Final answer:
The stirring of a powder into a liquid that causes bubbling, heat release, and solid formation is indicative of the creation of a new substance, confirming a chemical change has taken place.
Step-by-step explanation:
Based on the observations where stirring a powder into a liquid results in bubbling, the release of heat, and the formation of a solid, a new substance is formed during the procedure. The formation of a new substance indicates that a chemical reaction has occurred.
Some key observations that support this include the temperature change, which is the heat release, and the formation of bubbles, which are not due to boiling, but likely because a gas has been produced at the temperature of the original materials. Moreover, the emergence of a solid suggests the creation of a precipitate. All these signs point to a chemical change where the initial substances change into something entirely different with unique properties. This is unlike a new element, which cannot be formed through such a process, or a new source of energy, which refers to the potential or ability to do work and not a substance. And, it is not just a physical mixture since the individual components cannot be separated by physical means like filtering or distillation.