Consider again the two examples illustrated in Figure 3.1: a...

Name: Problem 1, Chapter 17: Thermodynamics: A complete undergraduate course
Uploaded: 2020-12-14T17:15:33-08:00
Duration: 5 min 40 s
Channel: Jennifer Hudspeth
Description: Consider again the two examples illustrated in Figure 3.1: a ball rolling in a bowl, and an atom emitting a photon. Do not discuss the whole universe. Rather, choose some suitable boundary to define the system under discussion, identify the constraints, and hence identify what property of the system dictates the direction of the process.

Consider again the two examples illustrated in Figure 3.1: a ball rolling in a bowl, and an atom emitting a photon. Do not discuss the whole universe. Rather, choose some suitable boundary to define the system under discussion, identify the constraints, and hence identify what property of the system dictates the direction of the process.

Key Concepts

System Boundaries

Defining the system boundaries involves choosing a precise area of interest within a larger context so that one can focus on the dynamics occurring in that selected region while excluding influences from the broader environment. This concept is essential in thermodynamics and statistical mechanics, as it determines which components are included in the analysis of conservation laws and which interactions can be neglected, thereby shaping the theoretical framework for understanding system behavior.

Constraints

Constraints refer to the conditions or conservation laws—such as conservation of energy, momentum, or particle number—that are imposed on a system based on its defined boundaries. These restrictions limit the set of possible states or transitions available to the system, and their proper identification is crucial for predicting the evolution of the system, understanding allowable processes, and establishing equilibrium or non-equilibrium conditions.

Thermodynamic Direction (Entropy and Free Energy)

The property dictating the direction of a process often hinges on the concept of entropy and, in some contexts, free energy. In isolated or closed systems, the second law of thermodynamics tells us that processes tend to move in the direction of increasing entropy, while in systems with fixed temperature, pressure, or other constraints, changes in free energy may determine stability and the evolution of the process. This directional bias provides an 'arrow of time' indicating the natural progression toward thermodynamic equilibrium.

Transcript

00:02 Hi there.

00:02 In this question, we have a chick developing inside an egg, inside an incubator, and we want to talk about the entropy changes.

00:12 So in order to talk about entropy changes, we need to first define the system and the surroundings.

00:20 So the developing chick is going to be the system.

00:31 So that developing embryo, that is going to be the actual system.

00:49 For the surroundings, that's going to be everything else.

00:58 So if we think about it, what everything else would mean.

01:02 That's going to be those proteins, carbohydrates, and lipids that are discussed in the problem.

01:15 These are, of course, for the most part, macro molecules.

01:23 And since they are macromolecules, they have pretty low entropy.

01:27 Let's see.

01:27 What else do we have? we have the actual shell itself as part of the surroundings.

01:36 And then everything outside the shell, the rest of the world.

01:53 Okay.

01:53 So that would be our system and our surroundings.

01:59 So let's talk about some entropy changes.

02:01 As the chick develops, of course, that is decreasing in entropy.

02:06 We're taking disorder and making something very orderly out of it, making a living organism as that chick develops.

02:12 So the developing chick would represent a decrease in entropy.

02:29 But let's think about what is being used for the development of that chick...

Please give Ace some feedback