a volatile substance
a substance that changes readily from solid or liquid to a vapor
"it was heated to evaporate the volatiles"
tending to vary often or widely
marked by erratic changeableness in affections or attachments
"a flirt's volatile affections"
liable to lead to sudden change or violence
"an explosive issue"
"a volatile situation with troops and rioters eager for a confrontation"
evaporating readily at normal temperatures and pressures