Separation Techniques
Sorting
The simplest way of separating mechanical mixtures is by sorting. Sorting is used when the two (or more) types of matter are in fairly large pieces. Sorting simply involves looking at the various parts and physically moving one or more of the parts into a different container. The parts of many mechanical mixtures, however, are in pieces that are too small to separate by sorting. For these mixtures, you have to look at other ways of separating the parts. This often involves finding a way in which the parts of the mixture are different from each other. Floating Floating is a separation technique in which a “lighter” component rises to the top of a liquid where it can be skimmed or poured off. Settling Settling is a separation technique in which a “heavier” component sinks to the bottom of a liquid, and the liquid can be poured off. Magnetism Some metals and alloys, such as iron and steel, are attracted to magnets. Other metals (for example, silver and aluminum) and most non-metals (for example, plastic and glass) are not attracted to magnets. If only one part of a mechanical mixture is attracted to magnets, a magnet can be used to separate that part from the rest of the heterogeneous mixture. Sieving Sieving is the process of passing a mechanical mixture through a sieve to separate out the larger pieces of matter. A sieve is a tool used to separate the components a mixture, with many visible holes that allow smaller solid pieces and liquids to pass through while blocking the larger solid pieces. Filtration Filtration is similar to sieving but it is used to remove tiny pieces of solids from a liquid or a gas. The holes through a filter are usually too small to see, so any solid pieces become trapped and cannot pass through. Distillation Distillation uses boiling to separate mixtures of liquid solutions. It takes into account that different substances in the mixture will have different boiling points. For example, if you heat salt water the water in the solution will boil before the salt. The water will then evaporate leaving the salt behind. If the steam from the water is collected it will turn back into liquid as it cools. This cooled water will be pure water without any salt. |