Physical properties of air:
Air is the gas that surrounds us. We can't see it or taste it, but we are able to feel the movement of air when it is windy.
At 0 degrees Celsius and one standard atmosphere (1.013×10^5 Pa) air has a density of 1.293g/L . The state of a gas at 0 degrees Celsius and one standard atmosphere pressure is called the standard state, and air in the standard state can be regarded as an ideal gas, and its molar volume is 22.4L/mol.
The specific heat capacity of air is related to the temperature, and at a temperature of 250K, the constant-pressure specific heat capacity of air is cp=1.003kJ/(kg*K). The temperature is 250K, the constant pressure specific heat capacity of air cp=1.003kJ/(kg*K). 300K, the constant pressure specific heat capacity of air cp=1.005kJ/(kg*K)
The state of the air:
The air at room temperature is a colorless and odorless gas, liquid air is a kind of easy to flow of the light yellow liquid. Generally when the air is liquefied carbon dioxide has been removed, so the composition of liquid air is 20.95% oxygen, 78.12% nitrogen and 0.93% argon, other components of the content is very small, can be ignored.
Air as a mixture of gases, condensing at constant pressure when the temperature decreases continuously, such as in the standard atmosphere (101.3KPa), air at 81.7K (dew point) began to condense, the temperature is reduced to 78.9K (bubble point) when all the transition to saturated liquid. This is due to the high boiling point components (oxygen, argon) began to condense more, while the low-boiling point components (nitrogen) to the end of the process is more condensed.
Composition of air:
The Earth's normal air composition by volume fraction is: nitrogen accounted for 78.08%, oxygen accounted for 20.95%, argon accounted for 0.93%, carbon dioxide accounted for 0.03%, and trace amounts of inert gases such as helium, neon, krypton, xenon and so on. Ozone, nitrogen oxide, nitrogen dioxide
In ancient times, air was thought to be a simple substance, in 1669, Mayu had based on the candle burning experiment, deduced that the composition of air is complex. The German Stahl put forward a general chemical theory in about 1700, which was the "combustion theory". He believed that there is an invisible so-called pyroxene, exists in the combustible material. For example, candle combustion, combustion of ions to escape, the candle shrinks and collapses into ashes, he believed that combustion loss of ions phenomenon, that is: candles - ions = ashes. However, the theory of ipecac cannot explain some of the phenomena in the natural world changes, it has serious contradictions. The first is that no one has seen the existence of "iguana"; second metal combustion mass increase, then "iguana" must have a negative quality, which is incredible. 1774 French chemist Lavoisier put forward the oxidation of combustion, only to negate the iguana doctrine. It was only in 1774 that the French chemist Lavoisier proposed the oxidizing theory of combustion, which rejected the kinetics theory. Lavoisier in the lead, mercury and other metals in the combustion experiment, found that part of the metal into a colored powder, air in the bell jar volume reduced by 1/5 of the original volume, the remaining air can not support the combustion, the animals will be suffocated in which. He called the remaining 4/5 of the gas nitrogen (which in the original means not supporting life), and the composition of the air was determined to be nitrogen and oxygen only after he proved that the gas prepared by Priestley and Scherrer from the decomposition of mercuric oxide was oxygen.
The predominance of nitrogen and oxygen in the composition of air is the result of various changes in nature over a long period of time. Before the emergence of primitive green plants, the original atmosphere was dominated by carbon monoxide, carbon dioxide, methane and ammonia. After the emergence of green plants, the free oxygen released by plants during photosynthesis oxidized carbon monoxide into carbon dioxide, methane into water vapor and carbon dioxide, and ammonia into water vapor and nitrogen in the primitive atmosphere. Later, as the photosynthesis of plants continued, most of the carbon dioxide in the air was absorbed in the process of photosynthesis in plants, and made more and more oxygen in the air, and finally formed the modern air dominated by nitrogen and oxygen.
Air is a mixture. The constant components of air are nitrogen, oxygen, and rare gases, and these components so almost constant, mainly as a result of various changes in nature to compensate for each other. The variable components of air are carbon dioxide and water vapor. The variable composition of the air varies entirely from region to region. For example, in the vicinity of a factory, the air contains ammonia, acid vapor, etc., depending on the production project. In addition, the air contains very small amounts of hydrogen, ozone, oxides of nitrogen, methane, and other gases. Dust is a more or less suspended impurity in the air. Overall, the composition of air is generally relatively constant.
Layering of air:
Air wraps around the outside of the Earth and is thousands of kilometers thick. This thick layer of air is known as the atmosphere. The atmosphere is divided into several different layers, and these layers of air actually blend into each other. We live in the lowest layer (known as the troposphere). In the stratosphere, where the air is much thinner, there is a gas called "ozone" (a type of oxygen), which absorbs harmful ultraviolet rays from the sun. Above the stratosphere is the ionosphere, a layer of charged particles called ions. The ionosphere plays a very important role in reflecting radio waves around the world. If water vapor, carbon dioxide and various hydrocarbons are not taken into account, the average composition of the air from the ground to 100km altitude remains constant. Ozone content increases at 25km altitude. At higher altitudes, the composition of the air varies with altitude and is clearly related to the time of day and solar activity.
"Heavy" air:
Air is not weightless - a bucket of air weighs about as much as two pages of a book. The air in the atmosphere is always pressurizing us with a pressure called atmospheric pressure, and our bodies bear about one kilogram of weight per square centimeter. Because we also have air inside us, this pressure is equal inside and outside, so that the pressure of the atmosphere does not crush us.
The air on which life depends:
Because the Earth has a strong attraction, so that eighty percent of the air is concentrated in the range of an average of fifteen kilometers from the ground. This air layer has a great impact on human life and production activities. People usually say that the air pollution refers to this range of air pollution.
Air is a necessary condition for the survival of plants and animals on Earth, animal respiration, plant photosynthesis can not be separated from the air; the atmosphere can make the temperature of the Earth to maintain a relatively stable, if there is no atmosphere, the daytime temperature will be very high, and the night temperature will be very low; the atmosphere can absorb ultraviolet rays from the sun, to protect the living creatures of the Earth from harm; the atmosphere can prevent high-energy particles from space too much into the Earth, to stop the The atmosphere can prevent too many high-energy particles from space to enter the Earth, to prevent meteorites from hitting the Earth, because meteorites and the atmosphere friction can be both slowed down and burned; the formation of wind, clouds, rain, snow can not be separated from the atmosphere; the propagation of sound to use the air; parachutes, deceleration parachutes and airplanes are also the use of the force of the air; some machines have to use the compressed air to do their work.
Air quality:
If there is no air, our planet would be a barren desert, without a trace of life. Green plants synthesize nutrients using carbon dioxide from the air, as well as sunlight and water, and in the process, oxygen is released. Humans and other animals breathe the air to get oxygen, and animals also need oxygen to get energy from the food they consume.
The development of industry has emitted harmful substances into the air, polluting it and adding harmful components to it. When the harmful substances in the air reaches a certain concentration, it will seriously damage human health and the growth of crops, the destruction of certain substances, and will make people less visible, affecting traffic safety and so on. Therefore, it is necessary to vigorously prevent air pollution.
Harmful substances emitted into the air can be divided into the following categories: dust (such as charcoal particles, etc.), metal dust (such as iron, aluminum, etc.), wet fog (such as oil mist, acid mist, etc.), harmful gases (such as carbon monoxide, hydrogen sulfide, nitrogen oxides, etc.). From a worldwide perspective, the harmful gases with more emissions and greater harm are sulfur dioxide and carbon monoxide. Sulfur dioxide is produced in the combustion of coal and oil. Carbon monoxide is mainly emitted when cars are driven. From global estimates, the amount of carbon monoxide emitted exceeds the amount of sulfur dioxide emitted.
According to the unified regulations of the State Environmental Protection Administration, the air quality in China is divided into 5 levels. It is a series of complex air monitoring data, according to a certain method of processing, calculate its air pollution index is specifically how much, and then determine its air quality level.
Its specific standards are as follows: when the air pollution index reaches 0-50 for level 1; 51-100 for level 2; 101-200 for level 3; 201-300 for level 4; 300 or more for level 5. Level 3 is mildly polluted, level 4 is moderately polluted, and level 5 is heavily polluted.
Air humidity and quality
Humidification The process of increasing the moisture content of the air.
Humidity The degree of how much moisture is in the air per unit.
Negative ions There are many charged particles floating in the air, which we call "air ions", and there is a difference between positively and negatively charged air ions, and negatively charged air ions we call "negative ions".
Relative humidity is usually used to indicate the level of humidity, and is measured in %RH. It reflects the ability of air to approach a saturated state. The higher the humidity, the closer the air is to saturation. Conversely, the lower the humidity, the drier the air.
Ultrasonic atomization principle The use of ultrasonic transducer will be converted into mechanical energy characteristics, in the 1.7 million times / second high-frequency vibration, the water atomized into ≤ 5 μ m of ultra-fine particles, the formation of water mist.
Ultrasonic humidifier The water mist will be diffused into the air through the wind device to increase the humidity of the surrounding air equipment. It is currently the main product on the humidification market, with power consumption, low noise, humidification is obvious and produce negative oxygen ions and other characteristics.
Atomization humidification through the physical method of water into a fine mist sprayed into the humidified environment. Specific mechanical centrifugal humidification, water spray humidification, high pressure spray humidification, ultrasonic humidification.
Evaporative humidification The water is heated to produce steam, sprayed into the humidified environment. Divided into self-produced steam humidification and boiler or steam pipe network to provide dry steam humidification. One of the self-produced steam humidification, can be divided into electrode humidification, electric humidification, gas humidification, infrared humidification.
2, negative ions humidification and health common sense
In daily life, dry air is easy to make the elderly, young children and other weak body resistance to infection of the population; able to make the spread of epidemics (influenza, etc.); easy to produce static electricity, resulting in discomfort. Dry air is easy to make the skin muscle fiber deformation, fracture, the formation of irrecoverable wrinkles; because, the human skin is composed of muscle fibers, muscle fibers are composed of a large number of water-soluble collagen, drying will make the muscle fibers due to rapid water loss and contraction, the drier the environment, the faster the contraction of the tighter. Over time, long-term tension in the state of muscle fibers may be deformed fracture, the formation of irrecoverable wrinkles. This common sense, has been a lot of beauty ladies are familiar with, which is also the cosmetics market moisturizing products are highly favored reasons. But people ignore the point, in fact, really change the degree of dryness in the environment, increase indoor humidity, to keep the skin moist is the most fundamental, the most direct and the most economical beauty methods. Medical research has shown that in a dry environment, the resistance of the human respiratory system is reduced, easily triggered or aggravated respiratory diseases. Some research results show that when the air humidity is lower than 40% RH, nasal and lung respiratory mucosa dehydration, elasticity is reduced, mucus secretion is reduced, the cilia on the mucous membrane slowed down, dust, bacteria, etc. are easy to adhere to the mucous membrane on the early stimulation of the larynx triggered by coughing, but also prone to bronchitis, bronchial asthma, as well as other respiratory tract diseases. In the north of China, every winter heating season, people indoors feel extra dry. The optimal humidity for human beings is between 45%RH -- 65%RH, while the indoor humidity during the winter heating season is generally only 15-20%RH. That's why you tend to get hot and uncomfortable. One way to alleviate the discomfort caused by cold, dry noses and dehydration is to humidify. Indoors is where we spend most of our time. Dry air is actually an air quality issue for most people. Dry air contributes to the growth of bacteria, viruses and respiratory irritants that can cause far more damage to sensitive people than dry skin. Proper indoor humidity increases the body's resistance to indoor respiratory pollutants and irritants.
3, negative ions and air purification environment
a, ionized air
Ionized air is widely present in nature, because of its existence constitutes a new discipline ---- electrical Hou science. Negative ions are an important component of ionized air, has a very important role in human beings and living creatures, known as the air vitamins and growth factors.
The ionized air of nature is generated by lightning, ultraviolet light, cosmic ray irradiation and radiation of radioactive elements on the earth's crust, which ionize the molecules in the air, or due to waterfalls, the impact of the waves, so that the water droplets are split, free electrons, so that the air is charged, and produce ionized air. Artificially generate ionized air process more uneven electric field, corona discharge, in order to achieve the ionization of air molecules, positive corona ionization when the loss of electrons atoms or molecules, to become positively charged positive ions; negative corona ionization when the acquisition of electrons atoms or molecules, to become negatively charged negative ions. With ultrasonic atomization method, ultraviolet irradiation method, high-pressure water spray method, etc., can also produce negative ions.
Ionized air is colorless, odorless, tasteless, with the sense organs do not touch, susceptible to the influence of the external electric field and a variety of objects isolated or absorbed, in the ultrasonic or electric field, the role of the atom or molecule are light negative ions, in the air of the human living environment, light negative ions in the concentration of 1,000 per cubic centimeter or more appropriate.
Second, negative air ions and human health
Since 1931, a German doctor found that negative ions in the air, positive ions on the human body after more than half a century, has been for Europe, the United States, the Soviet Union, Japan and other countries are actively studying the subject. Through the positive and negative ions in the atmosphere monitoring, research, people have found that the atmosphere, air ions are dominated by atmospheric electric field strength, weakness and constitute one of the main factors in the environment to maintain the ecological balance, from the atmosphere of ions in the light, heavy ratio can be seen in the high and low levels of environmental pollution, such as light ions concentration is high, the degree of environmental pollution is relatively low, and vice versa, the degree of pollution is high, the impact on human health will be large, with the space of the Positive and negative ion concentration is different, different weight, dominated by biological physiological conditions are different, also have different responses to pathology, high concentration of light negative ions, can make people concentrate, mental stimulation, work efficiency, on the treatment of the respiratory system, the immune system, the nervous system and hematopoietic system function and other diseases have auxiliary therapeutic effect. In health care, daily inhalation of high concentration of light negative ion air, the human lung oxygen function can increase 20%, carbon dioxide discharge can increase 14.5%, half an hour a day "negative ion shower", the human spirit, mood, thinking, memory, etc., have certain enhancement and improvement.
Recent scientific development, environmental science is increasingly concerned about the scope of human activities from land to space, the depths of the Earth, as well as the depths of the ocean; these places, people want to enter a man-made environment, such as submarines, word Zuizhou spaceships, sealed air-conditioned indoor and other special environments to work in the public **** place of movie theaters, hotels, restaurants, crowded department stores or shopping malls, etc., are to properly increase the negative ions in the air. All to increase the concentration of negative ions in the air, in order to make people refreshed, clear-headed, emotionally stable, and effectively improve work efficiency.
Third, negative air ions and artificial environment
Through the positive and negative ions in the atmosphere, monitoring, research, people also found that in thunderstorms, waterfalls, fountains, seaside and other areas, the negative air ions concentration can be increased to 10,000 per cubic centimeter into dry. And in the city, busy traffic areas, industrial areas, densely populated places, the positive ion concentration increases, the negative ion concentration is only a few dozen per cubic centimeter. Ionized air has an ameliorating effect on environmental pollution. Negative ions formed in the corona discharge at the same time generate trace O 3, diffused in space, the polluted air has a purifying, sterilization effect. In addition, ionized air inhibits the growth of mold, eggs, vegetables, fruits and other freshness. Drinking water has a special role in sterilization, disinfection.
In order to improve people's living and working environment space, my company developed a variety of ultrasonic negative ion atomization equipment, through the atomization chip of 1.7MHZ high-frequency ultrasonic resonance, the water will be thrown away from the water surface, so that the water droplets decomposition and produce natural floating water mist, due to the ultrasonic vibration of the role of the water contains a large number of negative ions in the water mist. In densely populated communities, hotels, restaurants, public **** places, etc., the use of ultrasonic fogging equipment produced by my company, can be very good to improve environmental air quality. Such as can be equipped with artificial landscaping, bonsai gardening, fountains and pools, aquarium technology, decorative crafts, etc., can be brought as if in the waterfalls, forests in the beautiful environment. For the health of all of us, for all of us *** with the environment, let us *** with efforts to create a better living environment.
Fourth, it is reported that the high-voltage dynamic air disinfector using "high voltage, electrostatic, plasma" sterilization principle, the disinfection process: the high voltage into the three-level cellular electric field, resulting in plasma feed light, and then the circulating wind into the high-voltage electric field for carbonization (burned off). Positive and negative ions hit each other, the dust will be crushed to one hundred thousandth of the original carbonized volume, and then through the static network adsorption and activated carbon filtration, so that the cleanliness of indoor air up to ten thousand levels below. The whole process of disinfection and dust removal is carried out inside the equipment, the sterilized air is re-discharged to the room, and the air containing bacteria and dust enters into the sterilizer to be processed again; such a cycle can make the air in the workshop always keep in a clean state. High-voltage air dynamic sterilizer is an advanced disinfection equipment, used to be mainly used for air hygiene quality requirements of the medical industry is very high operating room; in recent years, this equipment is also gradually used in some large-scale food enterprises in the processing and packaging process. It is reported that the domestic has Suzhou Kang Xi Medical Purification Equipment Co., Ltd. and other enterprises to develop and produce multi-functional high-voltage air sterilizer.
[edit]Lavoisier determination of air composition
More than 200 years ago, the French scientist Lavoisier quantitative test method to determine the air composition.
He put a small amount of mercury in a closed container and heated it for 12 days, and found that some of the mercury turned into a reddish powder, and at the same time, the volume of the air was reduced by about 1/5. By studying the remaining gas, he found that it could not supply respiration and did not aid in combustion, and he mistakenly believed that it was all nitrogen.
Lavoisier again collected the red powder produced by heating, and put it in another smaller vessel and reheated it, obtaining mercury and oxygen, and the volume of oxygen exactly equal to the volume of air reduced in the closed vessel. He introduced the oxygen obtained into the previous container, the resulting gas and air are identical in nature.
Through the experiment, Lavoisier concluded that the air is composed of oxygen and nitrogen, and oxygen accounts for 1/5 of it.
Before the 19th century, it was thought that there was only nitrogen and oxygen in the air. Later, some rare gases were discovered. At present, people can accurately measure the composition of air.
[edit]Composition of air
Nitrogen: 78%
Oxygen: 21%
Rare gases: 0.94%
Carbon dioxide: 0.03%
Other: 0.03%
Air is a mixture of many gases. Its constant components are oxygen and other rare gases, and its variable components are carbon dioxide and water vapor, the amount of which varies slightly within a small limit depending on the location and temperature of the earth. As for the variable components in the air, they vary according to different regions, for example, sulfur dioxide is contained in places close to metallurgical factories, and chlorine is contained in places close to chlor-alkali factories, etc. In addition, there are traces of hydrogen and other rare gases in the air. In addition, there are traces of hydrogen, ozone, nitrogen oxide, methane and more or less dust in the air.
Experiments have shown that the percentage content of constant components in the air is almost constant up to an altitude of 100km above the ground. In terms of volume content, oxygen accounts for about 20.95%, nitrogen accounts for about 78.09%, and argon accounts for about 0.932%,
Generally speaking, the composition of air is relatively fixed. This is very important for the survival of human beings and other animals and plants. However, with the development of modern industry, harmful gases and soot emitted into the air, changing the composition of the air, resulting in pollution of the air. Polluted air can seriously harm human health, affect crop growth, and cause damage to natural resources and buildings.
Harmful substances emitted into the air can be broadly categorized into dust and gas. Worldwide, the gaseous pollutants emitted into the air are sulfur dioxide, carbon monoxide, nitrogen dioxide, etc. These gases come mainly from fossil fuels (coal). These gases come mainly from the combustion of fossil fuels (coal and oil) and factory exhaust.
Explanations of "air" in the Chinese-English dictionary (Source: Baidu Dictionary):
1. air
2. (in abstract sense) atmosphere