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

Answer 1

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

B. The reaction releases heat.

This is an exothermic reaction where the formation of hydrogen gas from the zinc and hydrochloric acid releases energy, resulting in an increase in temperature of the test tube.