With the goal that the students of ninth grade learn the concept of thermal dilatation and at the same time motivate them to get more interested on real-life Physics phenomena; we applied the cognitive sub-theories concepts from the point of view of Conceptual Pedagogy, using the „concept‟ like knowledge approach, the „mentefacto‟ as representation of concept tool and pertinent intellectual operations as stated by the Conceptual Pedagogy model. It was used the group technique called „la rejilla‟ with the students, a selected text was socialized with students and it was able to get easily for each student to read it anytime and anywhere. The ages of students are between 13 and 15 years old. The text should have an implicit and explicit manner to show the essential characteristics of thermal dilatation; the model describes how to define the upper class concepts and the different class concepts. Results shown that applying the method students get a better knowledge and long term of the concept studied.