How can we help students develop an understanding of chemistry that integrates conceptual knowledge with the experimental and computational procedures needed to apply chemistry in authentic contexts? The current work describes ChemVLab+, a set of online chemistry activities that were developed using promising design principles from chemistry education and learning science research: setting instruction in authentic contexts, connecting concepts with science practices, linking multiple representations, and using formative assessment with feedback. A study with more than 1400 high school students found that students using the online activities demonstrated increased learning as evidenced by improved problem solving and inquiry over the course of the activities and by statistically significant improvements from pre- to posttest. Further, exploratory analyses suggest that students may learn most effectively from these materials when the activities are used after initial exposure to the content and when they work individually rather than in pairs. [For the corresponding grantee submission, see ED585229.]