Physics·Thermal Physics · NSSCO 3.2.3
Melting, boiling & evaporation
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Heat a solid and it melts; heat a liquid and it boils. But here is the surprise that catches so many learners: while a substance is changing state, its temperature does NOT rise, even though heat keeps pouring in. That hidden heat is called latent heat, and we find it with E = m × L. We'll also meet evaporation — the quiet cousin of boiling that happens at any temperature — see what speeds it up, and read the flat plateaus on heating and cooling curves.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 3.2.3):
- Describe melting and boiling as energy input WITHOUT a change in temperature
- Define melting point and boiling point as the temperatures at which a change of state occurs
- Explain latent heat of fusion (melting) and latent heat of vaporisation (boiling), and recall and use E = m × L
- Distinguish between boiling and evaporation
- State the factors that affect the rate of evaporation
- Plot and interpret heating and cooling curves, and explain the flat plateaus
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Ms Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.