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.

Most Chemistry courses have a unit on electrochemistry or oxidation-reduction. At the heart of such topics is an understanding of oxidation state and its use in predicting whether a substance has been or will be oxidized or reducted in a reaction. This Concept Builder includes plenty of practice for students to identify the oxidation state of elements in a given species. There are a total of 60 questions organized into 16 Question Groups and spread across three differentiated difficulty levels. 

Here is the breakdown of the difficulty levels:

• Apprentice Difficulty Level: Question Groups 1-6 ... Students are given the formula of a simple species (e.g., element, monatomic ion, binary ionic compound, etc.) and must determine the oxidation state of the elements in the atom, ion, or compound.
• Master Difficulty Level: Question Groups 7-12 ... Students are given the formula of a compound or a polyatomic ion and must determine the oxidation state of the elements in the compound or ion.
• Wizard Difficulty Level: Question Groups 13-16 ... Students are given the formulas of three species that have one element other than oxygen or fluorine in common (e.e., nitrogen, sulfur, chlorine, or carbon) and must determine the oxidation state of that element in each of the species. 

Teachers are encouraged to view the Questions or to do the Concept Builder in order to judge which difficulty levels are most appropriate for their classes. The three difficulty levels are scaffolded such that doing all three in order makes for an effective learning experience. The levels become progressively more difficult. For a student who knows the rules for assigning oxidation states to elements, the activity will go quite quickly. For those students who are progressing towards an understanding of the rules, the activity will be quite useful. For those students who don't know there are such rules, a tap on the Help Me! button is recommended. The questions can be viewed by logged-in teachers on a separate page.  View Questions.

There are 3-4 similar questions in every Question Group; the similarity has to do with the type of species presented to the student. If a student misses a question from within a particular Question Group, then they will have to answer two different questions correctly (without any further miss) from that same Question Group. This strategy provides students extra practice on their most troublesome questions.

Like all our Concept Builders, this Concept Builder utilizes a variety of strategies to make each student's experience different. The ordering of questions is random. The Question number assigned to each question is scrambled. For instance, two side-by-side students will not have the same question for question number three. And questions are organized into "groups"; the question a student receives is selected at random. In the end, two side-by-side students will have quite different experiences.

For those with Task Tracker accounts, the Concept Builder also keeps track of student progress. It requires that students demonstrate a mastery of questions in each Question Group. If they miss a question from one group, then they will have to answer two consecutive questions correctly in order to demonstrate mastery. Progress is displayed in the progress report on the right side of the Concept Builder. A star indicates a demonstration of mastery. A question with a red background indicates that the student has missed the question. And a question with a yellow background means that the student must get one more question from that Question Group correctly answered in order to obtain a star. When an activity is completed, the student will be awarded a Trophy. This Trophy is displayed on the Main Menu screen. These strategies make the Concept Builder an ideal addition to the 1:1 classroom and other settings in which computers are readily available. 

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.