Question

An electric heater 1000W is used to heat 0.2kg of ice. Initially at -10°C to until all the mass changes to steam at 100°C.
Specific heat capacity of ice = 2.1 x 10³ JKg^-1K^-1
Latent heat of fusion of ice = 3.34 x 10⁵ JKg^-1
Specific heat capacity of water = 4.2 x 10³JKg^-1K^-1
Latent heat of vaporization of steam = 2.26 X 10⁶Kg^-1
Calculate:

1. The amount of heat required to raise the temperature of ice from -10°C to ice at 0°C.   
2. The amount of heat required to convert ice into water at 0°C. 
3. The amount of heat required to raise the temperature of water at 0°C to water at 100°C.     
4. The amount of heat required to change water to steam at 100°C.     
5. The minimum time required in minutes for activity in (i) to (iv) to take place 

Answer 1

1. M_ice x C_ice x θ
   =0.2kg x 2.1 x 10³ JKg^-1K^-1 x 10K
   =4.2 x 10³J
   =4200J
2. M_wL_f
   =0.2Kg x 3.34 x 10⁵JKg^-1
   =6.68 x 10⁴J 
   =66,800J
3. M_wC₁₀ x θ
   =0.2 x 4.2 x 10⁵JKg^-1K^-1 100K
   =8.4 x 10⁴J
   =84,000J
4. ML_v
   =0.2Kg x 2.26 x 10⁶JKg^-1K^-1
   =4.52 x 10⁵J 
   =452,000J
5. Total heat=4.2 x 10⁵J +6.68 x 10⁴J + 8.4 x 10J +4.52 x 10⁵J
                 = 6.07x 10⁵J
   t=Total heat = 6.07x 10⁵J = 607s
         Power           1000w
   In minutes =10 minutes 7seconds
                   =10.117 minutes