# Gases --- **Gases** are a state of [[matter]] that have a relatively high [[energy]]. Substances in gas form take on the shape of the containor and also compress or expand to fully take up the container. Some [[element|elements]] are found naturally in gaseous form, and some of these gasses are particularly useful, like the non-reactive [[element|noble gases]]. Gases that are made up of more than one type of gas are subject to [[partial pressure|Dalton's law of partial pressures]]. ## Gas laws The **gas laws** are equations that can be used to determine the properties or behaviors of gasses. There are four main values that are important when discussing gasses: pressure (P), volume(V), amount of gas(n) and temperature(T). For laws pertaining to mixed gases, or gasses in solution see: [[partial pressure]] ### Boyle's Law **Boyle's law** states that when temperature and amount of gas remains constant there is an inverse correlation between volume and pressure. Essentially, as one changes, the other changes the other direction. $ P_1V_1=P_2V_2 $ It can also be expressed as "volume is inversely proportional to pressure" ($V\propto\frac{1}{P}$), or even "pressure multiplied by volume is equal to some constant, *k*" ($PV=k$). ### Charles' Law **Charle's Law** states that when the pressure and amount of gas remain constant, there is a positive correlation between volume and temperature. Essentially, as one changes, the other changes in the same direction. $ \frac{V_1}{T_1}=\frac{V_2}{T_2} $ It can also be expressed "volume is directly proportional to temperature" ($V\propto T$), or "volume equals some constant, y, multiplied by temperature" ($V=yT$) ### Avogadro's Law **Avogadro law** states that when temperature and pressure are constant, equal volumes of any gas contain the same number of molecules. Essentially, the more atoms of a gas there are, the volume increases, and vice versa. $ \frac{V_1}{n_1}=\frac{V_2}{n_2} $ It can also be expressed as "the volume of a gas is directly proportional to the number of [[mole|moles]] present in the sample" ($V\propto n$), or "volume equals some constant, *k*, multiplied by amount of gas" ($V=kn$) ### Ideal Gas Law The **ideal gas law** is the combination of all three gas laws, using the gas constant **R**. To derive it first you combine the three gas laws as they are proportional to V: $ V\propto \frac{nT}{P} $ Then we can replace the "∝" with the constant R: $ V=\frac{RnT}{P} $ Then tidy it up a little: $ PV=nRT $ Using this gas law you can calculate an unknown value pretty accurately, but it does not perfecty measure gases in the real world. The ideal gas law assumes the following: 1. The particles of the gas do not occupy any space 2. The particles of the gas move in a constant, random, straight-line 3. There is no force between the gas particles, they only collide with the sides of the container an each oher ___