Physical Properties of Ammonia by keypoint It is a colourless gas with choking smell. It is poisonous in large quantities. It turns damp red litmus blue, so it is an alkaline gas It is less dense than air. It is very soluble in water Others are Viewing: Chemical Properties of Ammonia Ammonia Test for Ammonia Uses of Ammonia Physical Properties of Hydrogen Physical Properties Of Oxygen Physical Properties Of NO2