This study investigates the various conceptions held by K-8th Korean grade students regarding the 'changes of state' and the 'conditions for changes of state'. The study used a sample of five kindergarteners, five secondgrade students, five fourth-grade students, five sixth-grade students, and five eighth-grade students. The 25 students attend schools in a rural district of South Korea. Some activities that involved a change in the state of water, including condensation, solidification, and melting, were chosen from K-8th grade science textbooks and attempted by the students. Subsequently, we conducted interviews with the students. While most kindergarteners and second-grade students were able to perceive the phenomena involving changes of state, they were unable to express conceptions related to the changes of state and the conditions under which the state the changes. The upper-grade students, on the other hand, had some conception of the invisible gas state. Most of these students held conceptions about the boiling water's change of state from liquid to gas, but few of them held conceptions about the changes of state involving condensation. Most students understood heat and temperature as conditions of the changes of state, but only applied the heat concept to situations involving rising temperatures. In situations involving cooling, students applied the temperature concept. The younger students understood the concept of heat without understanding the concept of temperature.