Question

How much heat energy is required to change 2 kg of ice at 0c into water at 20c? (specific latent heat of fusion of water = 3,34,000j/kg, specific heat capacity of water = 4200jkg-1k-1).

Answer 1

$\bold{Given}$

$\boxed{Ice \: at \: 0c \longrightarrow Water \: at \: 20c}$

But in actual it changes like,

$\boxed{Ice \: at \: 0c \longrightarrow Water \: at \: 0c\longrightarrow Water \: at \: 20c}$

So,

▶In change of ice to water the state changes so, it will be taken as

$\boxed{mL}$

where m is mass and L is specific latent heat of fusion of water.

▶In change of water at 0 c to water at 20 c, there ia just increase in temperature so it will be taken as,

$\boxed{mc\Delta t}$

where m is mass, c is specific heat capacity of water and t is change in temperature.

So,

$\boxed{Ice \: at 0c \xrightarrow{mL} Water \: at \: 0c\xrightarrow{mc\Delta t} Water \: at \: 20c}$

◼Heat gained by ice = mL

= 2 × 334000

=6628000 J

◼Heat energy gained by water =mcΔt

=2 × 4200 × (20-0)

= 2 × 4200 × 20

=168000 g

Total heat energy taken= heat energy taken by ice + heat energy taken by water.

= 6628000 + 168000

=6796000 J