Atm in chemistry refers to atmospheric pressure. It is described as the pressure imposed by the weight of the atmosphere, which has a mean value of 101,325 pascals at sea level (roughly 14.6959 pounds per square inch).
ATM stands for standard atmosphere, a non-SI, non-metric, yet extremely practical measure of pressure.
1 atm corresponds to the atmospheric pressure at sea level and 0 degrees Celsius. Currently, it is specified as exactly 101,325 Pa (the pascal is the SI unit of pressure).
A standard atmosphere is a fundamental unit because it intuitively communicates pressure. 0.5 atm is half the current air pressure, whereas 2 atm is double the current air pressure.
In addition, 1 atm helps determine Standard Pressure and Temperature (STP). Although IUPAC specifies the pressure in STP as 100 kPa (about 1 percent less than 1 atm), some committees continue to use 1 atm.
When accurate air pressure is unimportant, the unit atm is utilized. For instance, I may mention that I heated my sample in dry air at 1 atm. In this instance, I am referring to the fact that I did not test the air pressure but imagined it to be around 1 atmosphere (atm).
When communicating with the general public or in scientific domains where the reference to the actual atmosphere is essential, atmospheres may also be employed.
The standard atmosphere is not Si, not metric, and somewhat coarse. Additionally, the unit “total atmospheres” (ATA) is used when dealing with the pressure of various fluids.
Underwater, for instance, is both water pressure and air pressure; a scientist who rejects the SI system may choose to express water pressure in ATA to account for the above air pressure.
- Displays pressure in its intuitive terms
- A simple comparison to the real atmosphere
- Quickly communicates to the broad public
- It is not SI nor metric
- Somewhat coarse
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