NCERT Book Class 6 Science Methods of Separation in Everyday Life PDF Download

Chapter 9: Methods of Separation in Everyday Life

Malli and his sister Valli are excited for their summer vacations. Their parents have planned a trip to visit their relatives and friends living across India. They always stay in touch with their relatives and friends. Do you also keep in touch with your loved ones?

Their first halt is at their Nani's (maternal grandmother's) house in Haryana. It is surrounded by large fields. Malli and Valli are fascinated by the variety of grains piled up in the courtyard. Their Mami (maternal aunt) and Mama (maternal uncle), along with other community members, are busy separating small stones and husk from the grains with their hands.

Malli and Valli are curious to know why this is being done. Their Nani notices their curiosity and explains, "We are removing these stones so that the grains are fit for cooking."

They go around the house to see the fields and the cattle. To keep them busy, Nani gives them a challenge of handpicking small stones from grains while keeping their eyes closed.

The method of picking by hand from a mixture (when two or more substances are mixed) such as small stones and husk from wheat and rice is called handpicking. It is done on the basis of differences in size, colour and shape of the particles. If the particles to be removed are present in small quantities and can easily be picked by hand, handpicking proves to be a convenient method.

[Figure 9.1: Handpicking, See in your textbook]

At lunch, Malli and Valli are served steaming hot vegetable pulao. While eating the pulao, Nani observes that Malli is separating whole black peppers from the pulao and is placing them aside on his plate. Valli playfully teases, "Wow! This is a handpicking method, nice one!" Nani tells them about the benefits of black pepper and encourages Malli to eat it.

Teacher's Note

Handpicking works best when the unwanted pieces are few and easy to spot - like black peppers in pulao or stones in rice. If almost everything in the mixture needs to be separated, handpicking becomes too slow. This is why farmers use other methods for large amounts of grain and husk.

Later in the day, their Mama takes them to the fields where they observe bundles of harvested wheat stalks lying in the fields. Some stalks are spread in the sun for drying. Both of them pick up a stalk each and notice numerous grains attached to it. A group of farmers are beating the stalks on a large wooden log. Curiously, Valli asks Mama, "Why are they doing this?" Mama explains, "They are beating the stalks to separate the grains" (Fig. 9.2). This process of separating grains from the stalks is known as threshing. Farmers work hard, yet they enjoy their work. From time to time, they sing folk songs while working.

[Figure 9.2: Threshing, See in your textbook]

The separated grains get mixed with piles of husk.

Valli whispers to Malli, "Will the farmers handpick the grains to remove them from so much husk?" She wonders, "How much time will the farmers take to separate these?"

Let us perform an activity to find out the answer to the questions raised by Valli.

Activity 9.1: Let us explore

• Take a handful of roasted peanuts and rub them between your palms. What happens?
• Is it possible to separate the removed skin and the peanuts?
• Now, try blowing it. What do you observe?

Which of these components - removed peanut skins or peanuts are blown away?

You observe that blowing air separates the heavier and the lighter components.

How do you think farmers separate so many grains from husk?

Traditionally, a soop (bamboo tray) is used for separating heavier and lighter components of a mixture (Fig. 9.3). Next day, their Nana takes them to the fields to show this process at work.

[Figure 9.3: Bamboo tray, See in your textbook]

Malli and Valli observe a farmer standing on a raised platform. The farmer is moving the bamboo tray which contains threshed wheat grains in the direction of air or wind (Fig. 9.4).

What do you infer from Fig. 9.4? Do both the components, wheat grains and husk, fall at the same place? Which of the two components get blown away? Can the wind separate the two components?

Teacher's Note

In winnowing, the key idea is that heavier objects (like grains) fall straight down while lighter ones (like husk) are pushed away by wind. The distance between where they land tells you the separation worked. You will see this pattern again with other mixtures - always think about which part is heavier and which is lighter when solving separation problems.

Key Points

• Handpicking is a method to separate unwanted particles from a mixture by picking them out by hand; it works well when there are only a few pieces to remove and they are easy to see.
• Threshing is the process of beating harvested grain stalks to separate the grains from the stalks.
• A soop or bamboo tray is used by farmers to separate grains from husk by moving the mixture in the direction of wind, which blows away the lighter husk while the heavier grains fall down.

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