Does it take more, less, or the same amount of heat to melt 1.0 kg of ice at 0°C, or to bring 1.0 kg of liquid water at 0°C to the boiling point? Assume that, for water, 4186 J/(kg ·°C) and 3.35×105 J/kg.

Respuesta :

Answer : It takes less amount of heat to metal 1.0 Kg of ice.

Solution :

The process involved in this problem are :

[tex](1):H_2O(s)(0^oC)\rightarrow H_2O(l)(0^oC)\\\\(2):H_2O(l)(0^oC)\rightarrow H_2O(l)(100^oC)[/tex]

Now we have to calculate the amount of heat released or absorbed in both processes.

For process 1 :

[tex]Q_1=m\times \Delta H_{fusion}[/tex]

where,

[tex]Q_1[/tex] = amount of heat absorbed = ?

m = mass of water or ice = 1.0 Kg

[tex]\Delta H_{fusion}[/tex] = enthalpy change for fusion = [tex]3.35\times 10^5J/Kg[/tex]

Now put all the given values in [tex]Q_1[/tex], we get:

[tex]Q_1=1.0Kg\times 3.35\times 10^5J/Kg=3.35\times 10^5J[/tex]

For process 2 :

[tex]Q_2=m\times c_{p,l}\times (T_{final}-T_{initial})[/tex]

where,

[tex]Q_2[/tex] = amount of heat absorbed = ?

m = mass of water = 1.0 Kg

[tex]c_{p,l}[/tex] = specific heat of liquid water = [tex]4186J/Kg^oC[/tex]

[tex]T_1[/tex] = initial temperature = [tex]0^oC[/tex]

[tex]T_2[/tex] = final temperature = [tex]100^oC[/tex]

Now put all the given values in [tex]Q_2[/tex], we get:

[tex]Q_2=1.0Kg\times 4186J/Kg^oC\times (100-0)^oC[/tex]

[tex]Q_2=4.186\times 10^5J[/tex]

From this we conclude that, [tex]Q_1<Q_2[/tex] that means it takes less amount of heat to metal 1.0 Kg of ice.

Hence, the it takes less amount of heat to metal 1.0 Kg of ice.