You are asked to design an investigative procedure that distinguishes clearly between…
CHEMISTRY · Multi-part · CBSE · Chemistry · Is Matter Around Us Pure? · Is Matter Around Us Pure?
Problem
You are asked to design an investigative procedure that distinguishes clearly between physical and chemical change using two substances provided by your teacher:
• Solid ammonium nitrate, NH4NO3(s)
• Aqueous hydrochloric acid, HCl(aq), to be reacted with solid sodium bicarbonate, NaHCO3(s)
The goal is to collect multiple, independent forms of macroscopic evidence and to evaluate the relative strength of each type of evidence.
(a) Outline a step-by-step experimental procedure that uses BOTH systems—(i) dissolving ammonium nitrate in water and (ii) reacting hydrochloric acid with sodium bicarbonate—to generate observable data relevant to identifying chemical change.
(b) For each system, predict TWO distinct macroscopic observations you expect to measure or see if a chemical change occurs. Include at least one quantitative observation for each system.
(c) Propose a method for ranking the strength of the different observations you listed in part (b) as evidence for chemical change. State clear criteria for the ranking and apply them to produce a justified ordering from strongest to weakest evidence.
(d) Explain how your procedure controls variables so that observed differences between the two systems can be confidently attributed to chemical versus physical change rather than experimental error.