The correct option is (b) 2 only.
Explanation
Respiration is a metabolic process where glucose is broken down in the presence of oxygen to release energy. The primary byproducts of aerobic cellular respiration are carbon dioxide and water. These byproducts are expelled from the body through the respiratory system.
Statement-wise Analysis
- Statement 1 is Incorrect. The moisture observed on the mirror does not originate from the water vapour already present in the surrounding air. Instead, it originates from within the body as a metabolic byproduct that is expelled via the lungs.
- Statement 2 is Correct. Exhaled air contains a significant amount of water vapour and is generally warmer than the surrounding environment. When this warm, moisture-laden breath comes into contact with the cooler surface of a mirror, the water vapour loses heat energy and condenses into tiny liquid water droplets, creating a foggy appearance.
- Statement 3 is Incorrect. Respiration does not consume water; rather, it produces water. The chemical equation for aerobic respiration is:
Glucose + Oxygen → Carbon Dioxide + Water + Energy.
Since water is generated as a product of this reaction, the presence of moisture confirms the production, not consumption, of water.
Key Takeaway: Aerobic respiration is an exothermic process that produces carbon dioxide and water as byproducts. The condensation of exhaled breath on a cold surface physically demonstrates the release of water vapour from the body.