In a science demonstration, a teacher mixed zinc (Zn) with hydrogen chloride (HCl) in a flask and quickly attached a balloon over the mouth of the flask. Bubbles formed in the solution and the balloon inflated. What most likely occurred during this demonstration? The Zn and HCl both retained their identity. Either Zn or HCl, but not both, retained its identity. Evaporation of one of the substances occurred. One or more new substances formed.