When a piece of zinc metal is carefully placed in a beaker of strong acid, bubbles form on the surface of the metal and begin to rise to the surface. The bubbles most likely indicate that
A.
a new substance is being produced.
B.
the zinc metal is melting.
C.
the acid solution is boiling.
D.
a physical change is occurring.

A.  a new substance is being produced.

Explanation:

The bubbles most likely indicates that a new substance is being produced by this reaction. In essence, we describe this sort of change as chemical change.

In a chemical change, new substances are usually produced. They are accompanied by the evolution or absorption of energy.

The reaction of Zinc with a strong acid to produce bubbles on the surface of the metal indicates a chemical change and the formation of a new kind of substance.

Take for example, let zinc reacts with hydrocholoric acid, HCl;

   Zn         +      2HCl      →    ZnCl₂     +     H₂

Since Zn is higher than Hydrogen in the activity series, it will displace it from HCl and liberate hydrogen gas as a product. This will cause the bubbles observed in the reaction.

This is a chemical change and new products have been formed.

B and D are wrong because they are both physical changes.

C is wrong because no information about such is provided by the problem statement.

So, when a piece of zinc metal combines with a strong acid, a new kind of substance is produced.

- decrease the number of plants and animals living in the water.