reaction 1: magnesium plus hydrochloric acid.

Question

a small piece of a silvery metal (magnesium) and a container of clear hydrochloric acid. Small bubbles are seen accumlating on the metal strip.
was this a chemical reaction or a physical reaction? How do you know?

Answer 1

The reaction you are observing between magnesium and hydrochloric acid is a chemical reaction. You can identify it as such for a few reasons:

1. Formation of Bubbles: The small bubbles forming on the magnesium strip indicate the production of a gas. In this case, hydrogen gas (H₂) is produced as a result of the reaction between magnesium (Mg) and hydrochloric acid (HCl). The generation of a gas is a common sign of a chemical reaction.

2. Change in Chemical Composition: In a chemical reaction, the original substances are transformed into new substances with different chemical properties. Here, magnesium reacts with hydrochloric acid to form magnesium chloride (MgCl₂) and hydrogen gas (H₂). The original reactants (magnesium metal and hydrochloric acid) are changed into these new products, which is indicative of a chemical change.

3. Energy Changes: Chemical reactions often involve changes in energy, either in the form of heat or light. Although you didn't specify whether there was a noticeable temperature change, many reactions involving acids do release or absorb heat.

In summary, the bubbling and the transformation of materials indicate a chemical reaction taking place.