Background:
Research in Science Education has shown that often students need to learn how to identify differences and similarities between descriptive and explicative models. The development and use of explicative skills in the field of thermal science has always been a difficult objective to reach. A way to develop analogical reasoning is to use in Science Education unifying conceptual frameworks.

Material and methods:
A questionnaire containing six open-ended questions on thermally activated phenomena was administered to the students before instruction. A second one, similar but focused on different physical content was administered after instruction. Responses were analysed using k-means Cluster Analysis and students’ inferred lines of reasoning about the analysed phenomena were studied.

Results:
The pre-instruction results show that the students reasoning lines were mainly oriented to the use of lines of reasoning based on the use of memory of past studies and on an application of mathematics without a search for a proper mechanism of functioning. After instruction, these lines of reasoning seem to have clearly evolved to explicative ones.

Conclusions:
Students reasoning lines seem to have clearly evolved to explicative ones and it is reasonable to think that the Feynman Unifying Approach has favoured this change.