DECREASE IN ENTROPY FULL

The food dye molecules initially occupy a much smaller volume (the drop of dye solution) than they occupy once the process is complete (in the full glass of water). This process yields a much lesser dispersal of matter, since the molecules will occupy a much lesser volume after the solid-to-gas transition. (b) Condensation is the conversion of a gas (relatively low density) to a liquid (much greater density). This process yields a much greater dispersal of matter, since the molecules will occupy a much greater volume after the solid-to-gas transition. (a) Sublimation is the conversion of a solid (relatively high density) to a gas (much lesser density). (credit a: modification of work by Jenny Downing credit b: modification of work by “Fuzzy Gerdes”/Flickr credit c: modification of work by Sahar Atwa)

A drop of food coloring added to a glass of water forms a solution with uniform color.

Redistribution of Matter during a Spontaneous Processĭescribe how matter is redistributed when the following spontaneous processes take place: In each case, a spontaneous process took place that resulted in a more uniform distribution of matter or energy. When two objects at different temperatures come in contact, heat spontaneously flows from the hotter to the colder object.Īs illustrated by the two processes described, an important factor in determining the spontaneity of a process is the extent to which it changes the dispersal or distribution of matter and/or energy. This spontaneous process resulted in a more uniform dispersal of energy. From the perspective of this two-object system, there was no net gain or loss of thermal energy rather, the available thermal energy was redistributed between the two objects. This corresponds to a loss of thermal energy by X and a gain of thermal energy by Y.

When these objects come into contact, heat spontaneously flows from the hotter object (X) to the colder one (Y). Now consider two objects at different temperatures: object X at temperature T X and object Y at temperature T Y, with T X > T Y ( Figure 2). Once the valve is opened, the gas spontaneously becomes evenly distributed between the flasks. An isolated system consists of an ideal gas in one flask that is connected by a closed valve to a second flask containing a vacuum. After the spontaneous process takes place, the matter distributes both more widely (occupying twice its original volume) and more uniformly (present in equal amounts in each flask). Initially, the system was comprised of one flask containing matter and another flask containing nothing. Instead, the driving force appears to be related to the greater, more uniform dispersal of matter that results when the gas is allowed to expand. The spontaneity of this process is therefore not a consequence of any change in energy that accompanies the process. The first law of thermodynamics confirms that there has been no change in the system’s internal energy as a result of this process. Since the system is isolated, no heat has been exchanged with the surroundings ( q = 0).

Recalling the definition of pressure-volume work from the section on thermochemistry, note that no work has been done because the pressure in a vacuum is zero. When the valve is opened, the gas spontaneously expands to fill both flasks.

Initially there is an ideal gas on the left and a vacuum on the right ( Figure 1). | Key Concepts and Summary | Key Equations | Glossary | End of Section Exercises | Dispersal of Matter and EnergyĪs we extend our discussion of thermodynamic concepts toward the objective of predicting spontaneity, consider now an isolated system consisting of two flasks connected with a closed valve. Predict the sign of ΔS of a system for a given chemical or physical process.Determine relative entropies of different substances with respect to their physical state and complexity of the molecule.Differentiate between and determine the number of macrostates and microstates in a simple system of gas molecules, and explain why there is a higher probability that energy will be dispersed than it will be concentrated in a small number of nanoscale particles.

Decrease in entropy