Jasien (2013)

Researchers analyse student conceptions of solid-liquid and liquid-vapour phase transitions using data from 117 undergraduate chemistry students, using data from open-ended, short-answer questions. The collected responses offer insights into students' understanding of these phase changes.


  • Teachers should explicitly point out the differences between scientific versus colloquial meanings of terms.
  • A greater proportion of time should be devoted to the hands-on lab component of science classes.
  • Showing various organic substances boiling at "low" temperatures would be powerful real-world examples and would be important in illustrating phase changes for substances other than water.
  • Classroom demonstrations lead to a significant increase in understanding. These were most effective when targeting concepts not included in the curriculum.

Learners’ ideas

  • Many students conflated physical changes with chemical changes.
  • Many students believed that the sizes of atoms changed during a phase transition.
  • Some students could not identify the composition of bubbles in a boiling liquid, with some younger students believing bubbles were composed of heat.
  • Several students only associated evaporation with water or water solutions, not with other liquids.
  • Some students assumed that a substance such as alcohol had the same freezing point as water.
  • Some younger students viewed evaporation and boiling as the same process.
  • Some students believed that the maximum temperature for a substance is its boiling point.
  • Some students from middle school upwards have difficulty understanding that during a phase transition, the addition of heat does not produce a temperature rise.
  • Some students interpreted crystallisation or precipitation as being the same as freezing.
  • Many students could not correctly identify the relationship between exothermic, endothermic processes and thermodynamic concepts such as 'warm' or 'cold'.
  • Some students had difficulty reconciling the ideas of molecular motion with thermodynamic concepts such as 'warm' or 'cold'.
  • Many students had difficulty clearly distinguishing systems and surroundings.

Study Structure


To present students' conceptions of the solid-liquid and liquid-vapour phase transitions and to investigate to what extent students use experience or contextual understandings in their explanations.

Evidence collection

Evidence was produced via a simple survey of four short-answer questions designed for this study. The survey was completed after the topics in question had been taught (though the time between teaching and evaluation ranged from a few days to weeks). Multiple choice elements of the questions were analysed statistically.

Details of the sample

The sample consists of 117 students from two different cohorts of a first-semester undergraduate general chemistry course at a midsized public university.

Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today