Glossary of Chemistry Terms - U

U

• UN number - a four digit code used to note hazardous and flammable substances
• uncertainty - a characteristic that any measurement that involves estimation of any amount cannot be exactly reproducible
• Uncertainty principle - knowing the location of a particle makes the momentum uncertain, while knowing the momentum of a particle makes the location uncertain
• unit cell - the smallest repeating unit of a lattice
• unit factor - statements used in converting between units
• universal or ideal gas constant - proportionality constant in the ideal gas law (0.08206 L·atm/(K·mol))