Gases, Vapors and Solvents

gases

materials in gaseous state at normal temperature and pressure

vapor

portion of liquid chemical that is diffused or suspended in air (partially gaseous phase)

solvents

liquids in which something can be dissolved

solute

substance dissolved in solvent

chemistry standard temperature and pressure (STP)

0C (32F) and 1 atm (760 mm Hg)

IH normal temperature and pressure (NTP)

25C (77F) and 1 atm (760 mm Hg)

what is vapor pressure specified at

standard temperature and pressure (STP)

volatility

substance tendency to evaporate at normal temperatures

vapor pressure (VP)

tendency to evaporate

• greater the VP the easier it is to evaporate

• VP is temperature dependent

polarity

polar substance dissolves more readily in polar solvents (like dissolves like)

boiling point

temperature at which VP of a liquid equals the surrounding pressure → liquid changes to vapor

flash point (FP)

lowest temperature that enough vapor given off can propagate a flame with an ignition source

autoignition temperature

temperature at which combustion will automatically occur (spontaneous ignition)

lower explosion limit (LEL)

lowest concentration of gas or vapor that will burn in air

upper explosive limit (UEL)

highest concentration of a gas or vapor that will burn in air

what is the range between LEL and UEL

flammable range for a gas or vapor

what are critical exposure factors

1) mode of use

2) control in place

types of air pollutants

carbon monoxide, nitrogen oxides, sulfur oxides, ozone