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