An inquiry-based laboratory learning unit was designed to enhance high school students' understanding of the application of lipase as a catalyst to synthesize isoamyl and geranyl ester derivatives as well as to promote their understanding and positive perceptions of green chemistry. The learning unit consisted of three laboratories and a final presentation. The first laboratory activity allowed students to learn how to adjust macroscale titration techniques to microscale titration techniques so that the method could be used for quantitative determination of ester products in the next two laboratory activities. The second laboratory activity introduced students to a greener way to synthesize ester compounds by replacing a harmful strong acid catalyst with a more environmentally friendly catalyst, an enzyme lipase. The third laboratory activity challenged students to design their own experiments to synthesize other esters using lipase-catalyzed esterification reactions. At the end of the learning unit, students in each group presented the results and conclusions of the third laboratory activity to the whole class and explained how the 12 principles of green chemistry were applied in the laboratory. The results from the Learning Unit Conceptual Test and Learning Unit Perceptions Questionnaire indicate that the learning units can promote students conceptual understanding. They also have positive perceptions toward green chemistry and learning units.

A simple inquiry-based activity called “Fruit Puzzle” was designed to investigate high school students’ understanding of the relationship between the concepts of density and solution concentration at a submicroscopic level. The first activity allowed students to predict whether five types of fruit would sink or float in water and asked them to explain the reason for their prediction. This activity aims to investigate their prior knowledge of the concept of density. Then, the students were asked to experiment and observe the result. In the second activity, students were challenged to design and perform an experiment to compare the density of each type of fruit using table salt or sugar and water. Finally, in the third activity, students were tasked with designing a method that would allow the fruit to stay in the solution without sinking or floating. Two postlaboratory questions were used to investigate how students could relate the concept of density to the solution concentration at both the submicroscopic and symbolic levels. The sample size of this study was 98 Thai students in grade 9. The results from the activity sheet showed that students could relate the concept of density with the sink and float phenomenon in the prediction activity and could relate the concept of density with the concentration of the solution in the experiment-planning step. However, the results from the postlaboratory questions indicated that the students still found it difficult to explain the concepts at both the submicroscopic and symbolic levels.

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