Khan Academy -- Chemistry"Khan Academy [a 501(c)(3) non-organization] offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. Subjects include math, science, computer programming, history, art history, economics, and more. [Khan Academy has] partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content."