Separating Blood

About one million donations of blood are made in Australia each year. Some of the donations are given to people who have lost blood during surgery, accidents or disasters. Blood is also given to people during the treatment of many diseases, including cancer. These people need to be given a regular supply of blood.

Blood is a life-giving mixture. It can be separated into four parts: plasma, a clear, yellowish liquid; red blood cells, which carry oxygen; white blood cells, which fight disease; and platelets, which clot blood. Because each part of the blood has a special job to do in our bodies, different problems can be treated with different parts of the blood. In Australia, blood is collected and separated by the Australian Red Cross Blood Service. Separation allows doctors to treat a larger number of patients and save many lives. The blood cells and platelets are separated from blood donations by spinning in a refrigerated centrifuge. Further centrifuging separates the platelets and different types of blood cells.

Blood type	Percentage of population	Most useful donations	Main uses
AB	3%	Plasma	AB plasma can be given to any blood type
A	38%	Whole blood, plasma or platelets	Common blood type so high demand for these products
B	10%	Plasma	Particularly useful for people with blood diseases, severe burns or trauma
O−	9%	Whole blood or platelets	All products can be given to any blood type
O+	40%	Whole blood or platelets	Most common blood type; high demand for these products

What's in a fizzy drink?

The ‘fizz’ in fizzy drinks is the carbon dioxide gas that is dissolved in the flavoured liquid. Carbon dioxide is pumped into bottles or cans at high pressure. The bottles and cans are then sealed to keep the carbon dioxide dissolved in the water. When you open the container, the pressure is reduced and the carbon dioxide bubbles out.

Like most substances, fizzy drinks are mixtures of other substances. If you look at the label on a bottle or can of soft drink, you will see that, as well as carbon dioxide, it also contains sugar, food colouring, flavouring and preservative. Preservatives stop the substances in soft drinks from going off. Flavourings are added to make the drink taste more pleasant and food colouring is added to make the drink look more attractive.

Separating Solutions

Distillation

In the laboratory, pure water is produced by a process called distillation. Tap water is poured into the boiling flask (see the diagram above right) and heated to the boiling temperature for water, 100 °C. The water boils, evaporates and becomes steam. The steam travels along the water condenser. The steam inside the condenser is cooled to below 100 °C and condenses to form liquid water. The condenser is kept cool by running cold water through its outer jacket. The pure water collected in the conical flask is called the distillate and can be rightly labelled distilled water. The impurities in the water are left behind in the boiling flask. Distillation can be used to separate pure water from sea water. It can also be used to separate a mixture of two liquids as long as they boil at different temperatures.

Harry's Lab

Separating Blood

What's in a fizzy drink?

Separating Solutions

Distillation

Evaporation

Osmosis

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