Properties of matter

Subject classification: this is a chemistry resource.

Solid, Liquid, Gas, Plasma

On a macroscopic level, gases are notable because of their ability to expand to the size and shape of a container. In addition, gases belong to the only state of matter that is governed by universal laws.

There are a few standard variables that are characteristic of all gases:

${\displaystyle \ p}$ is the pressure (N/m²)

${\displaystyle \ V}$ is the volume (L)

${\displaystyle \ n}$ is the number of moles of gas

${\displaystyle \ R}$ is the gas constant 8.314472 Joules/mol*K

${\displaystyle \ T}$ is the temperature in kelvin (K)

${\displaystyle \ a'}$ is the measure of attraction between the particles

${\displaystyle \ b'}$ is the space enclosed in one particle

${\displaystyle \ k}$ is Boltzmann's Constant, equal to 1.380650524×10²³ joule/kelvin

${\displaystyle \ pV=nRT}$

There are 4 gas laws that, when combined, yield the Ideal Gas Law (often pronounced "Pivnert"). The Ideal Gas Law assumes that particles have no attractions to each other (they do in actuality) and that particles of a mass are infinitely small (they aren't). However, the ideal gas law is accurate for all gases at high temperatures and low pressures. The only times when it becomes highly inaccurate are near the boiling and sublimation points of gases.

${\displaystyle {\frac {V_{1}}{T_{1}}}={\frac {V_{2}}{T_{2}}}\qquad \mathrm {or} \qquad {\frac {V_{2}}{V_{1}}}={\frac {T_{2}}{T_{1}}}\qquad \mathrm {or} \qquad V_{1}T_{2}=V_{2}T_{1}}$

This is used to determine the effects of a change in temperature on the volume of a gas at constant pressure and vice versa.

${\displaystyle \qquad \qquad {p_{1}}{V_{1}}={p_{2}}{V_{2}}}$

This law is used to determine the effects of a change in pressure on the volume of an ideal gas if temperature is constant and vice versa.

${\displaystyle {\frac {p_{1}}{T_{1}}}={\frac {p_{2}}{T_{2}}}}$

This law is used to calculate the effects of temperature on pressure, and vice versa. Note that there is no known way to increase pressure while keeping volume and number of moles constant besides simply raising the temperature. Additionally, note that if pressure were to suddenly drop, the temperature would also drop. This is the mechanism by which refrigerators operate.

Any two gases with the same volume at the same temperature and pressure contain the same number of particles. At 273.15 K and 101.3 kPa, this works out to approximately 22.4 litres.

${\displaystyle \left(p+{\frac {a'}{V^{2}}}\right)\left(V-b'\right)=kT}$

The van der Waals equation takes into account the fact that particles of a gas do actually take up space (i.e., at 0 kelvins they would still have a volume) and that particles of a gas are attracted to each other by dipole-dipole forces, London dispersion forces and van der Waals forces.

Organic compounds always contain carbon-hydrogen bonds, i.e., at least one carbon is bonded to at least one hydrogen. Naming conventions are determined by IUPAC, the International Union of Pure and Applied Chemistry. For more information, see Nomenclature.

Inorganic compounds are those which contain no hydrogen-carbon covalent bonds. Two major types exist: Ionic and Network Covalent. Ionic compounds are based on positive ions (cations), normally metal ions, attracted to negative ions (anions) by electromagnetic forces. The vast majority of ionic compounds are solids, although research into liquid ionic compounds looks promising. Ionic compounds are sometimes soluble in water, but not always. Network covalent compounds are those which have molecules that are infinitely repeatable in all directions. Atoms are bonded by shared electrons and are not charged. Examples include diamonds, graphite, and quartz (silicon dioxide).

For more info, see Inorganic Chemistry