The Chemistry Tutor: Learning by Example DVD Series provides an introduction to chemistry through step-by-step example problems. Emphasis is placed on giving students confidence in their skills by gradual repetition so that the skills learned are committed to long term memory. This episode covers the atomic theory of matter, including how atoms combine together to form new compound, the law of conservation of mass and how the mass of the substances at the beginning of a reaction must equal the mass of the products of the reaction. Grades 9-Adult. 44 minutes on DVD.