Pedagogical practitioners who emphasise active learning in undergraduate chemistry courses widely use the Student Assessment of Learning Gains (SALG) instrument to measure students' perceptions of their gains in knowledge and skills in chemistry. Although numerous studies have reported SALG results in support of successful pedagogical interventions, a comprehensive construct-verified version measuring students' perceptions of their chemistry learning is lacking. This paper aims to identify latent constructs of the SALG instrument that was administered in Process Oriented Guided Inquiry Learning (POGIL) classes by using exploratory and confirmatory factor analyses. When the SALG was administered on two separate occasions with two different groups of students following four weeks of instruction on topics in stereochemistry, the results revealed a four-factor structure consisting of 32 items that included Active Learning, Concept Learning, Resources, and Process Skills. These findings demonstrate an approach to collect evidence to support the match between intended constructs and measured variables in light of a targeted pedagogical intervention.