Ms. Pitt set up a classroom demonstration to show what happens when a sample of zinc metal is add a. ed to a flask containing hydrochloric acid (HCl). The diagram shows what the students in the classroom observed during the demonstration. The students made two other observations: The flask felt warmer after adding the sample. The sample became smaller over time. Which of the following is NOT an evidence of a chemical reaction in this example. A. Gas collected in the balloon
B. Temperature of sample is increased
c. Volume of HCl remains the same
D. Size of the zinc has become smaller