In physical science lab, kim and dawn added small pieces of magnesium to hydrochloric acid. they noticed that bubbles formed, the test tube got hot, and the magnesium disappeared. what is a sign that a chemical reaction has taken place in this experiment? question options: temperature decreased gas is produced magnesium appeared odor

The physical signs of a chemical reaction were there with the mixture of Mg and HCl. First the bubbles probably indicated that a gas was being given off, most likely hydrogen gas, then when the test tube got hot that indicates an exothermic reaction (chemical reactions can be either exothermic ie creating heat or endothermic using up heat) and the disappearance of the magnesium shows that it combined with the HCl probably to form Magnesium chloride.