(dissolving or reacting) . All gases are less dense than liquid water and will displace the water downwards. No good for soluble gases like ammonia, hydrogen chloride, nitrogen dioxide or sulphur dioxide. You can collect in inverted gas jar if bigger sample required.You have to watch for 'sucking back' effects. Answer   Hydrogen can be collected by the downward displacement of water because of two reasons: it is less dense than water, and so rises to the surface, and it â¦ is not very soluble in water, and so nearly all the gas can be collected because very little is dissolved in the water.
preserve - a domain that seems to be specially reserved for someone; medicine is no longer a male preserve. 1  arena, domain, sphere, orbit, area, field - a particular environment or walk of life; his social sphere is limited; it was a closed area of employment; he's out of my orbit.
Food preservation refers to any one of a number of techniques used to prevent food from spoiling. All foods begin to spoil as soon as they are harvested or slaughtered.