What is the ordinary atmospheric pressure?

Standard atmospheric pressure is the pressure at sea level under standard atmospheric conditions, which was put forward by physicist Torricelli at 16438+0.325 kpa, and its value is 10 1.325kPa, which is the unit of pressure and is recorded as atm.

In chemistry, the standard temperature and pressure (STP) was once defined as 0 C (273.15k) and101.325kpa (1ATM), but starting from 1982, IUPAC will 1 standard atmospheric pressure = 760mmhg = 76cmhg =1.01325x105pa =10.339m water column.

Extended data:

With the development of science and technology, the standard atmospheric pressure has changed several times. At first, the atmospheric pressure at sea level of 0℃ and latitude of 45 on a clear day was defined as the standard atmospheric pressure, which was about 760mm Hg high. Later, it was found that the air pressure value under this condition was unstable and changed under the influence of wind, temperature and other conditions.

Therefore, the height of 760 mm Hg is defined as the standard atmospheric pressure value. However, it was later found that the pressure value of 760mm Hg was also unstable, and the density of mercury changed under the influence of temperature. The value of g also varies with latitude. In order to ensure that the standard atmospheric pressure is constant, 1954, the resolution of the 10th International Metrology Conference called the standard atmospheric pressure101.325kpa..

The earth is surrounded by thick air, which is called the atmosphere. Air can flow freely like water and is also influenced by gravity. So there is pressure in all directions in the air, and this pressure is called atmospheric pressure. 1643, an Italian scientist Torricelli filled an 80cm-long thin glass tube with mercury and inverted it in a water tank filled with mercury. He found that the mercury in the glass tube dropped by about 4 cm, and then stopped falling.

There is no air in this 4 cm space, it is a vacuum. Torricelli deduced from this that the pressure of the atmosphere is equal to the length of the mercury column. According to the pressure formula, scientists accurately calculated that the atmospheric pressure in the standard state was1.01×105pa. In order to prove the existence of atmospheric pressure and vacuum, Gehrig made a famous experiment in Madburg, Germany in 1654, which made people have a profound understanding of atmospheric pressure.

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