When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it?
Answer & explanation
Correct answer: option 2
The correct answer is option 2. Chemical change.
When baking soda is mixed with lemon juice, and bubbles are formed with the evolution of a gas, it is indicative of a chemical change. Therefore, the correct answer is Chemical change
1. Chemical Change:
In this reaction, baking soda (sodium hydrogen carbonate, NaHCO₃) reacts with lemon juice (citric acid) to produce carbon dioxide gas (CO₂), water (H₂O), and a soluble salt (sodium citrate):
\[ \text{NaHCO}_3 + \text{H}^+(\text{from lemon juice}) \rightarrow \text{CO}_2 + \text{H}_2\text{O} + \text{Na}^+(\text{from sodium citrate}) \]
2. Gas Evolution:
The formation of bubbles and the evolution of a gas (carbon dioxide) are characteristic signs of a chemical change. The reaction involves the breaking and forming of chemical bonds, resulting in the conversion of reactants into new substances.
3. Physical Change vs. Chemical Change:
In a physical change, the substance undergoes a change in its physical state or appearance without a change in its chemical composition. In a chemical change, the substance undergoes a transformation at the molecular level, resulting in the formation of new substances with different chemical properties.
In the case of baking soda and lemon juice, the reaction involves a chemical change as new substances are formed (carbon dioxide, water, and salt), and this is accompanied by the release of gas in the form of bubbles.