Gas Laws and Thermodynamics

Introductory Chemistry - ideal gas lawThe gas laws are a set of principles that relate changes of pressure, temperature, volume, and number of atoms to each other. These laws involve ideal gases (gases that have certain properties that are not usually seen in nature) in introductory chemistry but the general concepts still work. There are five laws for ideal gases:

  • Boyle’s Law
  • Charles’ Law
  • Gay-Lussac’s Law
  • Avogadro’s Law
  • Combined Gas Law

Boyle’s Law involves two systems with different pressures and volumes which two systems are inversely proportional to each other.

Charles’ Law compares volume and temperature and they are proportional to each other.

Gay-Lussac’s Law compares pressure and temperature which are proportionally related.

Avogadro’s Law involves volume and number of moles of atoms which are proportionally related.

Finally, the Combined Gas Law takes all four variables and relates them to each other. Pressure times volume is inversely proportional to a gas constant times number of moles of atoms times temperature.

Thermodynamics helps explain some characteristics of reactions such as how much energy is released or absorbed during the reaction, is the reaction spontaneous (will it occur naturally, not the rate at which it will occur), and the enthalpy (energy in a system) and entropy (function in thermodynamics that involves certain variables) of a system. Some of the key things to learn about thermodynamics are:

  • First and second laws of thermodynamics
  • Hess’s Law
  • Gibbs Free Energy

The first law is the concept that energy is conserved. It may be lost from the system being observed or transferred to another object, but it cannot be destroyed.

The second law states that if the entropy of the system is positive, then the reaction will occur at some rate.

Hess’s Law is based around the first law in how energy is conserved in a system.

Gibbs Free Energy focuses on applying the second law to determine if the reaction is spontaneous given the conditions of the system that it is occurring in.

Introductory chemistry is very broad in order to give a strong foundation for other related subjects. There is a lot of information to be covered and it is best to be familiar with all of these concepts so when they are expanded upon, it is not your first time seeing the material.