Aurelia dropped a piece of metal into a beaker, and then she added acid to it. She saw colorless bubbles rising from the metal. The metal began to turn black. What type of change did Aurelia see?

Chemical change

Explanation:

From all indicators, Aurelia is seeing a chemical change occurring in the reaction here.

A chemical change is a change in which new substances are produced. For every chemical change:

We start off and end with:

         Metal   +     Acid →     Black metal     +    rising gaseous bubbles

Clearly, it is shown that new products are formed and this reaction is impossible to reverse in order to get the reactants back.

This is a typical chemical change.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

i think it's letter a.