Change of state refers to the transformation of a substance from one physical state to another, such as solid, liquid, or gas, by the absorption or release of heat.
Latent heat is the amount of heat absorbed or released by a substance during a change of state without any change in temperature.
The heat required to convert 1 kg of a solid into liquid at its melting point without change in temperature.
The heat required to convert 1 kg of a liquid into gas at its boiling point without change in temperature.
Q = m L
where,
Q = heat absorbed or released (J)
m = mass (kg)
L = latent heat (J kg−1)
During change of state, temperature remains constant even though heat is supplied.
Q1. Change of state occurs due to: A) Change in mass B) Change in pressure C) Absorption or release of heat D) Change in volume Answer: C Q2. Latent heat is absorbed or released during change of state: A) With change in temperature B) Without change in temperature C) With increase in temperature only D) With decrease in temperature only Answer: B Q3. Latent heat of fusion is required for: A) Solid to gas B) Liquid to gas C) Solid to liquid D) Liquid to solid Answer: C Q4. Latent heat of vaporization is required for: A) Solid to liquid B) Liquid to gas C) Gas to liquid D) Solid to gas Answer: B Q5. Formula for latent heat is: A) Q = m c ΔT B) Q = m g h C) Q = m L D) Q = F × s Answer: C Q6. SI unit of latent heat is: A) J B) J kg⁻¹ C) kg J⁻¹ D) J K⁻¹ Answer: B Q7. During melting of ice, temperature: A) Increases B) Decreases C) Remains constant D) Becomes zero Answer: C Q8. Which process involves release of latent heat? A) Melting B) Boiling C) Condensation D) Sublimation Answer: C
Conversion of matter from one state to another due to heat exchange.
Heat absorbed or released during change of state without change in temperature.
Q = m L
MCQs and numericals are frequently asked on latent heat, types and heating curve concepts.
