Friday, 10 December 2010

Ionic Substances

Formed due to the loss or gain of electrons.

To make ions, an ionisation energy is required.

Ionisation energy is the amount of energy sufficient to remove an electron from the outermost shell of an atom.

The general equation for this is:
X (g) à Na+ (g) + -1 e

When an outermost shell has been exhausted, and you start taken electrons off the next shell (Which would be full), the ionisation energy increases significantly.

I.e. All element is group one, have a large 2nd ionisation energy. (Trying to remove the second electron)

Ions in solids

Ionic solids are giant lattices formed from ions being arranged in a regular way, and are held together by electrostatic bonds between oppositely charged ions.

This type of ionic bond is relatively strong and needs a large energy to overcome. For this reason, they have high melting and boiling points, so they tend to be solid at STP.

Ionic substances cannot conduct electricity when solid, but they can when in an aqueous solution.

The two ways of integrating H2O into an ionic substance:

1-      1- Water of crystallisation: Water sits in between ions of solids.
Example is Hydrated Copper Sulphate.
We include the water in the formulae. E.g. CuSO4.5H2O

2-      2- Hydration: Aka good old Dissolving.

Wednesday, 1 December 2010

Concentration Calculation

There are two methods to do concentration calculations, but to my concern as an Alevel chemist, only the following one is “Useful” because it includes Moles which can tell you a lot more about the substance and what its properties are as opposed to the singular sample you have in the experiment.

Concentration = Amount in moles ÷ Volume in cubic decimetres
1 decimetre cubed is equal to 1000 centimetres cubed!

Solutions in Geographical context

The following is mostly Geology and Biology and is of little interest to a real chemist.
The main two reasons behind the sea being salty are Hypothermal vents and Rain.

For some unmentioned reasons, chemistry A level students are required to recite the following:
The model for earth is that plate tectonics “float” on liquid mantle, and that they move due to currents caused by the constant change of mantle density resultant of nuclear shizzle radiating in the core.

So right, at the bottom of the ocean, those “trenches” allow the water to seep in. As the water seeps in, it flows against the molten mineral rocks, becoming a solution of those minerals and the water.

When the solution rises back to the ocean water, they cool down from the lethal 400 C’ to become black smokers ejecting sulphur and other minerals into the ocean, making a brilliant environment for bacteria to feed, colonise and grow.

The reason bacteria feed on this crap is because there’s no light for plants to photosynthesise at the bottom of the ocean so they have very different respiratory systems which were passed onto other life forms via evolution et cetera et cetera.

Then, as things are in the sea, big stuff eat smaller stuff. So the crabs would eat the bacteria for example.