Data collection involved the identification of students' existing ideas about energy using semistructured interviews, including the use of Interviews about Events (IAE) approach. Development of IAE focus cards was based on an eight step algorithm developed by Gilbert, Watts and Osborne (1985). All interviews were audio-taped and fully transcribed. The interview began with the researchers showing the participant a card of a sample or object, such as, a dish of fish, a boy running, a boy playing football, a battery, a factory, a power plant, a dam, and coal. The student was then asked whether the sample or the object in a card was somehow related to energy. In case of a positive answer, students were then asked to provide explanations that could elicit his or her understanding about energy, while the interviewer could further probe for clarifications and needed extensions of students' ideas, but without any attempt to modify their initial idea