This student-friendly introduction to the principles and calculations used in the field of chemical, petroleum, and environmental engineering is designed to help students 1) develop systematic problem-solving skills, 2) learn what material balances are, how to formulate, apply, and solve them, 3)  learn what energy balances are and how to apply them, and 4) learn how to deal with the complexity of big problems. Self-contained in approach, it provides all necessary background information on units and measurement, physical properties, basic laws about the behavior of gases, liquids, and solids, and some basic mathematical tools.