View source for StudentWiki:StatesOfMatter

=States of Matter=

__TOC__


==General Principles==

===S.I. Units===

These basic quantities are vital within physical chemistry (and obviously just in general).<br />
It is also important to automatically understand the magitudes of various quantities. A chemist in general needs to know from mega- to femto- (or even atto-), i.e. the very small scale. A dirty physicist ( :P ) on the other hand needs to be aware of the macro scale of objects.
[[File:time scale of molecular interactions.png|thumb|400x400px|Time scale of molecular interactions.]]
{| class="wikitable" border="1" style="text-align: center"
|+ 
! Quantity !! Unit !! S.I. Unit !! Symbol
|-
| ''Mass''  || Kilogram || <span style="color:darkgreen">'''YES'''</span> || kg
|-
| ''Time'' || Seconds || <span style="color:darkgreen">'''YES'''</span> || s
|-
| ''Length'' || Meter || <span style="color:darkgreen">'''YES'''</span> || m
|-
| ''Electrical Potential'' || Volt || <span style="color:darkgreen">'''YES'''</span> || V
|-
| rowspan="2"|''Temperature'' || Kelvin || <span style="color:darkgreen">'''YES'''</span> || K
|-
| Degrees Celcius || <span style="color:red">'''NO'''</span> || °C
|-
| ''Moles'' || Mole<br />(6.02 x 10<sup>23</sup> molecules) || <span style="color:darkgreen">'''YES'''</span> || mol
|-
| ''Energy'' || Joules || <span style="color:darkgreen">'''YES'''</span> || J
|-
| ''Velocity'' || Meters/second || <span style="color:darkgreen">'''YES'''</span> || ms<sup>-1</sup>
|-
| ''Force'' || Newton || <span style="color:darkgreen">'''YES'''</span> || kgms<sup>-2</sup> (N)
|-
| rowspan="4"|''Pressure'' || Pascal || <span style="color:darkgreen">'''YES'''</span> ||  kgm<sup>-1</sup>s<sup>-2</sup> (Nm<sup>-2</sup> = Pa)
|-
| Bar || <span style="color:red">'''NO'''</span> || 1 bar = 10<sup>5</sup> Pa
|-
| Atmosphere || <span style="color:red">'''NO'''</span> || 1 atm = 1.01325 bar
|-
| Torr || <span style="color:red">'''NO'''</span> || 1 atm = 760 Torr (1 Torr = 1 mmHg)
|}

{| class="wikitable" border="1" style="text-align: center"
|+ 
! Magnitude (prefix) !! Mathematical Description
|-
| Mega  || 10<sup>6</sup>
|-
| Kilo || 10<sup>3</sup>
|-
| Centi || 10<sup>-2</sup>
|-
| Milli || 10<sup>-3</sup>
|-
| Micro || 10<sup>-6</sup>
|-
| Nano || 10<sup>-9</sup>
|-
| Pico || 10<sup>-12</sup>
|-
| Femto || 10<sup>-15</sup>
|-
| Atto || 10<sup>-18</sup>
|}

===Physical States===


{| class="wikitable" border="1" style="text-align: center"
|+ 
! State !! Description
|-
| GAS  || Distance travelled between “collisions” is large compared to the size of the particle. Particles are free to move past each other - they have unimpeded movement.
|-
| LIQUID || Distance travelled between “collisions” is comparable to the size of the particle. Particles are able to move past each other -  “jostling with movement”.
|-
| SOLID || Distance travelled between “collisions” is less than the size of the particle - continuous collisions. Particles are unable to move past each other - "jostling" but no movement.
|}

==Properties of Gases==

A gas, as described previously, is a substance whose molecules are free too move without hindrance. Like liquids, they are capable of filling any container they're in.<br />
The difference between a gas ana a liquid is simply that gas particles have a lot of space and time separating molecule collisions.<br />
This has led scientists to question what the properties of a perfect gas are.


===The Ideal Gas Law===

A perfect (or ideal) gas is in fact a hypothetical substance, for it does not take into account molecular interactions that real gases experience.<br />
The ideal gas law is one of the most important equations to know. It is given below:


<span style="font-size:150%"><math>PV = nRT</math></span>


where: 
* P = pressure (Pa)
* V = volume (m<sup>3</sup>)
* n = number of moles (mol)
* R = Universal Gas Constant (J mol<sup>-1</sup> K<sup>-1</sup>)
* T = temperature (Kelvin)


Its derivation can be summarised by the combination of three important observations:

{| class="wikitable" border="1" style="text-align: left"
|+ 
! Physical Law !! Observation !! Symbolic Description
|-
| '''''Charles' Law'''''  || At a constant pressure, the volume of a gas varies linearly with temperature. || <span style="font-size:150%"><math>V = constant \times T</math></span><br />at constant ''n'', ''T''
|-
| '''''Boyle's Law'''' || At a constant temperature, the pressure of a fixed amount of gas is inversely proportional to its volume. || <span style="font-size:150%"><math>P \times V = constant</math></span><br />at constant ''n'', ''V''
|-
| '''''Avogadro's Principle''''' || At a given pressure and temperature, equal volumes of gas contain the same number of molecules.<br />This introduces the concept of molar volume, i.e. the volume occupies by 1 mol of gas (V<sub>m</sub>). || <span style="font-size:150%"><math>V = constant \times n</math></span><br />at constant ''P'', ''T''<br /><span style="font-size:150%"><math>V_m = V \div n</math></span>
|}

Boyle's Law and Charles' Law are examples of limiting laws, in other words they can only be applies to a certain range - in this case from <math>p \rightarrow 0</math>