When baking soda is heated, it undergoes a chemical change. Write the balanced equation for this reaction. What product causes bread to become soft and spongy during baking?
Generated by claude-sonnet-4-6 · 2026-06-17 12:37 · grounding rag
Model Answer
When baking soda (sodium hydrogen carbonate) is heated, it decomposes as follows:
$$2\text{NaHCO}_3(s) \xrightarrow{\Delta} \text{Na}_2\text{CO}_3(s) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$$
The carbon dioxide (CO₂) gas released during this reaction gets trapped in the dough, causing it to rise and become soft and spongy during baking.
Explanation
- The balanced equation must show 2 moles of NaHCO₃ on the left; examiners deduct marks for unbalanced equations.
- Clearly name CO₂ as the product responsible for the spongy texture — this is the direct answer to the second part and earns a separate mark.
- The three marks split roughly as: 1 mark for correct reactant/products, 1 mark for balancing, 1 mark for identifying CO₂ as the cause of soft/spongy bread.