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

Answer 1

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

A. The reaction releases heat.

This is because the reaction between zinc and hydrochloric acid is exothermic, meaning it releases heat to the surroundings, causing the test tube to feel hot.