The law of conservation of mass is that the types of elements remain unchanged before and after the reaction. Because ammonium bicarbonate contains four elements: nitrogen, hydrogen, carbon and oxygen, it may generate water, carbon dioxide and ammonia after decomposition.

[Design Experiment] (1) Ammonia dissolved in water to form ammonia water belongs to alkali, which can turn dry red litmus paper blue;

(2) Carbon dioxide can make the clarified limewater turbid, so the limewater becomes turbid when gas is introduced into the clarified limewater, which proves that the gas is carbon dioxide; According to the experimental phenomenon, it is known that ammonia, water and carbon dioxide are produced, so the guess is correct;

[Reflection and Expansion] (1) Carbon dioxide reacts with sodium hydroxide to produce sodium carbonate and water. If hydrochloric acid is added, hydrochloric acid reacts with sodium carbonate to generate sodium chloride, water and carbon dioxide, so bubbles are generated, indicating that there is sodium carbonate in the solution, indicating that the product of ammonium bicarbonate decomposition contains carbon dioxide;

(2) Ammonium bicarbonate fertilizer is easy to decompose when heated, and should be stored in a cool, dark and sealed place.

So the answer is: conservation of mass; [Design experiment] (1) blue; (2) become turbid; Correct; [Reflection and Expansion ]( 1)

Experimental Steps Experimental Phenomena Chemical Reaction Equation Take a small amount of the reacted solution in a test tube, and dropwise add dilute hydrochloric acid with bubbles to generate Na2CO3+2HCl═2NaCl+H2O+CO2↑(2), which is cool, dark and sealed.