Effects of STEM Learning Activities on Matthayom Suksa 4 Students’ Problem-Solving Skills and Attitudes Towards Chemistry Learning on Stoichiometry.

The purposes of this research were tostudy the effects of STEM-based learning approach on students’ problem-solving skills and attitudes toward learning the chemistry topic of stoichiometry. This pre-experimental research employed a one-group pretest-posttest design among students. This research sample group consisted of 28 Grade 10thstudents from Srinagarindra the Princess Mother School, Rayong. The research instruments included three STEM-based lesson plans on the topic of stoichiometry, which were deemed highly appropriate (X̄= 4.43 out of 5); a chemistry problem-solving skills test on stoichiometry, with an Index of Item-Objective Congruence (IOC) ranging from 0.60 to 1.00; and an attitude assessment toward learning chemistry, with an IOC ranging from 0.60 to 1.00. All research instruments were verified for quality and considered appropriate for implementation in this study. The study was carried out over 14 instructional periods.After conducting the STEM-based learning activities, the results indicated that 1) students achieved an average score of 70.13% in problem-solving skills, which was higher than the pre-instruction average score of 40.14%. A total of 24 students scored above the 60% proficiency threshold. The learning progress index for problem-solving skills on the topic of stoichiometry was at a moderate level; and 2)students' attitudes towards chemistry learning on stoichiometry were assessed at good level after participating in STEM-based learning activities.Keywords:Attitudes Toward Chemistry, Problem-Solving Skills, STEM Education, StoichiometryJournal of Education, Prince of Songkla University, Pattani CampusVol.36No.2 May –August 2025, pp.146-158.