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.
Acid-base chemistry is a common topic in a introductory chemistry course. Such a unit often begins with a discussion of the observable properties that make and acid different than a base. Distinguishing acids from bases based on observable properties is the focus of this Concept Builder. There are three levels of difficulty in the Concept Builder. In the first level of difficulty (
Apprentice Level), students must recognize an acid or a base on the basis of its pH value, a litmus test, and the label on a lab bottle. In the second level of difficulty (
Master Level), students must be able to do everything from the Apprentice Level and additionally relate the following to acid-base identity: the relative pH-pOH values, the hydronium ion concentration, the results of a phenolphthalein test, the chemical property of acids reacting with metals, and the physical property of bases feeling slippery. And finally in the third level of difficulty (
Wizard Level), students must be able to do everything from the previous levels and additionally be able to relate the following to acid-base identity: the hydroxide ion concentration, the color of pH paper, and the sour taste of acids.
The Concept Builder is modeled after a popular children's exercise that goes like ... "One of these things is not like the other. Which one doesn't belong?" In the Concept Builder, there might be four statements given. Three of the statements are characteristic of acids and the fourth is not. Students must determine which one of the four does not belong; that is, which one is not like the other ones.
The three difficulty levels are differentiated as follows:
- Apprentice Difficulty Level: Question Groups 1-4 ... Each question includes three acid-base property statements.
- Master Difficulty Level: Question Groups 1-8 ... Each question includes either three or four acid-base property statements. Four of the Question Groups in this difficulty level are the four Groups from the Apprentice Difficulty Level.
- Wizard Difficulty Level: Question Groups 5-12 ... Each question includes four or five acid-base property statements. Four of the Question Groups are from the Master Difficulty Level.
To provide a complete experience without any redundancy, teachers should assign the Apprentice and the Wizard Difficulty Levels.
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 have the same type of representations) but not identical.