V = 10 l = 10 dm³ dla wody 1 dm³ ma masę 1 kg m₁ = 10 kg T₁ = 10⁰C cw₁ = 4200 J /kg * ⁰C m₂ = 1 kg T₂ = 200⁰C cw₂ = 460 J/kg * ⁰C Tk = ? korzystamy z zasady bilansu cieplnego:
woda pobiera energię Q₁, stal oddaje energięQ₂ Q₁ = Q₂ m₁ * cw₁ * ΔT₁ = m₂ * cw₂ * ΔT₂ 10 kg * 4200 J/kg * ⁰C * ( Tk - 10⁰C ) = 1 kg * 460 J/kg * ⁰C * (200⁰C - Tk) 42000 J/⁰C * (Tk - 10⁰C ) = 460 J/⁰C * (200⁰C - Tk) 42000 J/⁰C * Tk - 420000 J = 92000 J - 460 J/ ⁰C * Tk 42000 J/⁰C * Tk + 460 J/⁰C * Tk = 92000 J + 420000 J Tk ( 42000 J /⁰C + 460 J/⁰C ) = 512000 J Tk = 521000 J /42460 J/⁰C Tk ≈ 12,06⁰C ≈ 12⁰C