We're going to be honest: we do Physics. That's why this is called The Physics Classroom website. And when we do the Teacher's Notes section for our Concept Builders, we typically have a lot to say ... and a lot of resources to point you to. We're not claiming to be ignorant of chemistry; we just don't have a lot of resources here at The Physics Classroom to point you to. And so this page is going to be a lot shorter than our usual page that accompanies our Physics Concept Builders. That's our honest confession.

If you teach chemistry, you likely subscribe to the importance of providing students with a strong background in relating formulas and words to a mental picture that describes a sample of atoms and molecules. And that is what this Concept Builder aims to do. The goal is to help students make the connection between a particle representation of atoms and molecules to the words that we use to describe that representation and the formulas that we use to describe that representation.

Like all our Concept Builders, this Concept Builder is intended as an in-class activity to help develop conceptions of atoms, molecules, elements, and compounds and of the formulas and words which we use when referring to them. We recommend that after some preliminary discussion, defintions, examples, and maybe even some modeling activities, allow students an opportunity to interact with the questions. This Concept Builder consists of three separate difficulty levels. The Apprentice Difficulty Level has only 6 questions. The questions provide a simple particle representation consisting of combinations of three elements - existing both as individual elements and as compounds. Three of the questions ask students to identify the one verbal statement that  does not match the representation. And three of the questions ask students to identify the one formula that does not describe the representation.

The Master Difficulty Level also includes six questions, but the particle representations and accompanying questions are slightly more complex. Three of the questions ask students to identify the one verbal statement that describes the representation. And three of the questions ask students to identify the set of formulas that describes the representation.

Finally, the Wizard Difficulty Level also includes six questions, but the particle representations (includes four elements) and accompanying questions are more complex. Three of the questions ask students to identify the one verbal statement that describes the representation. And three of the questions ask students to identify the set of formulas that describes the representation.


In order to complete a level, a student must correctly analyze each question of that level. If a student's analysis is incorrect, then the student will have to correctly analyze the same or very similar question twice in order to successfully complete the level. This approach provides the student extra practice on questions for which they exhibited difficulty. As a student progresses through a level, a system of stars and other indicators are used to indicate progress on the level. A star is an indicator of correctly analyzing the question. Once a star is earned, that question is removed from the que of questions to be analyzed. Each situation is color-coded with either a yellow or a red box. A red box indicates that the student has incorrectly analyzed the question and will have to correctly analyze it twice before earning a star. A yellow box is an indicator that the question must be correctly analyzed one time in order to earn a star. Once every question of a difficulty level has been analyzed, the student earns a trophy which is displayed on the Main Menu. This system of stars and trophies allows a teacher to easily check-off student progress or offer credit for completing assigned levels.

The most valuable (and most overlooked) aspect of this Concept Builder is the Help Me! feature. Each question group is accompanied by a Help page that discusses the specifics of the question. This Help feature transforms the activity from a question-answering activity into a concept-building activity. The student who takes the time to use the Help pages can be transformed from a guesser to a learner and from an unsure student to a confident student. The "meat and potatoes" of the Help pages are in the sections titled "How to Think About This Situation:" Students need to be encouraged by teachers to use the Help Me! button and to read this section of the page. A student that takes time to reflect upon how they are answering the question and how an expert would think about the situation can transform their naivete into expertise.