Question

$0.93\text{watt-hour}$ of energy is supplied to a block of ice at $0^{\circ }\text{C}$, weighing $10\text{g}$. It is found that-
[Latent heat of fusion of ice, $L=80\text{cal/g}$]

• A. Block of ice melts completely.
• B. Block of ice does not melt.
• C. Block of ice melts partially.
• D. Data insufficient

Answer 1

The correct option is A Block of ice melts completely.

Given that,
Energy supplied to block of ice $\left(H\right)=0.93\text{watt-hour}$
Mass of ice $\left(m\right)=10\text{gm}$
Mechanical equivalent of heat, $J=4.18\text{J/cal}$
We know that,
$1\text{watt-hour}=3600\text{J}$
$\therefore$ Energy supplied $\left(H\right)=0.93\times 3600\text{J}=3348\text{J}....\left(1\right)$
We know that, heat required to just melt $m\text{gms}$ of ice at $0^{\circ }\text{C}$ is given by
$Q=m\times L$
Thus,
Heat required to just melt $10\text{gms}$ of ice
$Q=10\times 80\times 4.18=3344\text{J}......\left(2\right)$
From $\left(1\right)$ and $\left(2\right)$, since $H>Q$,
we can conclude that the block of ice will melt completely.
Thus, option (a) is the correct answer.