Answer: Bubbles formed would be evidence that a chemical reaction took place when the solutions were combined.
Explanation:
As it is given that both [tex]Na_{2}CO_{3}[/tex] and HCl chemically combine together leading to the formation of NaCl, water and carbon dioxide gas. As the gas is forming and its formation will also form bubbles into the solution.
This formation of bubbles actually indicate that a chemical reaction has taken place. As molecules of a gas are held by Vander waal forces so, this gas will readily escape into the atmosphere.
Thus, we can conclude that bubbles formed would be evidence that a chemical reaction took place when the solutions were combined.