Many pupils have difficulty explaining why the temperature of a sample of a substance remains constant during a change of state, even though it is being continually heated or allowed to cool

Energy and Thermal Physics


Resources to Address This

  • Examination of boiling (11-16)

    Ref - Practical physics; Molecules; Changes of phase; Examination of boiling

    This activity follows the heating of a liquid until it boils.  The explanation then introduced Latent Heat.

    • Bubbles cannot form and grow in the liquid until the vapour pressure in them matches the outside atmospheric pressure. The liquid boils away as fast as heating provides the 'exit-taxi' of latent heat. Once the liquid is boiling, further heating simply equips more molecules with speed needed to evaporate into vapour bubbles. Therefore, the temperature stays constant at the boiling point.
    View Resource


  • Jasien, P. G. () Roles of Terminology, Experience and Energy Concepts in Student Conceptions of Freezing and Boiling, Journal of Chemical Education, 90,


    Review sheet

  • Chu, H; Treagust, D. F.; Yeo, S. and Zadnik, M. () Evaluation of Students' Understanding of Thermal Concepts in Everyday Contexts, International Journal of Science Education, 34, (10)


    Review sheet


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