Entropy

Not to be confused with Enthalpy.


Entropy is the degree of disorder.
Systems will move to a state of maximum disorder unless forced otherwise. (E.g. Tidying a room: If a room is not tidied periodically, it will eventually reach a state of optimum chaos)


exampli gratia, 
Diamond has a very ordered structure, so it's least disordered, so it has a low Entropy.

Gases don't have ordered structures, so they're most disordered, so they have a great Entropy.

Solids have the lower entropy.

Liquids have a medium entropy.

Gases have the greatest entropy.

Epsom Salts

Salts used by Victorians as a medical remedy. They're Magnesium Sulphates, made by bonding Magnesium Carbonate and Dilute Sulphuric Acid.

MgCO_{3 (s)} + H₂SO_{4 (aq)} --> MgSO_{4 (aq)} + CO_{2 (g)} + H₂O _(l)

Alternative Fuels

• Ethanol and Bio Diesel

E.g. From Sugar Canes via fermentation.

Pro - Some CO2 is captured and 'reused'.

Pro - Reduces the demand for fossil fuel.

Con - More expensive than fossil fuels.

Con - Plants are fragile.

Con - Ridiculous land needed to provide the amount of fuel required.

• LPG - Liquefied Petroleum Gas

60% Propane, 40% Butane

Pro - Less CO, NO, and unburnt fuels.

Pro - Cheaper as compared with common fossil fuels.

Con - Difficult to store.

Con - Greater evaporative emissions.

• Hydrogen

Can be consumed in two ways:

1- Via burning: Like common fossil fuels, producing some NOx and water.

2- Via fuel cells: taking place in a cell rather than an engine, producing pure electricity.

Pro - Little or no pollution.

Pro - Semi infinite source of energy.

Con - Difficult to manufacture and store.

*Can be obtained from water via electrolysis.

• Nuclear Energy

Produced via the breaking down of unstable nuclei.

Pro - Long life span.

Con - Expensive and difficult to build and manufacture.

Mass Spectrometry

Used to measure the atomic or molecular mass of different particles in a sample.

This is like totally awesome because chemists can demonstrate how badass they are by doing CSI stuff with it.

Now there are many different mechanisms in which Mass Spectrometry can be done through, but because you’re just a dim-witted student, you only need to know one. Funnily enough referred to as “Mass Spectrometers”.

Those things sound like they come from Star Wars, but really if you break them down, they’re just as complex as a toaster. Not that you, as a dim-witted student would know how a toaster works. Did you know that the adjusters on toaster are actually timers in minutes, not power levels which is the common misconception.

Breaking a Mass spectrometer down, you’d find three main parts,

An Ioniser, or if you’re feeling Fat and Patriotic, you could call it an Ionizer. All the same: The ioniser is where the sample goes after being injected from a sample inlet for it to get turned into ions, clue is in the name. This is done by bombarding the little stream of sample with electrons. ELECTRONS EVERYWHERE. Btw, if you put the word “Sea of electrons” you deserve to die, because that’s not acceptable A level Chemistry terminology, but since you’re a dim-witted student, the examiner might let you off.

General formulae for what happens in the ioniser zone of a mass spectrometer:

X_(g) + e^- à X⁺_(g)+ 2e^-

The Analyser, or if you’re a fat patriot, you might know it as the analyzer, is the second component in a Mass Spectrometer.

The crap thing about the analyser for a student is that there are so many different types of it. The one you should bear in mine is the one that measures time of flight of the ions. Basically, ions are accelerated using whatever method, usually a magnetic pulse, so that they’re all strolling with the same level of energy, in the same direction, and the fatter ions take longer than the skinny ions to cross a certain distance. This is called measuring the “Time of flight”.

After the ions go through the analyser, and get all analysed and so forth, they go into the Detector chamber, where ions are deteced by an ion detector. The detector produces a varying electric current depending on the ion it got hit with, and the “computer” registers this as a piece of data which eventually gets compiled into an Abundance/Charge graph, aka Mass Spectra!

Molecular shape structures - As far as an A level student needs to know.

Tetrahedral

(E.g. Methane CH4)

109 degrees apart.

Pyramidal

(E.g. Ammonia)

109 degrees apart.

Bent

(E.g. Water)

104 degrees apart.

Linear

(e.g. BeCl2)

180 degrees apart

Planar Triangular 

(E.g. BF3)

120 degrees apart, and two dimensional

Trigonal bipyramidal

(E.g. Phosphorus Pentachloride)

120, or 90 degrees apart

Octahedral

(E.g. Sulfur hexafluoride)

90 degrees apart on all planes.

Quick Guide to Molecule Shapes

A general example in Methane:

Where the firm lines resemble what lies on the 2D plane.

The dotted line resembles what lies backwards.

The Wedge resembles what lies forwards.

Making Methane actually look like this:

We use these denotations because molecules in real life are actually 3 Dimensional. 

n.b. Lone pairs are very important in atoms in molecules because they define what else the atom can bond with.