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**Gas Properties and Characteristics**:
– Elemental gases include hydrogen, nitrogen, oxygen, fluorine, and chlorine.
– Gas particles have weak intermolecular bonds, low density, and viscosity.
– Gases spread out to homogeneously distribute themselves in a container.
– Pressure, volume, number of particles, and temperature describe gas properties.
– Boyle’s law (PV=k) and mathematical tools like Euler equations analyze gas behavior.

**Gas Behavior and Kinetic Theory**:
– Gas particles move freely and randomly, changing direction upon collisions.
– Kinetic theory relates macroscopic properties to kinetic energy per molecule.
– Pressure results from microscopic particle collisions, with temperature quantifying particle motion.
– Brownian motion describes random movement of gas particles in a fluid.
– Van der Waals forces play a key role in determining physical properties of gases.

**Ideal vs. Real Gases**:
– The ideal gas law equation is PV=nRT, suitable for engineering applications.
– Real gases deviate from ideal behavior at extreme pressures and temperatures.
– Real gas effects include compressibility variations, variable heat capacity, and Van der Waals forces.
– Permanent gases have critical temperatures below human-habitable ranges.
– Boyle’s Law, Charles’s Law, Gay-Lussac’s Law, and Avogadro’s Law are fundamental gas laws.

**Gas Laws and Equations**:
– Boyle’s Law establishes the inverse relationship between pressure and volume.
– Dalton’s Law of partial pressures states the total pressure of a gas mixture.
– Compressibility factor adjusts the ideal gas equation for real gases.
– The Reynolds number relates inertial forces to viscous forces in fluid dynamics.
– Viscosity is a measure of molecular stickiness in fluids, essential for boundary layers.

**Historical and Special Topics**:
– The term ‘gas’ was first used by Jan Baptist van Helmont in the 17th century.
– Alternative etymological connections include Ancient Greek and German words.
– Advanced math is used for safety calculations in extreme gas conditions.
– Specific volume, density, and microscopic view of gases are vital concepts.
– Turbulence in fluid dynamics involves chaotic property changes, seen in weather patterns.

Gas (Wikipedia)

Gas is one of the four fundamental states of matter. The others are solid, liquid, and plasma. A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide). A gas mixture, such as air, contains a variety of pure gases. What distinguishes gases from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer.

Drifting smoke particles indicate the movement of the surrounding gas.

The gaseous state of matter occurs between the liquid and plasma states, the latter of which provides the upper-temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention. High-density atomic gases super-cooled to very low temperatures are classified by their statistical behavior as either Bose gases or Fermi gases. For a comprehensive listing of these exotic states of matter, see list of states of matter.

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