Oxidation and Reduction

Oxidation is the gain of Oxygen and Reduction is the loss of Oxygen
The extraction of metals from their oxides is reduction.

Most metals corrode. The corroding of metals is called Rusting. Corrosion happens when the surface of the metal is changed by the reaction with Oxygen. When metals corrode the metal is oxidised.

The more reactive the metal, the more rapidly it corrodes. Metals with low reactivity are more resistant to oxidation and corrosion. For example, Gold does not corrode at all.

Biofuels

Biofuels are positive alternatives to fossil fuels. They are obtained from living organisms or organisms that have recently died. Wood and dried animal droppings have been used as fuels for hundreds of years.

• Ethanol is made by processing wheat, sugar cane or sugar beet. Ethanol can be mixed with petrol to be used in car engines as fuel. Helps reduce the demand for petrol and in turn saves crude oil supplies.

Advantages

• Biofuels are a renewable resource
• Reduce the amount of Carbon Dioxide human activity puts into the air

Disadvantages

• Lots of crops to grow biofuel. Lots of farmland used for biofuels instead of food
• Excess land with trees may be burnt down to make space for biofuel farms.

Ores

Some metals are found naturally in the Earth's crust. These are nonreactive metals such as Gold and Platinum.

Ores are rocks that contain enough of a compound to extract a metal for profit.

Extracting metals from their ores: (Extraction)

• Heating their compounds with carbon (Iron is extracted by heating Iron Oxide from Iron ore using carbon)
• Electrolysis of a molten compound (more expensive than heating with carbon due to cost of electricity - Aluminum)

The more reactive a metal is, the harder it is to extract. 

The more reactive metal is harder and more expensive to extract.

Electrolysis of Water

Nuclear submarines use Electrolysis to produce Oxygen for the crew when staying under water for months at a time.

If a direction current is passed through water, Hydrogen and Oxygen are given off at the electrodes.

The electrolysis of dilute Hydrochloric Acid produces hydrogen gas and chlorine gas.

To test for oxygen, light a splint but then blow it out so that the end of the splint is still glowing. Put the splint into the test tube. If the test tube has oxygen in it, the splint will relight into a flame again.

Hydrogen uses

• Rocket fuel

Oxygen Uses

• We all need to breathe Oxygen to live.
• In hospitals, patients with breathing problems are given extra Oxygen.
• Enclosed places such as nuclear submarines or spacecrafts - either carried in cylinders or made using Electrolysis.

The Importance of Chlorine

Sea water contains sodium chloride. If a direct current is passed through sea water, chlorine gas is produced at the electrodes.

Potential Problems:

• Sometimes gases can leak accidentally from a chemical factory, or a tanker.
• Chlorine is a toxic gas and if a leak occurred near a town, many people could be killed + injured.
• A leak of toxic gas could kill more people than an explosion.

Bleach is harmful to living things. It also reacts with many coloured substances, coverting them to colourless products. 

Symbol for Chlorine is CI

Symbol for the atom Chlorine is CI

The formula for Chlorine gas is CI2

Compounds that release Chlorine are well known for keeping water free from bacteria in public swimming pools.

Electroylsis

Electrolysis is the process where compounds are broken down into similar substances when an electric current is passed through them.

Hydrochloric acid is made by reacting hydrogen and chlorine together to form hydrogen chloride. 

You can test a gas to see if it is chlorine by holding a piece of damp blue litmus paper in the mouth of the tube. If the gas is chlorine the paper will turn red and then turn white, as it is bleached.

You can also test a gas to see if it is hydrogen by holding a lighted splint in the mouth of a test tube containing the gas. If the gas is hydrogen, the mixture of hydrogen and air in the tube will explode with a squeaky 'pop'.

          (Photo from http://www.sciencephoto.com/media/435714/enlarge)

Indigestion

Your stomach produces Hydrochloric acid in order to:

• Help Digestion
• Kill Bacteria

Bacteria could be on your food. Food in the stomach is broken down by digestive enzymes that need acidic conditions to work properly.

Too much Hydorochloric acid in the stomach can cause stomach pain (indigestion). It is called heartburn when the acid escapes from the top of the stomach which causes pain into the tube leading to the mouth although it has nothing to do with the heart.

Indigestion remedies
Medicines called Antacids can get rid of excess stomach acid. Antacids contain bases (substances that react with acids). The neutralisation reaction between an acid and a base produces water and a compound called a salt. Acid + Base ---> Salt + Water

Some bases are soluble. A base dissolved in water is called an Alkali.