Question

The heat needed to turn 1 kg of liquid into gas at its boiling point is known as:
A) Latent heat
B) Specific latent heat of vaporization
C) Specific latent heat of substance
D) Fermentation

Answer 1

Hint:At boiling/condensation temperature of melting/freezing temperature each substance requires some amount of heat energy to absorb/release. This extra amount of heat that doesn’t change the temperature but changes the state is known as latent heat. For a specific type of change of state it’s called specific latent heat for that change of state.

Explanation:
(a) Latent heat: Latent heat is known as the heat released or absorbed by any substance or any thermodynamic system for its conversion from one state to another. This is a constant temperature process as that absorbed or released heat doesn't change the temperature of the substance but only changes its state either from solid to liquid or from liquid to gas and vice versa. For boiling and melting, heat is absorbed while for freezing and condensation heat is released.

(b) Specific latent heat of vaporization: Specific latent heat of vaporization is the amount of heat absorbed by some liquid at its boiling temperature to vaporize i.e. to change its state to liquid to vapor or gas. This absorbed heat doesn’t raise the temperature but it changes the liquid into vapor/gas. Hence, the heat needed to turn 1 kg of liquid into gas must be this type of heat.

(c) Specific latent heat of substance: This option is completely a vague option. As any substance can have three states so there can be two types of change of state. Hence, two types of latent heat exists for any substance. So, there is no concept called specific heat of substance.

(d) Fermentation: Fermentation is one kind of metabolic process that produces some chemical changes within the organic substance, through application of some enzymes. It is a process that absorbs energy from carbohydrates in absence of oxygen.

Correct answer:
The heat needed to turn 1 kg of liquid into gas at its boiling point is known as (b) Specific latent heat of vaporization.

Note: Here, if you answer the required heat as latent heat then technically it shouldn’t be a wrong answer as this is indeed one type of latent heat. But here a more specific answer i.e. specific latent heat of vaporization is given as an option so your answer must be this option not the previous one.