High school students at Ramwittaya Rachamunklapisek School in Thailand in previous years had records of low learning
achievement in chemistry, especially in the area of chemical reaction rates. They also had low levels of integrated science process
skills due to lack of experience in inquiry activities. This study aimed to improve students’ achievement records and integrated
science process skills through 12 hours of science inquiry activities. Sixty-three grade 11 students at the school participated in the
study in second semester of 2011. The paired-sample t-test analysis showed that students’ post-achievement score (mean 26.13,
SD 6.40) were statistically higher than their pre-achievement score (mean 8.75, SD 2.51) at p-value less than 0.001. They also
obtained an average of 74.52% in integrated science process skills (good level). It was found that predict-observe-explain
activities effectively engaged students in the first step and throughout the inquiry learning process. Science inquiry activities
effectively enhanced students’ learning achievements and integrated science process skills.