/ |
- |
A city located in the state of Colorado, United States. |
boiling /ˈbɔɪlɪŋ/ |
bubbling, simmering |
The process of liquid reaching its highest temperature and producing bubbles and vapor. |
vapour /ˈveɪpər/ |
steam, mist |
The gaseous form of a substance, typically when it is below its boiling point. |
molecules /ˈmɒlɪkjuːlz/ |
particles, atoms |
The smallest unit of a substance that retains the chemical and physical properties of that substance, consisting of one or more atoms bonded together. |
thermal /ˈθɜːrməl/ |
heat-related, temperature-related |
Relating to heat or temperature. |
motion /ˈməʊʃən/ |
movement, action |
The act or process of moving or being moved. |
jiggling /ˈdʒɪɡəlɪŋ/ |
shaking, vibrating |
Moving or causing to move with quick, small, jerky motions. |
giant /ˈdʒaɪənt/ |
enormous, colossal |
Extremely large in size or magnitude. |
condenses /kənˈdɛnsɪz/ |
liquefies, solidifies |
The process of a gas or vapor turning into a liquid due to cooling or increased pressure. |
bubbles /ˈbʌbəlz/ |
foam, froth |
Small spheres of gas enclosed in a liquid or solid, typically caused by the release of air or vapor. |
pressure /ˈprɛʃər/ |
force, stress |
The continuous physical force exerted on or against an object by something in contact with it. |
atmospheric /ˌæt.məˈsfɪr.ɪk/ |
air, aerial |
Relating to the Earth's atmosphere. |
vacuum /ˈvæk.juːm/ |
empty space, void |
A space entirely devoid of matter, such as gas or air. |
pump /pʌmp/ |
compressor, device |
A mechanical device used to move fluids or gases by mechanical action. |
syringe /ˈsɪrɪndʒ/ |
injector, needle |
A small tube with a hollow needle used to take in or release fluids, especially for medical purposes. |
plunger /ˈplʌndʒər/ |
piston, rod |
A part of a syringe that can be moved up or down to draw in or push out fluids. |
induce /ɪnˈdjuːs/ |
cause, trigger |
To bring about or stimulate a process or action. |
gravitational /ˌɡrævɪˈteɪʃənəl/ |
gravitational force |
Relating to the force of attraction between objects with mass. |
Extra Questions to Practice
Expandable FAQ Section
Why might cooking instructions be different for rice at high altitudes?
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Cooking instructions might be different for rice at high altitudes because the boiling point of water changes with altitude.
What are the three phases of water that can be found on Earth's surface?
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The three phases of water found on Earth's surface are solid (ice), liquid (water), and gas (water vapor).
How can water molecules in a glass of water be described?
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Water molecules in a glass of water can be described as tiny balls made of three atoms: two hydrogens and one oxygen.
What causes the tiny water balls in the glass to move around?
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The motion of the tiny water balls in the glass is caused by thermal energy or heat.
Can water vapor be created without boiling liquid water?
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Yes, water vapor can be created without boiling liquid water; some water molecules can break away from the liquid and become free as water vapor.
What happens when water in a closed container reaches an equilibrium state?
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When water in a closed container reaches an equilibrium state, the rate at which water molecules enter and leave the liquid is the same, and it is called vapor pressure.
What are the bubbles in boiling water made of?
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The bubbles in boiling water are made of water vapor, not air.
How do bubbles form in boiling water?
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Bubbles in boiling water form when water molecules have enough energy to push back other water molecules and create pockets of water vapor.
Why does water need to reach a certain temperature to boil?
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Water needs to reach a certain temperature to boil because the vapor pressure inside the bubbles must be equal to the outside pressure.
What determines the pressure inside the bubbles in boiling water?
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The pressure inside the bubbles in boiling water is determined by the vapor pressure of water.
How does the depth of water affect its pressure?
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The pressure in water increases with depth due to the weight of the water above.
What else contributes to the total pressure in water?
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The atmosphere also contributes to the total pressure in water.
Can water be made to boil at room temperature?
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Yes, water can be made to boil at room temperature under specific conditions like reducing the atmospheric pressure.
How can water be made to boil at room temperature?
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By decreasing the atmospheric pressure on the liquid water, it can boil at room temperature.
What happens when the pressure on the liquid water is reduced enough?
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When the pressure on the liquid water is reduced enough, it can reach the same level as the vapor pressure, and boiling occurs at a lower temperature.
Why does reducing the pressure on the liquid water induce boiling?
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Reducing the pressure on the liquid water allows the water particles to have enough energy to form tiny boiling bubbles.
What evidence shows the presence of water vapor in a closed container?
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The condensation of water on the walls of a closed container is evidence of the presence of water vapor.
Can you create a vacuum to make water boil at room temperature?
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Yes, by using a vacuum pump and a strong container, you can create a low-pressure environment for water to boil at room temperature.
Is it necessary to heat the water before reducing the pressure to induce boiling?
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Yes, heating the water initially helps to provide enough thermal energy for boiling to occur.
Can you demonstrate water boiling at room temperature using a plastic syringe?
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Yes, by heating the water in a sealed plastic syringe and then reducing the pressure, you can observe boiling at room temperature.
Why is it important to have a strong container when creating a vacuum to boil water at room temperature?
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A strong container is necessary to withstand the low pressure created by the vacuum.
How does the gravitational field contribute to the pressure of water?
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The gravitational field affects the pressure of water based on its depth and density.
Can water boil at a lower temperature at higher altitudes?
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Yes, water boils at a lower temperature at higher altitudes due to the reduced atmospheric pressure.
What is the relationship between temperature and the speed of water particles?
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As temperature increases, the speed of water particles also increases.
Why does boiling occur when the vapor pressure is equal to the outside pressure?
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Boiling occurs when the vapor pressure inside the bubbles matches the pressure outside, allowing the bubbles to form and rise.
What happens to the boiling bubbles if the pressure inside them is lower than the outside pressure?
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If the pressure inside the boiling bubbles is lower than the outside pressure, the bubbles collapse.
Can water exist in all three phases simultaneously?
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No, water cannot exist in all three phases (solid, liquid, and gas) simultaneously under normal conditions.
Can you observe water in the gas phase without boiling it?
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Yes, water vapor can be observed without boiling liquid water by having some liquid water at room temperature.
Why is it important to consider altitude when cooking rice?
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Altitude affects the boiling point of water, so cooking instructions may need adjustment to ensure proper cooking at different altitudes.
What would happen if you tried to boil water in a completely sealed container without adjusting the pressure?
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If you tried to boil water in a completely sealed container without adjusting the pressure, the pressure inside the container would increase, and an explosion could occur.
Can water boil at room temperature in outer space?
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Yes, in the vacuum of outer space, where there is no atmospheric pressure, water can boil at room temperature.
How would boiling water at room temperature affect cooking time?
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Boiling water at room temperature would increase cooking time because the water would not be as hot as it would be at its normal boiling point.
Can you think of a situation where boiling water at room temperature would be useful?
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Boiling water at room temperature could be useful in medical procedures or laboratories where heat-sensitive substances need to be sterilized.
What would happen if you suddenly increased the atmospheric pressure on boiling water?
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If you suddenly increased the atmospheric pressure on boiling water, the boiling process would slow down or stop because the vapor pressure would no longer exceed the external pressure.
Could you boil water at room temperature using sunlight?
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Yes, using a solar collector or concentrating sunlight, you could heat water to the point of boiling at room temperature.
What safety precautions should be taken when experimenting with boiling water at room temperature?
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Safety precautions when experimenting with boiling water at room temperature include wearing protective eyewear and gloves to prevent any injuries from hot water or steam.
How does the boiling point of water change at extremely high altitudes, like on top of Mount Everest?
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At extremely high altitudes, such as on top of Mount Everest, the boiling point of water is significantly lower, making it harder to cook food or boil water.
Can you think of any other liquids that can boil at room temperature under specific conditions?
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Yes, other liquids such as liquid nitrogen or certain volatile chemicals can boil at room temperature under specific conditions.
What would happen if you tried to boil water in a paper cup without adjusting the pressure?
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If you tried to boil water in a paper cup without adjusting the pressure, the cup would likely catch fire because the boiling water would exceed the cup's temperature resistance.