Research based formative interventions were proposed to different groups of prospective primary teachers (PPT) in three different academic years (2008-2011) to design a formative module on energy for PPT formation. The module included/consisted of CK and PCK parts and parts where CK and related PCK were connected. Different studieswere developed aim to explore the ideas about energy of PPTs and effective strategies than can modifying them giving at the same time a PCK formation. Data were collected from the tutorial worksheets filled by PPTs, the educational paths planned by each PPT for the portfolio, by the PCK questionnaire. It emerges that PPTs before the formative module need criteria to identify energy as physical entity and they do not distinguish between the scientific use of the concept of energy and those in the everyday life. After the formative module they evidenced improvement in CK as well in PCK related to the concept of energy.