# Entropy Activity

-Introduction

-The reaction coordinate

-The energy landscape

-Population distributions

-Motion at constant temperature, and exchange of energy with the heat bath

-Thermally activated processes

-Energy and temperature determine the populations

-Entropy and free energy

-Mathematical derivation of free energy

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# Online Entropy Activity

This set of lessons and applets is assigned as a part of your homework on the topic of entropy. Each concept is accompanied by a series of virtual exercises involving an applet to aid in understanding of that concept. Each lesson includes a set of questions which you are required to complete and turn in. (See download below link)

## Activity Handout

For easy reference, you may download a printable version of this activity.

• Online Activity Handout [15 pages to follow along with activity, not to be turned in. All content in this handout is also present on the site. The handout is provided for those who would rather read a printout than a computer screen.]

• Online Activity Questions [2 pages of questions to be turned in with your homework assignment]

## Introduction

The goal of this activity is to provide insight into the ways modern science views the effects of temperature on chemical reactions, including especially thermally activated processes. Schematic diagrams of the type shown below, and used in lecture, have tremendous power when thinking about such processes at the molecular level.

The diagram shows the energy associated with a thermally activated process in which a chemical system transitions between two states, labeled state 1 and state 2. State 2 is a stable state because it corresponds to the lowest energy configuration. State 1 is a metastable because, although it has higher energy than state 2, the system must overcome an activation barrier to transition from state 1 to state 2. In many cases, the barrier is so high that the metastable state can exist for a very long time. For instance, diamond is a higher-energy form of carbon than graphite and so is, in principle, a metastable form of carbon. However, the barrier between the diamond and graphite form of carbon is so high that you are not in any danger of having your diamond necklace spontaneously convert into graphite. For chemical processes with lower barriers, transitions from metastable to stable states do occur and diagrams of the type above are the primary means through which scientists understand such processes. We will therefore begin by exploring the meanings of various features of the above diagram and how it is used to think about chemical processes.

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