Final answer:
The combination of sodium carbonate and hydrochloric acid results in a chemical change, forming aqueous sodium chloride, carbon dioxide gas, and water.
Step-by-step explanation:
When sodium carbonate and hydrochloric acid are combined, it is considered a chemical change because new substances are formed. This is evident as gas bubbles and a white residue are observed. The chemical reaction can be represented by the balanced equation: Na2CO3 (aq) + 2HCl(aq) → 2 NaCl (aq) + CO2 (g) + H2O (l). The formation of gas bubbles indicates the production of carbon dioxide, and the white residue is likely aqueous sodium chloride.
The formation of gas bubbles and the white residue demonstrate that a double-replacement reaction has occurred. In this type of reaction, the anions and cations of reactants swap to form new products, which, in this case, includes carbon dioxide gas that escapes into the air and water, alongside sodium chloride in solution, which appears as residue when the solution is dried.