This web page contains a set of “”drill & skill”” problems for students of chemistry, physics, and engineering. It was developed to provide interactive practice in basics such as significant figures, unit conversion, chemical formulas, rate constants, Avogadro’s Law and Boyle’s Law. Advanced problems allow practice in molecules and compounds, bonding and molecular structure, quantum numbers, chemical kinetics, principles of reactivity, and electron transfer. Most of the exercises are designed to allow answers to be displayed.