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.

This Concept Builder focuses on the concept of spontaneous reactions and the ability to predict spontaneity from the knowledge of the enthalpy change and entropy change signs. The Concept Builder is composed of three unique and independent activities. While you can pick and choose the ones that you feel would be helpful, we recommend that you assign each one. The first two activities - Two Truths and a Lie and Matching Pairs will not take a long time. The third activity - Reaction Analysis - is an application of the core concept presented in the Matching Pairs activity. It will require a bit more thinking and analysis but it won't take students an excessive amount of time to complete.

Our summary of the three activities is as follows:
 

• Two Truths and a Lie: 3 questions in which students must identify the false statement from among three statements made about the meaning of spontaneity and the cause of spontaneity.
• Matching Pairs: 1 multi-faceted question in which students must match four pairs of terms associated with the relationship between the sign on ∆H and ∆S and the spontaneity of a reaction.
• Reaction Analysis: 6 questions in which the ∆H and ∆S values for a reaction are stated; students must decide under what conditions the reaction is spontaneous - always, never, at higher temperatures only, or at lower temperatures only.

The questions are shown on a separate page (viewable by logged-in teachers only). Teachers are encouraged to view the questions in order to judge which activities are most appropriate for their classes and what level of preparation would be required. We recommend doing the activities in order. There is no redundancy in the actvitiies. While they are independent activities, they have been designed to be scaffolded such that one activity builds on the confidence that was derived from the previous activity.

Our Concept Builders typically utilize a variety of strategies to make each student's experience different. The main strategy employed here is to provide multiple tables for each level. A table is selected at random and presented to the student. This reduces the likelihood that two side-by-side students would have the same question. 

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. Questions are organized into "groups" with questions within the same group being very similar (for instance, they have the same type of information as "givens") but not identical. Students are randomly selected one of the questions from among the Group. And finally, in the Matching Pairs activity, we scramble the location of the various terms. 
 

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.