Separation Techniques: Handpicking and Sieving

Separation of Mixtures

• Handpicking is a method used to separate undesirable solid substances or impurities from useful solids by hand.
• Handpicking is used when the undesirable substances differ in shape, size, or color, and are present in small quantities.
• Examples of handpicking include removing stones, insects, and broken grains from rice and pulses before cooking.

Sieving

• Sieving is a method used to separate components of a mixture using a sieve.
• A sieve is a piece of mesh held in a frame, which allows fine particles to pass through while retaining bigger components.
• Sieves of different sizes are available for different purposes, such as sieving flour at home and separating stones and pebbles from sand at a construction site.

Threshing

• Threshing is the process of separating grains from stalks, used in agriculture after harvesting.
• Crops are cut from the field, sorted into bundles, and then threshed to separate the grains from the stalks.
• Threshing can be done by beating the stalks against a hard surface, using animals like bullocks to trample the stalks, or using machines.

Winnowing

• Winnowing is a method that uses wind to separate heavier components of a mixture from lighter ones.
• Farmers use winnowing to separate grains from their dry outer covering called husk, which is carried away by wind while the heavier grains fall near the place of winnowing.

Magnetic Separation

• Magnetic separation is a method that uses a magnet to separate a magnet substance from a non-magnetic substance in a mixture.