気体 is read as きたい (kitai) and means gas.
きたい
kitai
きたいはんのうのほうそく
law of combining volumes
きみ
sensation
かたぎ
disposition
きぶん
feeling
きもち
preparedness
きりょく
willpower
きらく
easygoing
きごころ
temper
きひん
aroma
きどう
respiratory tract
きふう
character
きやすい
relaxed