State one appropriate observation for the following:
When dilute hydrochloric acid is added to sodium carbonate crystals.

Explanation

When dilute hydrochloric acid is added to sodium carbonate crystals, the following observation can be made:

**Observation:**
Bubbles of carbon dioxide gas (CO2) are evolved, which can be observed as fizzing or effervescence.

**Step-by-step Explanation:**

1. **Identify the Reactants:**
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