Classify each segment before calculation Draw the process in words: warming solid, melting, warming liquid, boiling, warming vapour. Mark where temperature changes and where it stays constant; then assign Q = mc Delta theta or Q = mL segment-wise before substituting numbers.

Memorise standard latent heat values with units Lock ice fusion as 80 cal g^-1 or 336 J g^-1 and water vaporization as 536 cal g^-1 or 2260 J g^-1. In one-step MCQs, unit mismatch (g vs kg, cal vs J) causes most wrong answers even when concept is correct.

Check pressure condition first If external pressure changes, boiling point changes and latent heat can shift. Apply the text rule that boiling occurs when saturated vapour pressure equals external pressure, then interpret whether vaporization starts earlier or later.

Handle melting-point exception explicitly For substances that contract on melting, such as water, increasing pressure decreases melting point. For most substances that expand on melting, increasing pressure raises melting point; do not generalize one behavior to all materials.