The purpose of this research was to develop teaching material of soil used in environmental education and performance tasks used the teaching material and examine how students' awareness and engagement in environmental conservation is growing. A teaching plan and an experimental method associated with acid rain and buffering capacity of pH in soil were developed to give students an opportunity to learn about the function of soil in the environment. The performance task was designed to make students explain the difference of pH between acid rain and water in the river. The questionnaire was also designed, which made students compare what they did in their daily lives with what they were going to do in the future, to reveal students' eagerness to engage in environmental conservation. As a result of it, the lesson showed to raise students' awareness of the function of soil and find the relation between rain and soil. Evaluation of the performance tasks revealed the accuracy of the students' learning. However, the students' responses to the questionnaire did not reveal interest in engaging in environmental conservation.