Of possible microstates means an increase in entropy. Solid to liquid to gas means an increase in the number There's an increased freedom of movement. So in general, as we go fromĪ solid to a liquid to a gas, there's an increase in the number of possibleĪrrangements of particles. And gases, if we assume ideal gases, there are no intermolecularįorces between the particles. Liquids are held togetherīy intermolecular forces. Solids are held togetherīy either chemical bonds or by intermolecular forces. Of microstates available to solids, liquids, and gasses. The reason why this is generally true has to do with the number Molar entropies than liquids, as we can see comparing the values, and liquids, in general, have higher standard molarĮntropies than solids. Looking at these numbers, in general, gasses have higher standard Molar entropy of 69.9, and methane gas has a standard Let's compare that solid to two other standard molar entropies. Molar entropy of carbon in the form of graphite is equal to 5.7 joules per kelvin mole. Of different substances at 25 degrees Celsius. Next let's look at a table showing standard molar entropies Therefore, the standard molar entropy of graphite is referring to the entropy value for one mole of a pure solid under a pressure of one atmosphere. In our case, we're talkingĪbout one mole of carbon in the form of graphite Talking about a solution with a concentration of one molar. Is referring to the pure gas at a pressure of one atmosphere. Solid or pure liquid under a pressure of one atmosphere. By convention, the standard state of a solid or liquid is referring to the pure The superscript, not, refers to the standard However, when we write standard molar entropies, we don't include the delta sign and we reserve theĭelta sign for processes such as phase changes orĪlso chemical reactions. Of a hypothetical crystal at zero kelvin. So really it's a change in entropy and therefore it would be 5.7 minus zero with zero being the entropy Perfect crystal of graphite at zero kelvin. Of graphite is positive because it's being compared to a hypothetically With one mole of graphite, we could write the unitsĪs joules per kelvin mole.

Graphite at 25 degrees Celsius is equal to 5.7 joules per kelvin. Standard entropy refers to the absoluteĮntropy of a substance at a pressure of one atmosphere and a specified temperature. Have one mole of carbon in the form of graphite. Now that we understand theĬoncept of zero entropy, let's look at the entropy of a substance. K is equal to 1.38 times 10 to the negativeĢ3rd joules per kelvin. We can get the units for entropy from the Boltzmann constant, K. Greater than zero kelvin, the entropy must be greater than zero, or you can say the entropy is positive. Since we started with zeroĮntropy at zero kelvin, and the entropy increases, at all temperatures that are In the number of microstates, according to the equationĭeveloped by Boltzmann, that also means an increase in entropy. Means the particles gain energy and have motion around Next, let's think about what happens to our hypothetically perfect crystal if we increase the temperature. Is equal to zero at zero kelvin for this pure crystalline substance. Microstates is equal to one, the natural log of one is equal to zero, which means that the entropy So when we think about our equation, if we plug in the number of One possible arrangement for these particles. In their lattice states with no thermal motion. So all of the particles are perfectly ordered

Substance at absolute zero, all of the particles are perfectly ordered in their lattice states. Microscopic arrangement of all of the positions and energies of all of the particles. We can think about why theĮntropy is equal to zero by looking at the equationĭeveloped by Boltzmann, that relates entropy, S, to At zero kelvin, the entropy of the pureĬrystalline substance, S, is equal to zero.

Is equal to zero kelvin or absolute zero. And that point is reached forĪ pure crystalline substance when the temperature Measured on an absolute scale, which means there is a

Standard absolute entropies at 298k