Most Chemistry and Physics courses include a considerable amount of attention to the use of the metric system. Units such as meters, grams, and liters are common-place within the course. And derivative units formed by adding Greek prefixes to such base units are also common. These units show up in labs, in discussions, and in problems. And often times it is necessary for students to perform conversions between units - for instance, from cm to m. This Concept Builder is designed to provide students practice with converting among a variety of metric units, particularly units formed from Greek prefixes kilo-, centi-, and milli-.

Each question involves two tasks - one having to do with decimal point movement and the other having to do with how to conduct the conversion on a calculator. Students must complete both tasks to answer a question correctly. Our intent was that requiring both tasks would assist students in associating them with each other. For instance, some students are quite comfortable with moving a decimal point a given number of locations but have difficulty with how to perform the calculation on their calculator. Such students will quickly recognize that moving a decimal point two places to the left is equivalent to dividing by 100.

The interface is very intuitive. Arrows are used to move a decimal point. The graphical display uses arrows to show the number of decimal places that the decimal point has been moved. A verbal statement is also used to summarize the direction and the number of places that the decimal place has been moved. When necessary, trailing and leading zeroes are added onto the graphical display. The decimal point is always shown since the attention of the student will be on decimal point movement. However attention to significant figures is demonstrated by the appearance of the decimal point. A hollowed-out version of a decimal point is displayed if the trailing zeroes are not significant. A filled-in decimal point is shown when the zeroes are significant.

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" with questions within the same group being very similar (for instance, they may require the same type of unit conversion) but not identical. 

This Concept Builder consists of three distinct difficulty levels, each of which includes six question groups. in the Apprentice Difficulty Level, students must convert from: kilo ==> base unit, centi ==> base unit, and milli ==> base unit. There are also three conversions in the opposite direction - that is beginning with the base unit and converting to the derivative unit.

In the Master Difficulty Level, students must convert from: kilo ==> milli, milli ==> kilo, kilo ==> centi, centi ==> kilo, milli ==> centi, and cent ==> milli, And finally in the Wizard Difficulty Level, conversions are slightly more complicated as the nano- and the micro- Greek prefixes are introduced and used alongside the kilo-, centi-, and milli- Greek prefixes.

In order to complete a difficulty 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.