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Isobel Gibson

March 7th, 2023

Three everyday situations and techniques used to separate mixtures


 * 1) Evaporation or boiling

This technique is used when a dissolved component needs to be recovered from a solution. For example, salt is extracted from seawater by evaporating the water. Evaporation relies on the different substances in a mixture having different boiling points. The mixture can be left out in the open (or put in an oven or on a hot plate) and the component with the lowest boiling point will evaporate leaving the other substance (or substances) behind.

For example

•Clothes drying in the dryer or on the washing line.

• Evaporating water to retrieve salt or sugar

2) FILTRATION

Filtering, sieving and straining

These separation techniques rely on the differences in size of the particles of the substances that make up the mixture. The effectiveness of separating a mixture by filtering (or sieving or straining) depends on the size of the holes in the filter (or sieve or strainer) compared to the size of the particles being separated. The important thing to remember is that the holes in the filter must be smaller in size than the particles of the solid substance being separated.

The term ‘filtering’ is generally used when the mixture contains a solid and a liquid, for example sand and water. When a sieve is used, the process is usually referred to as sieving. For example, a mixture of sand and gravel is separated using a sieve and works because the gravel particles are much larger than the sand particles. When a strainer is used the process is referred to as straining. For example, straining the spaghetti from the water after cooking.

There are many practical examples of separating mixtures by filtration.

• using a tea strainer or tea bag

• the filter in vacuum cleaner allows the air to pass through but not the dust and

other substances

• sieving flour to remove any lumps.

• Using a jug with a filter so water from the tap can be filtered for drinking.

• Using a coffee filter for filtering coffee.

• Using a tea strainer or tea bag.

• Filters in pools, air conditioners, vacuum cleaners and car engine

3) HANDPICKING

Handpicking is a very simple method of separation. If we give you a bucket full of mangoes and apples and ask you to separate them, then which method of separation will you use? You will start picking out one kind of fruit, either mango or apple. In this way, you will separate one from another. The separation technique which you are using here is handpicking.

This method involves simply picking out all the unwanted substances by hand and separating them from useful ones. The separated substances may be an impurity that has to be thrown away or maybe that both the separated substances are useful. For example – if you separate black grapes from green ones from a mixture of the two.