1) a standard for measuring properties of gases, 2) A state of pressure equal to 1 atmosphere (760 mm Hg/101.3 kPa) and at 273 K (water's freezing point).
A set of engineering reference conditions for dealing with gases with temperature equal to 273.15?K and pressure equal to 101.325 pascal.
273 K or 0 °C and 101 kPa (101 x 103 Pa).
0° Celcius and 1 atmosphere.
the condition 0 °C and 1 atmosphere of pressure.
The reference conditions for gases chosen by convention to be 0 degrees Celsius and 1 unit of atmospheric pressure.
Also referred to as "standard operating conditions," it is a term referring to the temperature and pressure to which all values are referenced for comparison. STP is generally 760 mm Hg (1 atm), 25°C.
STP is the environmental combination of 0° C and 1 atmosphere, which is a practical and easily maintained lab condition.