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."
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.
Later in the day, their Mama takes them to the fields where they observe bundles of harvested wheat stalks lying in the fields. A group of farmers are beating the stalks on a large wooden log. 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.
The separated grains get mixed with piles of husk. Valli wonders, "Will the farmers handpick the grains to remove them from so much husk? How much time will the farmers take to separate these?"
- •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.
Traditionally, a soop (bamboo tray) is used for separating heavier and lighter components of a mixture (Fig. 9.3). Malli and Valli observe a farmer standing on a raised platform, moving the bamboo tray which contains threshed wheat grains in the direction of air or wind (Fig. 9.4). The lighter husk is blown away while the heavier grains fall straight down.
This method of separating heavier and lighter components of a mixture by wind or by blowing air is called winnowing. Have you seen any similar kind of activity being done at your home?
Next, Malli and Valli board a train to Ahmedabad to visit their father's friend Ghanshyam bhai. Before leaving, Valli requests her Mami to prepare meethi puri (sweet Indian bread made from wheat flour) for their journey.
Sieving allows the fine flour particles to pass through the holes of the sieve as shown in Fig. 9.5. The bigger particles such as bran and small stones remain on the sieve. Carefully observe a sieve. Are all the holes of the sieve the same size? Will sieving work if the holes of the sieve are larger than the substances? Sieving is used when components of a solid–solid mixture have different sizes.
Upon reaching Ahmedabad, they visit Sabarmati Ashram along with Ghanshyam bhai where they learn about the Namak Satyagrah (Dandi March). Malli asks, "Where is namak (common salt) obtained from?" "From seawater," replies Ghanshyam bhai.
Seawater is a mixture of salts and some other substances dissolved in water. To obtain salt, the seawater is kept in shallow pits and exposed to sunlight and air. In a few days, the water evaporates completely, leaving behind the solid mixture (Fig. 9.6). Common salt is then obtained from this mixture by further purification.
- •Have you ever observed white patches on the dark coloured clothes you wear during hot summers? How are these patches formed?
- •Take a bowl or any container and fill it half with water.
- •Add 2–3 teaspoons of salt into it and stir till the salt dissolves to form a solution.
- •Take a small piece of black or dark coloured thick paper and spread a few drops of the salt solution on it (Fig. 9.7a).
- •You can also create any art of your choice with this salt solution.
- •Allow it to dry and then observe it (Fig. 9.7b and Fig. 9.7c).
- •Do you observe some patches on the paper? What do you think is left on the paper? You can feel the presence of salt by touching the paper. Where has the water disappeared?
Fig. 9.7: A few drops of salt solution spread on thick black paper
| (a) Before drying | (b) After drying | (c) Art created |
|---|---|---|
| A dark wet patch on black paper. | A white crystalline patch on black paper. | A fish shape made of white salt crystals on black paper. |
- •This activity may be demonstrated by the teacher.
- •Take some salt solution (prepared in Activity 9.2) in a china dish. If a china dish is not available, another suitable vessel may be used.
- •⚠️ Caution: Be careful while heating the china dish.
- •Heat and let the water boil away as shown in Fig. 9.8.
- •Allow the china dish to cool.
- •What do you observe? What is left in the china dish?
- •Did you get the salt back? You can feel the presence of salt in the china dish by touching it with your fingers.
It is now time to visit Dada and Dadi (paternal grandparents) residing in Puducherry. Malli and Valli meet their old neighbourhood friend, Balan. It is Dadi's tea time.
This process of separating tea leaves from tea is called filtration. Balan asks Malli if he could use a tea strainer to filter muddy water. Dada says: "Also, try to filter the muddy water through a piece of cloth and observe the difference. In a piece of cloth, there are very small holes or pores between the woven threads. These pores in the cloth can be used as a filter." If the water is still muddy, a filter paper with very fine pores can be used.
- •Try to fold the filter paper yourself and make a cone as shown in Fig. 9.10 (one fold → two folds → cone shape).
- •Place it inside a funnel kept on a conical flask and pour muddy water into it (Fig. 9.11).
- •What do you observe? Do the mud particles pass through the filter paper?
- •The water coming from the funnel will be collected in the conical flask.
- •You will get mud as a residue on the filter paper and clear water as filtrate in the conical flask.
- •Valli goes for a nature walk with her Dadi and collects some water from a pond in a container. She observes some unwanted substances in it.
- •Design and create a working model of water filter using low-cost materials.
The train reaches Bhopal in Madhya Pradesh. On their way to Maasi's home, they drink chhach (buttermilk) in a dhaba (roadside eatery). Malli asks the shopkeeper about a big painting on the wall showing a lady performing the process of churning curd using a big mathni (churner) to separate butter. In this process, the butter being lighter floats at the top, while the buttermilk is left behind.
On their arrival at their Bua's (paternal aunt's) house in Shillong, they notice a carpenter making a wooden door. He accidentally drops a few iron nails in the sawdust. The carpenter starts handpicking the iron nails. The children get a magnet from their Bua and ask the carpenter to move the magnet through the sawdust. All the nails get attracted to it (Fig. 9.12).
Malli and Valli had delightful holidays and the 'Bharat ki Yatra' (tour of India) filled with fun will be an everlasting memory for them. They not only enjoyed exploring different regions of India but also gained a lot of knowledge about various methods of separation of substances.
- •Write the following phrases on small slips of paper: (1) Separating small stones from pulses, (2) Churning curd to obtain butter, (3) Taking out green chillies from cooked dalia or poha, (4) Taking out seeds from watermelon, (5) Sorting piles of sawdust and iron nails, (6) Picking marigold flowers from a heap, (7) Separating pebbles from sand, (8) Separating coconut pieces from rice flour, (9) Separating oil from water, (10) Separating salt from salt solution.
- •Take two baskets: • Basket 1: To remove any one of the components that is not useful • Basket 2: To separate two different but useful components
- •Form two teams and see who will get the maximum correct entries.
- •This activity helps in assessing your understanding as to why we separate substances.
Keywords
- 1Handpicking is used for separating solid materials on the basis of differences in size, colour and shape from a mixture.
- 2The process in which the stalks are beaten to separate grains from them is called threshing.
- 3The method of separating lighter husk from heavier grains by wind or blowing air is called winnowing.
- 4The process of separating solids from a mixture based on variations in particle size using a sieve is called sieving.
- 5Evaporation is the process in which a liquid gets converted into its vapour. It can be used to separate a solid dissolved in a liquid.
- 6The process of settling down of heavier insoluble component at the bottom of a liquid is called sedimentation. When the liquid is removed by tilting the vessel, the process is called decantation.
- 7Filtration can be used to separate insoluble solid components from a liquid.
- 8Churning is used to extract butter from curd.
- 9Separation of magnetic and non-magnetic substances by using a magnet is called magnetic separation.
- Fun with parents: We are proud of our Indian heritage. Under supervision of your elders, try to prepare some herbal remedies using various parts of plants. For example — tulsi kadha. Which methods of separation will you use while preparing herbal kadha?
- Stage play: Imagine you and your friend are Malli and Valli. Write dialogues of a play presenting their entire "Bharat ki Yatra", highlighting the different methods of separation of substances that they observed. Enact the play in your school assembly.
- Group activity: Observe and list separation methods you employed and noticed in your surroundings throughout a week. Explain the reasons behind using these methods and compile the ones you utilised or observed the most. Compare your observations with your group members.
- Be a stalwart of your community: Interview a ragpicker(s) and prepare a case study about the method(s) of separation he/she uses in his/her daily life.
- Be a reporter: (i) Gather newspaper clippings and articles related to various methods of separation implemented in your society. (ii) Conduct interviews with local farmers to explore the latest agricultural separation methods that they use.
- Think like a scientist: You are provided with a mixture of iron nails, sand, black pepper, stones, common salt and water. Which steps will you follow to separate each component? Hint: A mixture that has more than two components requires a combination of several methods of separation.
