When a strip of zinc metal is added to a test tube of hydrochloric acid, the liquid forms bubbles, and the test tube feels hot. The bubbles are a result of the formation of hydrogen gas. What does the hot test tube indicate?

Question

A.
A chemical change has been reversed.
B.
The reaction absorbs heat.
C.
The reaction releases heat.
D.
Hydrogen gas absorbs heat.

Answer 1

The hot test tube indicates that the reaction releases heat. Therefore, the correct answer is:

C. The reaction releases heat.

This is an exothermic reaction, where the formation of hydrogen gas from the reaction of zinc and hydrochloric acid releases heat, resulting in the test tube feeling hot.