Explanation studies underlined the importance of using evidence in support of claims. However, few studies have focused on students' use of others' data (second-hand data) in this process. In this study, students collected data from a local water source and then took all the data back to the classroom to create scientific explanations by using claim-evidence-reasoning model on a new mobile application. A middle school science teacher from a Midwest town participated with four sixth-grade classes. After collecting their own data from a local water source, students created explanations by analyzing the data they collected (first-hand data), and by analyzing existing data set collected by another school from another river (second-hand data). By analyzing the health of these two water sources, students created two scientific explanations. Students participating in this study created stronger explanations when analyzing the data they generated (first-hand data).