with the process of boiling water a person has to face every day.Hydrogen oxide is almost the most popular substance in our lives, but all we know about its properties?What happens to the compound in an amount which is eighty percent is a part of the human body, at the time when scorching bubbles fill the cup, and you in anticipation of a pleasant tea prepare everything for the ceremony.
Remembering school physics course, we can easily give an explanation of how the ice turns into liquid, and appears as a pair.But the difference of boiling and evaporation to respond to a course not everyone can.But the answer lies on the surface.Its simplicity and even some deeper meaning forced once again to pay tribute to the rational nature.
evaporation and condensation of liquid is continuously and constantly.But when the temperature reaches a certain critical point, referred to in the literature as the boiling point of water, the process of acquiring a high intensity.During boiling the water molecules move into the state of vapor, not only from the surface but also throughout the volume of the liquid.Visually, we see how the vapor bubbles are formed inside the kettle and quickly upward.
For each substance this critical point has its own temperature at a certain pressure.Normal conditions at sea level is considered the pressure of 100 kPa, boiling point of water under these conditions reaches the classical figure of 100 ° C up to the Rising 4,000 meters we come to terms, when the pressure falls and its value is 60 kPa.The boiling point of water in the mountains lower than at its foot, and for the conditions specified in the example, it reaches about 85 ° C
Tourists going to the long journey to the mountains, left at the bottom of the usual pots and pans.Since they take a special "pressure cooker."Closed space provokes an increase in pressure due to excess vapor pressure, resulting in increased temperature of boiling water, and you can safely cook familiar foods.
Has impact on the physical properties of the substance of its purity.The presence of impurities leads to a change in temperature of boiling.When dissolved in a liquid volatile substance, the boiling point of water slides down, otherwise, water boils at a higher temperature.
There are many interesting and unusual properties of water, which we have not even imagined.Experiments with plain water boiled and lead to interesting results.So rather paradoxical sounds, but there is a recognized fact that hot water freezes faster than ordinary water.Also, boil water faster than previously succumbed to boil, not much, but it affects the boiling point (freezing) the presence in water of salt.
Each of the above facts can be verified in a normal kitchen equipped with gas stove and refrigerator.It is quite another to determine what is the boiling point of water in vacuum, empirically.Theoretically under vacuum water boils at room temperature.
But for this experiment will require very simple equipment.Zapasёmsya conventional disposable syringe and a piece of clay.Preparations for the conduct of experience will require to make a simple manipulation of the needle.Sharp, confident movement breaks off the steel part of it, stop up the hole with plasticine.Fill the syringe of water at a tenth of the volume, remove the air and dress prepared for a needle on his "regular place" machine for experiments with vacuum ready.If
sharply otdёrnut piston back, the water turns to steam to the intensity of a full boil, and it is in a room where the temperature is about 20 ° C. Feeding the piston forward, we can see how the pair turns into a liquid.
For example, the properties of water, we again we see how interesting and unusual can store the most ordinary natural phenomena.
