Odpowiedź:
Energia pobrana : Q₁ + Q₂
m₁ = 50 g = 0,05 kg
t₁ = -5 C
t₂ = 0 C
t₃ = 15 C
cl = 2100 /kg * C
ct = 334000 J/kg
Energia oddana: Q₃
m₂ = ?
t₃ = 40 C
cw = 4200 J/kg * C
t = 15 C
Q₁ + Q₂ + Q₃= Q₃
m₁ * cl * (t₂ - t₁ ) + m₁ * ct + m₁ * cw* (t₃ - t₂) = m₂ * cw * (t₃ - t )
0,05 kg *2100 J/kg * C * [ 0C -(-5 C)] + 0,05 kg *334000 J/kg + 0,05 kg * 4200 J/kg * C * 15 C = m₂ * 4200 J/kg * C * (40 C - 15 C)
525 J + 16700 J + 3150 J = m₂ * 105000 J/kg
20375 J = m₂ * 105000 J/kg
m₂ = 20375 J / 105000 J/kg
m₂ = 0,19 kg
