The following are some units I. Ns II. Non III. Nm$^{-2}$ IV. J°K$^{-1}$ V. JKg$^{-1}$ What are the units of latent heat?

1. Analyze the question

The question asks us to identify the correct SI unit for latent heat from the provided list.

2. Explain the concept

Latent heat is the quantity of heat required to change the state of a substance without changing its temperature. The formula for latent heat ($L$) is:

Where:

• $Q$ is the quantity of heat (measured in Joules, J)
• $m$ is the mass of the substance (measured in kilograms, kg)
• $L$ is the specific latent heat

To find the unit of $L$, we rearrange the formula:

Substituting the units:

3. Show the solution

• I. Ns: This is the unit for Impulse or Change in Momentum.
• II. Nm: This is the unit for Torque or Work (Newton-meters).
• III. Nm⁻²: This is the unit for Pressure or Stress (Pascals).
• IV. J°K⁻¹: This is the unit for Heat Capacity.
• V. Jkg⁻¹: This is the unit for Specific Latent Heat.

Comparing our derived unit ($Jkg^{-1}$) with the list, it matches item V.

4. Identify the answer

5. Exam Tip

When dealing with "Specific" quantities in Physics (like Specific Heat Capacity or Specific Latent Heat), the unit almost always involves "per unit mass" ($kg^{-1}$). If you ever forget the unit, just look at the formula: if it has mass in the denominator, your unit must have $kg^{-1}$!