Question

A student performs the following experiment in his school laboratory.

List two observations to justify that in this experiment a chemical change has taken place.

Answer 1

In the experiment where zinc (Zn) granules react with sulfuric acid (H₂SO₄), two observations that justify a chemical change are:

1. Evolution of Gas: When zinc reacts with sulfuric acid, hydrogen gas (H₂) is released. This can be observed as bubbling or effervescence around the zinc granules. The production of a gas is a key indicator of a chemical change.

2. Heat Generation: The reaction between zinc and sulfuric acid is exothermic, meaning it releases heat. The student would notice a temperature increase in the reaction mixture, further indicating a chemical change is occurring.

These observations confirm that a chemical reaction has taken place as new products are formed (zinc sulfate and hydrogen gas).