Science: Class 6 — Chapter 9: Methods of Separation in Everyday Life

9.1 Handpicking

Concept of Handpicking

Mixture: A combination of two or more substances mixed together.
Handpicking: The method of manually separating components from a mixture based on differences in size, color, or shape.
Application: Convenient when the undesirable particles are present in small quantities (e.g., separating small stones and husk from wheat, rice, or pulses).

9.2 Threshing and Winnowing

Threshing

Threshing: The process of separating grains from harvested stalks by beating them against a hard surface (like a wooden log) or using machines.
Threshers: Modern machines that perform both threshing and winnowing simultaneously.

Winnowing

Winnowing: The method of separating heavier and lighter components of a mixture by wind or blowing air.
Application: Commonly used by farmers to separate lighter husk from heavier grains using a traditional bamboo tray called a soop.

9.3 Sieving

Sieving

Sieving: A separation method based on differences in particle size, where fine particles pass through the holes of a sieve while larger particles remain on it.
Application: Removing bran from wheat flour, or separating pebbles and stones from sand at construction sites.

9.4 Evaporation

Evaporation

Evaporation: The process in which a liquid converts into its vapor state. It is used to separate a soluble solid dissolved in a liquid.
Salt from Seawater: Seawater is kept in shallow pits exposed to sunlight. The water evaporates, leaving behind common salt, which is then purified.

9.5 Sedimentation, Decantation, and Filtration

Sedimentation and Decantation

Sedimentation: The process where heavier, insoluble solid particles in a liquid mixture settle down at the bottom.
Decantation: The process of gently pouring out the upper liquid layer without disturbing the settled sediment.
Application: Washing rice/pulses, or separating oil and water (since they form separate layers).

Filtration

Filtration: The process of separating insoluble solid components from a liquid using a filter (like cloth, filter paper, or a strainer).
Residue: The solid particles left behind on the filter (e.g., mud on filter paper).
Filtrate: The clear liquid that passes through the filter.
Alternative Filters: Cotton, charcoal, and sand can also act as filters depending on particle size.

9.6 Churning and Magnetic Separation

Churning

Churning: The process of vigorously shaking or spinning a liquid mixture to separate components of different densities.
Application: Churning curd using a mathni (churner) to extract lighter butter, which floats to the top, leaving buttermilk behind.

Magnetic Separation

Magnetic Separation: The method of separating magnetic substances (like iron) from non-magnetic substances using a magnet.
Application: Separating iron nails from sawdust, or using large electromagnets on cranes to separate scrap iron from industrial waste heaps.