WBCS.LIVE practice question

The density of water at 20° C is 998 kmg-3 and that at 40°C is 992 kmg-3. The coefficient of the cubical expansion of water is:

Solve this multiple-choice question and check the correct answer with its explanation below.

Answer options

  1. 2*10-4° c-1
  2. 6*10-4° c-1
  3. 3.00*10-4° c-1
  4. 4*104° c-1

Correct answer and explanation

Correct answer: 3.00*10-4° c-1

Explanation: The coefficient of cubical expansion of water between 20°C and 40°C is 3 × 10⁻⁴ °C⁻¹. 📚 Other Information: ▪️ Formula: β = ΔV / (V × ΔT). ▪️ Density at 20°C = 998 kg/m³, at 40°C = 992 kg/m³. ▪️ Δρ/ρ = βΔT (approximation for liquids). ▪️ Here β = (998–992) / (998 × 20) ≈ 3 × 10⁻⁴ °C⁻¹. ▪️ Expansion of water is anomalous between 0–4°C. ▪️ Important in lakes freezing phenomenon. ▪️ Water density maximum at 4°C. ▪️ Practical uses in thermodynamics and civil engineering.