Most science teachers are amazed when grading tests and quizzes, often wondering how and why students have reached a conclusion, particularly when students fail to provide a detailed account of their logic. Ideally, a variety of assessments should be used to identify alternate student conceptions or gaps in understanding, particularly when preparing students for state-mandated exams. With this in mind, a free internet-based software package, IMMEX (interactive multimedia exercises) was designed to use authentic scenarios to gauge students’ problem-solving skills and science knowledge.