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//Chemistry : Bromine - What it is, how to extract it, what it’s used for

• Bromine is a halogen.
• It can oxidise iodine, but is oxidised by chlorine and fluorine.
• Adding chlorine to a bromide solution causes a redox reaction - the chlorine oxidises the bromide ions, taking their electrons and causing them to become bromine atoms. 
• The bromine atoms are displace and they are seperated from the bromide compound. The chlorine changes into chloride ions.
• The chloride ions take the bromine’s place and from a chloride compound.

On an industrial scale, it’s harder to extract bromine in this way. Instead there is a more complex process:

1. Partially evaporate acidified sea water is warmed. (Sea water is slightly alkaline so this lowers the pH - sulphuric acid is used - as chlorine and bromine react better with water at higher pH levels.)
2. Chlorine is added. This is to displace bromine from the bromide ions in the sea water.
3. As bromine is very volatile, it evaporates and gives off bromine and water vapours when steam is blown through the reaction chamber.
4. The vapours condense into two immiscible layers.
5. The denser bromine layer is run off of the water layer above it. 
6. This impure bromine is distilled and dried.

In addition, bromine has several uses once it has been distilled and dried. Bromine is used in the production of analgesics and sedatives. Silver bromide is also used in camera films.

//Electron Subshells//

• There are 4 types of subshell : s, p, d, f.
• Shell 1 contains one s subshell. It can hold 2 electrons.
• Shell 2 contains one s, one p subshell. The p can hold 6 electrons.
• Shell 3 contains s, p, and d. The d can hold 10 electrons.
• Shell 4 onwards contains s, p, d and f. The f can hold 14 electrons.
• 3p and 4s overlap due to electron shells becoming closer together as you travel further away from the nucleus of an atom.
• A subshell is known as an orbital - this is the shape of the space where there is the highest probability of an electron being found in an atom.

(image from http://chemistry.compendiarious.net)

// Human Digestive System (Part One)//

• The digestive system consists of the alimentary canal, or gut, which is a long tube from mouth to anus. It is about 9 metres long.
• The mouth conducts mechanical digestion with the teeth and tongue to form a bolus, which is swallowed down the oesophagus via peristalsis (rhythmic contractions of the circular and longitudinal muscles in the gut wall). Chewing provides a larger surface area for enzymes to act upon, and also breaks the food down into smaller molecules.
• The stomach wall releases gastric juices, hydrochloric acid and receives bile from the liver (via the bile duct) to chemically digest the food. Enzymes in gastric juice break down larger polypeptides into smaller dipeptides and monopeptides.

(diagram from wikipedia.org)

//Iodine//

• Iodine (I) is an element in Group 7, making it one of the halogens (along with Cl, F, At and Br). 
• It has an atomic number of 53 (number of protons).
• Iodine is diatomic - it is usually written as I_2.
• Iodine is a solid at room temperature, dark purple in colour with a crystalline structure.
• When exposed to heat, iodine sublimes- it changes state from a solid straight to a gas without becoming a liquid. This suggests that iodine has relatively weak intermolecular bonds - if it sublimes then this shows that relatively small amounts of energy are needed to break these bonds. 
• This sublimation produces a purple vapour, that can combine with air to form acid which will corrode the lungs if inhaled.
• Iodine is relatively insoluble in water, as it forms non-polar molecules, but it does dissolve quite easily in organic solvents such as hexane. (This is true for the halogens in general.)
• Iodine has a variety of oxidation states.
• Iodine is used in solution to test for starch. 

(Photo from wikipedia.org)