Boiling water is changing into steam at this stage specific heat of water is:
A. <1
B. $\infty $
C. 1
D. 0

Hint: Boiling of water is an isothermal process because the temperature of water remains constant after reaching a boiling point and steam is evolved from water.

Step by step answer: Let’s assume, ${t_1}$= initial temperature
${t_2}$= final temperature
And ${t_2}$= change in the temperature..
The exchange of heat into or out of a system occurs so gradually that heat balance is kept up.
Since there is no change in the temperature in this process, we can write:
${t_2} - {t_1} = \Delta t$=0………………………………………………………………………………… (I)
When water starts boiling, the heat is given by = $Q$
The SI unit of heat is Joule
Since we know the heat of the body depends on the mass of the body and change in the temperature we can write:
$Q\alpha m\Delta T$
Hence we can represent it as:
$Q = ms\Delta T$………………………………………………………………………………….. (II)
Where m= mass of the water
s = proportionality constant
And proportionality constant itself is called specific heat
$s = \dfrac{Q}{{m\Delta T}}$………………………………………………………………………………… (III)
$\Delta T = 0$,
Equation (III) becomes
$s = \dfrac{Q}{{m \times 0}}$
$s = \dfrac{Q}{0}$
$s = \infty $
Hence, when boiling water is changing into steam at this stage specific heat of water is = $s = \infty $
Or we can say when boiling water changes into steam the specific heat produced is not defined.

Therefore option (B) is the correct answer.

Note: Boiling of water is an isothermal process. The different substances have various specific heat capacity. The substance that has the more specific heat capacity changes its temperature gradually and the substances that have less specific heat capacity changes its temperature faster.