Question

Which is the most important question for deciding if a chemical reaction has occurred?

Answer 1

Answer:

all these are physical properties except release of heat so it's probably heat energy given off

Answer 2

Answer:Was any heat energy given off?

Explanation:

A chemical reaction may exothermic (heat is given off) or endothermic (heat is absorbed). Size, density or texture of the substance are strictly physical properties which cannot confirm that a chemical reaction has transpired in the sample. The evolution of heat ultimately confirms that a chemical process has taken place.