Properties of a substance which can be measured or observed without altering the identity of the substance being measured are . A.) physical properties B.) chemical properties C.) reactive properties D.) phase properties

The correct answer is physical properties and/or phase properties.

Explanation:

Chemical properties can alter the substance (if you burn wood, it becomes ash and is no longer wood).

Reactive properties are also chemically changing the substance.

Phase properties are where the element can be in solid, liquid, or gas form so these could also be an answer.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .