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What we have to do? Let us explore fabrics that are obtained from fibre. What d

What we have to do? Let us explore fabrics that are obtained from fibre. What do we need? A cotton duster (the one we use in kitchen) or mop cloth (used for floor moping), a needle, a pair of scissors. How do we proceed? 1. Spread the given piece of cloth on your table. 2. Cut the sides with the help of scissors to loosen the network of threads (Fig. 7.1). 3. Pull out the threads (yarn) from the cloth using a needle. (Fig. 7.2) 4. Keep the thread on the table and hold it at one end with your hand and scratch it with your nail and observe what happens. (Fig. 7.3 and Fig. 7.4) ACTIVITY 7 THEME 2 MATERIALS Figure 7.2 Pulling a thread from cloth Figure 7.3 Splitting the yarn into thin strands Figure 7.4 Yarn splits up into thin strands Figure 7.1 Cutting a piece of cloth Chapters.indd 25 26-04-2018 12:28:03 27/04/2018 Laboratory Manual 26 Note for the teacher • Make sure that students note that thread (yarn) of the cloth is not made of several strands in each case. What do we observe? It is observed that a thread (yarn) from the cloth splits into many strands/fibres on scratching with nail. What do we conclude? • Cloth is made of ______________________. • Yarn is made of several ______________________. • Strand of yarn is made of ______________________. Let us answer 1. What is the difference between yarn and strand? 2. What difference do you find between strand and fibre? 3. What is the ultimate constituent of cloth? What more can we do? • Take some other types of clothes and try to find out whether the yarn is made of single strand or many strands. Notes Chapters.indd 26 26-04-2018 12:28:03 27/04/2018 Materials 27 ACTIVITY 8 What we have to do? Classify the given materials on the basis of properties, such as hardness, solubility in water, floats in water, and transparency. What do we need? Wax, glass piece (with blunt edges), oil coated paper, sugar, green leaf, piece of coal, piece of wood, a coin, a piece of sponge, a container, water, spoon/glass rod, a sheet of white paper. How do we proceed? 1. Take the given materials one by one and observe the materials which are compressed on applying some pressure. Record your observations in a Table 8.1. 2. Take a container (like beaker, glass bowl, etc.) and fill it half with water. Add any given material and see whether it floats or sinks (Fig. 8.1). Now stir it with a spoon or glass rod and check if it is soluble or insoluble. Repeat the same steps with other materials also. Record your observations in the Table 8.1. 3. Take a strip of white paper and make a dark spot on it (Fig.8.2). Place the given materials one by one on the spot and observe its visibility whether you can see it clearly (Fig. 8.3), not clearly (Fig. 8.4) or not able to see it at all (Fig.8.5). Record your observations in the Table 8.1. Figure 8.1 Some objects flaot in water while others sink in it Figure 8.2 Paper with a dark spot Figure 8.3 Transparent material kept on dark spot Glass piece Paper Paper Oil coated paper Coin Figure 8.4 Translucent material kept on dark spot Figure 8.5 Opaque material kept on dark spot Chapters.indd 27 26-04-2018 12:28:03 27/04/2018 Laboratory Manual 28 What do we observe? Record all the observations in a Table 8.1. Table 8.1 Material Properties Hard/Soft Soluble/Insol- uble in water Sinks/Floats in water Transparency (transparent/ translucent/ opaque) Wax Glass piece Oil coated paper Sugar crystals Green leaf Coal Wood Coin Piece of sponge What do we conclude? • Materials which were easy to press are soft, such as wax, green leaf, sponge, etc. Materials which were difficult to press are hard, such as glass piece, sugar crystals, coin, coal and wood. • Materials which dissolved in water are called soluble materials, such as sugar. Materials which did not dissolve in water after stirring for a long are called insoluble materials, such as wax, glass piece, coin, coal, wood, green leaf, sponge etc. • Some materials float in water such as wax, wood and coal. Some materials sink in water, such as sugar, coin, glass piece. • Materials through which you can see clearly are transparent, such as glass piece. Materials through which you cannot see clearly are transluscent, such as oil coated paper.Materials through which you cannot see at all are opaque, such as coal, wood, sugar, wax, coin, and sponge. We conclude that materials are classified on the basis of their properties. Chapters.indd 28 26-04-2018 12:28:03 27/04/2018 Materials 29 Notes Let us answer 1. Mention any two properties of sugar that you have identified from this activity? 2. You are advised to drive your bicycle slowly on a foggy day. Why? 3. Find the odd one out from the following- Coal, wood, glass piece, sugar, candle. Justify your answer. What more can we do? • A project can be done on this concept. • Collect samples (at least 10) of different materials from your surroundings and classify them on the basis of their properties. Note for the teacher • Give freedom to students to explore and observe. • Kindly see that the materials used in the activity should not harm the user. • Students may take materials of their choice, but see that these materials show all the properties. Chapters.indd 29 26-04-2018 12:28:03 27/04/2018 Laboratory Manual 30 ACTIVITY 9 What we have to do? A mixture of iron, sand and common salt is provided to you. Separate the three components of this mixture. What do we need? A mixture of iron filings, sand and common salt, magnet, filter paper, funnel, two beakers, Petri plate, spoon/glass rod, heating device, tripod stand, wire gauze, a sheet of paper, match box. How do we proceed? Step I. Take a little amount of the given mixture of iron fillings, sand and common salt and keep it separately. Spread rest of the mixture on a sheet of paper or in a Petri plate (Fig. 9.1). Move a magnet over the surface of the mixture (Fig. 9.2). What happens? Do you find that iron fillings are removed from the mixture with the help of a magnet? Figure 9.1 Mixture of iron fillings, sand and common salt Figure 9.2 Iron fillings get attracted towards magent Step II. Take the remaining mixture from which iron filling have been removed in a beaker. Add sufficient amount of water to cover the mixture. Stir the contents of the beaker with a spoon/glass rod for some time. Chapters.indd 30 26-04-2018 12:28:04 27/04/2018 Materials 31 Filter the content with the help of a funnel and filter paper (Fig. 9.3). Record your observations. Step III. Heat the filterate obtained in step II using a heating device (Fig. 9.4). Heat the content till most of the water evaporates. FIg. 9.4 Heating a beaker containing salt water Figure 9.3 Filtration using a filter paper Glass rod Funnel with filter paper Tripod stand What do we observe? Step I. Iron fillings stick to the magnet and are thus separated. Step II. Sand remained undissolved in water and is separated by filtration. Step III. On heating the filtrate, water is evaporated and a white coloured substance (common salt) is left at the bottom of the beaker. Compare the separated components with the mixture you left aside. What do we conclude? • Magnetic substances like iron are separated by a magnet. • Substances which are insoluble in water (such as sand) can be separated by filteration. • Substances which are soluble in water (such as common salt) can be separated by evaporation. Chapters.indd 31 26-04-2018 12:28:04 27/04/2018 Laboratory Manual 32 Note for the teacher • You can make various types of mixtures and give opportunities to students to use different methods of separation based on their different properties. • Let the students discuss their findings in the class. Let us answer 1. Is there any method other than filtration by which we can separate sand from water? Explain. 2. Why does the filter paper permits the passage of the salt solution, whereas it retains the sand? 3. The filtrate containing salt when heated becomes dry. Where has the water gone and why? 4. Suggest a method to collect and use the water which disappears on boiling? What more can we do? • List the methods which are used at your home to separate components of mixtures. • Find out the ways used to purify water which is supplied at your home from water station. Notes Chapters.indd 32 26-04-2018 12:28:04 27/04/2018 Materials 33 ACTIVITY 10 What we have to do? Let us explore the nature of the following changes whether they can be reversed or not? (a) Disappearance of common salt on dissolving in water. (b) Cutting of potato What do we need? Common salt, water, glass tumbler, heating device, china dish, wire gauze, tripod stand, potato, knife. match uploads/Philosophie/ guide-research.pdf