Welcome to the world of chemistry. A magical world that will help you understand many of the chemical phenomena you encounter daily around you. Have you ever wondered what particles make up the materials found in nature? What properties of materials do we exploit to construct various objects? What processes do we follow after transforming them into new materials? Why are oxygen and carbon dioxide such important gases? These are just some of the questions for which you will find answers in the chemistry of the 2nd grade of middle school.
So, through this aid (as well as the corresponding aid I wrote for the physics of the 2nd grade of middle school), I will try to help you fully understand all the new concepts you will learn, so that you can successfully cope with your studies. [...]

(from the author's preface)