The method used to extract a given metal depends on how reactive concours de tee shirt mouillé it is: very reactive metals electrolysis less reactive metals - reduction, iron and steel rust when they uber voucher paris come into contact with water and oxygen: this is a form of corrosion.
It is easy to see that the aluminium has been oxidised.Aluminium does not rust (corrode) because its surface is protected by a natural layer of aluminium oxide which prevents the metal below from coming into contact with air and oxygen.A fairly common lab involves the reduction of copper(II) oxide by hydrogen.In the experiment below, the nail does not rust when air - containing oxygen - or water is not present: Calcium chloride absorbs water in the right-hand test tube.Unlike rust, which can flake off the surface of iron and steel objects, the layer of aluminium oxide does not flake off.It is also the loss of oxygen from a substance.
Metal oxides tend to be very stable compounds, and hydrogen, though it is flammable, is not terribly reactive stuff either at room temperature.
Take a look at the following thermite reaction : aluminium iron(III) oxide iron aluminium oxide.
We call this type of reaction a redox reaction.For example, magnesium is oxidised when it reacts with oxygen to form magnesium oxide: magnesium oxygen magnesium oxide 2Mg O2 2MgO, reduction is the gain of electrons by a substance.CeH2 CuO - H2O Cu, the activity/reactivity series of metals can be used to predict which metals will be reduced by hydrogen.Rusting is an oxidation reaction.CuO H2 Cu H2O, usually, oxidation and reduction take place at the same time in a reaction.Note that: the oxidising agent is the chemical that causes oxidation the reducing agent causes the other chemical to be reduced.The reaction is strongly exothermic; it can be thought of as a thermite reaction, so this isn't particularly surprising.