Separating mixtures


Distillation is a method used to separate a mixture of liquids according to their boiling temperatures. The liquid is vapourised at a certain temperature, the vapour collected and then condensed to form a liquid again. The liquid collected during this process is called the distillate while the residue is the mixture that remains in the original container. The wine bottle on the right contains 14% alcohol. For every 100 mls of wine 14 mls of alcohol are present. Ethanol boils at 85.5oC where as water boils at 100oC.

We can separate the ethanol from the water by using a distillation unit like the one shown on the left. The wine is placed in a flask and heated to 86oC. The ethanol evaporates, escapes from the water and is trapped in the condensing tube where it is converted back into a liquid.

Scan the image on the left to identify the components of the distilling unit.

Click to see an animation of how this unit works.

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Pure ethanol is a very flammable liquid and is often used in racing cars. Ethanol burns with a clear flame and is very difficult to detect as shown in the picture on the right. Click to see a 120kb video of how the ethanol collected from this procedure burns with a clear flame. Ethanol also acts as a local anesthetic which is why swirling Vodka or Ouzo on a very sensitive tooth relieves the pain.

Distillation is used to make brandy from wine. The wine is gently heated and the alcohol and some of the flavours present in the wine evaporate and are condensed. Some of the water is removed and the resulting mixture has a greater concentration of alcohol than the original wine.
Liebig condenser Distilling flask Collecting flask Heat source Water outlet Water inlet