Question

How much heat is needed to change 5g of ice at 0 degrees C to water at 50 degrees C

Answer 1

Solution.

$m=5g=5\sdot10^{-3}kg;$

$t_1=0^oC;$

$t_2=50^oC;$

$\lambda=332\sdot10^3J/kg;$

$с=4200J/kg^oC;$

Heat is needed to melt the ice:

$Q_1=\lambda m;$

$Q_1=332\sdot10^3J/kg\sdot5\sdot10^{-3}kg=1660J;$

Heat is needed to heat ice water:

$Q_2=cm\Delta t;$

$Q_2=4200J/(kg^oC)\sdot5\sdot10^{-3}kg\sdot50^oC=1050J;$

The whole amount of heat:

$Q=Q_2+Q_2;$

$Q=1660J+1050J=2710J;$

Answer: $Q=2710J.$