Answer:
[tex]\boxed {\boxed {\sf C. \ Chemical, \ because \ a \ new \ gas \ formed}}[/tex]
Explanation:
Remember that a physical change only changes the appearance, while a chemical change creates completely new substances. Also, note that there are 5 main signs of a chemical change:
- Color change
- Temperature change
- Odor/smell production
- Bubbles/gas form
- Precipitate/new solid forms
In this experiment, acid was added to a piece of metal. Bubbles formed and the metal turned black. Therefore, 2 signs of a chemical change occurred. The metal changed colors and a gas was formed, signified by the bubbles. So, the best answer choice is C: A chemical change because a new gas was formed.
