Identify Evidence of Chemical Reactions Practice Test

A student drops a small piece of magnesium ribbon into a cup of hydrochloric acid. During the next minute, the student sees rapid bubbling, the metal strip gets smaller until it disappears, and the cup feels noticeably warm. Which observation is evidence that a chemical reaction occurred?

A student mixes two clear solutions in a cup. The mixture begins to fizz, and a sharp new odor appears that was not present in either solution beforehand. No boiling is occurring. Which observations are evidence of a chemical reaction? (Select the best answer.)