Question

How long will it take a 50W heater to melt 100g of ice at 0 celsius degree

Answer 1

$Q=Lm$

Q is the amount of heat needed to melt the ice 

L is the latent heat of melt for ice, that is

m  is the mass of ice that is to melt

$m=100g=0.1kg$

$Q=3.34.10^{5}\times0.1= 33.4kJ$

We know that $Power=\frac {E}{P}$

Therefore$t=\frac{E}{p}= \frac{33.4kJ}{50}$

$t=668 seconds$