Welcome dear students! Today we are going to learn about Materials Around Us from Class 6 Science. Let us begin with an ancient Sanskrit verse from the Rasaratnasamuchchaya. It says: उपादानं भवेतस्य (मृषायाः) मृत्तिका लोहमेव च। This tells us that the materials used to make the crucible, which is a vessel used to melt substances, are clay and iron. This reminds us that even long ago, people carefully chose materials for specific purposes.
In section six point one, we observe objects around us. Imagine Ghulan and Sheeta entering their new classroom after the summer break. Sheeta asks Ghulan what he brought to school. Ghulan shows his new notebook. Sheeta also has a new notebook and a pen. Their science teacher, Madam Vidya, enters and asks them to think about how these things are similar or different. She asks about their shapes, colours, how they feel when touched, and whether some are heavier than others. The answer is simple. All things are made up of some materials like paper, wood, cloth, glass, metal, plastic, and clay. Any substance that is used to create an object is referred to as material.
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Now let us do Activity six point one, titled Let us identify. I want you to look around your home or classroom. Make a list of objects you see and write the names of the materials they are made up of. You can create a simple table with two columns. The first column is I observe, and the second column is Materials they are made up of. For example, you might observe a wooden chair made of wood, or a glass bottle made of glass. Based on everyday observations, one can conclude that objects are made up of various materials.
Let us travel back in time. The earliest pottery found in the Indian subcontinent dates back to seven thousand to eight thousand years in the Ganga plains at Lahuradewa and in Baluchistan at Mehrgarh. About four thousand BCE onwards, the Sindhu Sarasvati civilisation developed techniques of wheel turned pottery production, pigmentation, application of protective or decorative coats called slips of multiple colours, and decorative painting. These techniques became further sophisticated during the Sindhu Sarasvati, also known as Harappan, Civilisation from twenty six hundred to nineteen hundred BCE. They created pottery with a bright red surface painted with black coloured designs displaying geometric patterns, and aquatic and terrestrial animals. The clay used for making pots, dishes, bowls and other items was carefully selected and cleaned, sieved, kneaded, turned over a wheel and finally baked in kilns. Baked clay is called terracotta. Pots were used for various purposes, from cooking to storage of food grains, oil, ghee, and so on. Some very large storage jars and other pottery items are exhibited at the National Museum in New Delhi.
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The textbook invites us to explore materials further. In section six point two, we learn how to group materials. Let us do Activity six point two, titled Let us group. Look at Figure six point one, which shows various everyday objects like a ball, a book, a spoon, a bottle, and a piece of cloth. Group these objects based on any common property, such as shape, colour, hardness, softness, shine, dullness or materials they are made up of. Which property did you use? Did your friends group objects based on similar properties? You must have noticed that an object can be made from different materials and some materials can be used to make more than one object. The method of arranging the objects into groups is called classification. Objects can be classified on the basis of a common property that they have. Similarly, we can classify materials based on certain properties.
Now let us think with Activity six point three. Look at Figure six point two, which shows a simple drawing of a tumbler with empty spaces around it for you to fill in. Think about what materials we can use to make a tumbler. Fill in the names of the materials in the spaces provided. Would it be a good idea to use paper like materials for making cooking utensils? Why cannot a tumbler made of cloth be used for storing water? The materials that are required to make a tumbler should be capable of holding water. What decides which material should be used for making an object? We choose a material to make an object depending on its properties and the purpose for which the object is to be used. We may use different materials for making different parts of an object. For example, a pen may be made up of different materials like plastic, metal and ink.
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Why are different materials used for making balls for various sports? Can a cricket ball be used to play tennis? Let us explore this with Activity six point four. Figure six point three illustrates a variety of balls that are of the same size but made up of different materials. You will see a tennis ball, a cricket ball, and a hand exercise ball. Take each ball and drop it from a fixed height. Note the height to which the ball bounces and record it in Table six point two. The table has two columns: Ball and Bounce, where you will write high, medium or low based on your own observation. After recording your results, identify the ball that achieves the highest bounce. Discuss in class other properties of sports balls, such as size, colour, texture and how high they bounce, and understand why balls are made up of specific materials for specific sports.
Now look at Figure six point four, which shows a collection of everyday items. Observe the figure and group the objects in as many different ways as possible. You might group them by shape, colour, or material. We have learnt that materials may be classified on the basis of their properties. In the kitchen, we store similar utensils together. A grocer keeps spices in one corner, pulses and grains in another. You can visit a chemist shop to see how medicines are arranged.
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In section six point three, we learn the different properties of materials. First, in six point three point one, we observe and identify appearance. Freshly cut wood, which is unpolished, has a distinct appearance, quite different from that of iron. Iron looks different from copper or aluminium. Yet, iron, copper and aluminium share similarities that make them different from wood. Let us do a sorting challenge. Collect small pieces of paper, cardboard, wood, chalk, copper wire, aluminium foil and any article made up of brass, bronze, steel, and so on. Look at the pieces. Do any shine when light falls on them? Observe their texture, whether rough or smooth, colour and other noticeable features, and record your observations. Group them based on appearance. Materials that typically have shiny surfaces are said to have a lustrous appearance. Such materials with lustre are usually metals. Examples of metals include iron, copper, zinc, aluminium, gold, and so on. However, some metals may lose their lustre and start to look dull or non lustrous due to the effect of air and moisture on them. As a result, we often notice the lustre only on their freshly cut surfaces. Non lustrous materials are those that do not have a shiny surface. Some examples of non lustrous materials are paper, wood, rubber, jute, and so on. Remember the old saying, all that glitters is not gold. Not all materials that shine are metals. Surfaces of some materials are made shiny by polishing or coating them with thin layers of plastic, wax or any other material which makes them look shiny. These materials may not be metals.
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Next, in six point three point two, we ask which materials are hard. When you press different objects or materials with your hands, some like stones may be hard to compress, while others like an eraser can be easily compressed. Take a metal key and use it to scratch the surface of a piece of wood, aluminium, stone, iron, candle, chalk and any other material or object. Can some materials be scratched more easily than others? Materials which can be compressed or scratched easily are soft, while other materials which are difficult to compress or scratch are hard. However, these properties are relative in nature. For example, rubber is harder than sponge but softer than iron.
Let us do Activity six point five, titled Let us observe. Hold the objects given in Table six point three with your hands. Feel whether the objects are hard or soft. Find out the materials they are made up of. Enter your observations in the table. The table lists objects like a brick, water bottle, pillow, tumbler, table, sweater, and any other object of your choice. The first row is already filled as an example: a brick is hard and made of baked clay. Fill in the rest based on your own observations. Compare your observations with friends and discuss. You have learnt that materials can have different properties, like lustre, hardness, softness and colour. After this activity, the textbook asks you to think: Are all lustrous materials metals?
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In six point three point three, we explore materials through which one can see or cannot see. Ghulan, Sheeta and Sara are playing hide and seek. Ghulan hides behind a wall, Sheeta hides behind a big tree, while Sara hides behind a frosted glass door which has a hazy surface. Sheeta's younger brother can see all of this happening through a glass window of his house. The materials, through which things can be seen clearly, are called transparent. Glass, water, air, cellophane paper, and so on, are some examples of transparent materials. Why did they choose these places? Do you think it would be possible for Sheeta's brother to see her and her friends through a closed wooden window of the house? There are many materials through which you are not able to see at all. These materials are called opaque. Wood, cardboard and metals are examples of opaque materials. The materials through which objects can be seen, but not clearly, are known as translucent. Butter paper and frosted glass are examples of translucent materials.
Look at Figure six point five. It shows four scenarios. The textbook asks you to identify and label the nature of materials used by Ghulan as A, Sheeta as B, Sara as C, and Sheeta's brother as D.
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Now let us do Activity six point six, titled Let us classify. Classify the following objects as transparent, translucent or opaque in Table six point four: glass tumbler, butter paper, eraser, frosted glass, wooden board, and window glass. Fill in the table based on your own observations. After this table, the textbook poses a question: Is water transparent? Can it be made opaque?
In six point three point four, we ask what is soluble in water and what is not. Ghulan was sweating and thirsty after playing. His mother mixed a spoonful of sugar, a pinch of salt and some lemon juice in a glass tumbler of water to make shikanji. Ghulan noticed that the salt and sugar disappeared after a while. Let us try Activity six point seven, titled Let us explore. Collect small amounts of sugar, salt, chalk powder, sand and sawdust. Take five glass tumblers and fill them about two third with water. Put a teaspoonful of sugar in the first glass tumbler, salt in the second one, chalk powder in the third, sand in the fourth and sawdust in the fifth glass tumbler. On stirring, predict what will happen in each case. Use a spoon to stir well the contents of each glass tumbler. Wait for a few minutes and watch what happens. Write down your observations in Table six point five. The table has columns for Material, Prediction, and Observation. Record whether each material will disappear or not disappear in water, and what actually happens after stirring.
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You might have noticed that some materials completely disappear when mixed in water. We say that these materials dissolve in water or, in other words, they are soluble in water. Some materials do not mix with water and do not disappear even after we stir them for a long time. These materials are insoluble in water. Water plays an important role in the functioning of our body because it can dissolve a large number of materials. The textbook then asks you to reflect: Does everything you put in water disappear?
Let us look at a special box titled Make your own ORS. ORS stands for Oral Rehydration Solution. It is used to treat dehydration due to diarrhoea or other illnesses. Ready made ORS packets are available in primary health centres and in the market. Each packet is dissolved in a litre of water before use. If these are not available, ORS can be prepared at home by mixing six teaspoons of sugar and half a teaspoon of common salt in one litre of boiled and cooled water.
The textbook then prompts you to explore: Do liquids like oil, vinegar and honey dissolve in water? Explore. What about the gases present in water? Some liquids get completely mixed with water. Some do not mix with water and form a separate layer when left undisturbed for some time. Similarly, some gases are soluble in water whereas others are not. For example, oxygen gas dissolves in water. It is very important for the survival of animals and plants that live in water.
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In six point three point five, we ask how heavy or light materials are. Let us do Activity six point eight, titled Let us measure. Take three identical paper cups or bowls. Fill each cup half with the provided materials. Fill one with water and mark it as A, second with sand and mark it as B, and the third with pebbles and mark it as C. Predict which one would be heavier and which one would be lighter. Weigh each cup using a balance, as shown in Figure six point seven which depicts a simple weighing balance with a cup on one pan. Record the readings. Compare the data. From this activity, we can say that any object which is heavier or lighter can be measured in terms of a property called mass. The one which is heavier has more mass and the one which is lighter has less mass. Weight is sometimes used in common language for mass as it is determined by weighing. You will learn more about mass and weight and their relation in higher classes.
In six point three point six, we learn about space and volume. Madam Vidya asks students to keep bags on seats. They cannot sit because bags have occupied that space. She gives two identical glass tumblers to students and asks them to pour water from their bottles. Figure six point eight shows two tumblers. Part A is half filled with water. Part B is fully filled with water. Why is the level different? Both tumblers have the same capacity. The water levels differ, indicating different amounts of water. The water in the first tumbler occupies less space, indicating that the volume of water in this tumbler is less than the water in the other tumbler. The space occupied by water represents its volume. A speech bubble in the textbook shares a student's thought: Why was I not able to transfer water from the jug into an empty water bottle completely? Now I know the reason behind it ... You may have noticed drinking water bottles of different sizes sold in the market, labelled 1 L, 500 mL, 200 mL, and so on. These indicate the volume of water in the bottles.
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Now you have become familiar with many properties of materials. However, all materials do not possess all these properties. The textbook asks: Are there any properties which can be shown by all materials? If yes, what are those? In section six point four, we learn what is matter. Mass and volume are the two properties that are possessed by all materials. Can we give a general name to anything that possesses these two properties? Anything that occupies space and has mass is called matter. The mass gives the quantity of matter, and the units to measure it are gram and kilogram. The space occupied by matter is its volume. The units to measure the volume are litre and millilitre.
The textbook then explains SI units. Kilogram is the unit of mass in the International System of Units. Kilogram is abbreviated in lower case as kg. There is no space between k and g in kg, and no full stop after the symbol, except at the end of a sentence. While writing the mass, always leave a space between the number and the unit. For example, if we have mass of 7 kg, it would be written as 7 kg and not as 7 kgs. Similarly, litre is abbreviated as capital L and millilitre as mL. There is no space between m and L in mL. For example, if you have 500 mL of water, it would be written as 500 mL. The SI unit for volume is cubic metre, abbreviated as m to the power three. The abbreviation is written with a superscript 3 to denote cubic metre. For example, if you have volume of 2 cubic metres, it would be written as 2 m to the power three. Always leave a space between number and the unit. 1 m to the power three equals 1000 L.
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Is air matter? Can all the materials around us be considered as different examples of matter? Discuss with your friends. For example, water is matter, sand and pebbles are matter and so is the cup. Materials are types of matter used in the creation or making of objects. We grouped materials on the basis of similarities or differences in their properties. Humans have been classifying things, rocks, plants and animals. Just like in the living world, classification of the non living world is also done on the basis of their properties. A student character in a speech bubble asks: Think it over! Can you think about what changes the invention of plastic brought to humans? Is it a boon or a bane?
A similar classification system existed in ancient India. Ayurveda, one of the Indian medical systems, too has a system of grouping things. The shloka precisely talks about the 20 properties (guna—ten pairs of opposite properties), which are used to describe all physical matter in Ayurveda. These properties are: guru meaning heavy versus laghu meaning light in weight; manda meaning slow versus tīkṣhṇa meaning quick or fast; hima meaning cold versus uṣhṇa meaning hot; snigdha meaning unctuous versus ruksha meaning dry; śhlakṣhaṇa meaning smooth versus khara meaning rough; sāndra meaning solid versus drava meaning liquid; mṛidu meaning soft versus kathina meaning hard; sthira meaning stable versus khāla meaning moving or unstable; sūkṣhma meaning subtle or small versus sthūla meaning big or gross; and viśhada meaning non slimy versus picchhila meaning slimy.
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Let us review the keywords from this chapter: Classification, Non-lustrous, Classify, Hard, Opaque, Explore, Insoluble, Soft, Identify, Lustrous, Soluble, Observe, Mass, Translucent, Predict, Material, Transparent, Record, Matter, and Volume.
Here is the chapter summary. Objects are made from a large variety of materials. An object can be made up of a single material or a combination of different materials. We can use different materials to make objects with similar functions. The method of arranging objects into groups is called classification. Materials possess different properties which determine their use. Materials are grouped or classified based on their similarities or differences in their properties. Materials can be grouped based on appearance, such as lustrous or non lustrous and based on the feel, such as hard or soft. Materials are grouped as transparent, translucent or opaque depending on how much we can see through them. Some materials are soluble in water, while others remain insoluble. Anything that occupies space and has mass is called matter. The space occupied by matter is its volume. Mass quantifies the amount of matter present in an object.
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Let us play game one, find the companion. Link the following words by putting arrows between words that have a connection: Iron, Transparent, Copper, Bottle, Plastic, Lustrous, Wood, Opaque, Glass. Try to match them based on their properties.
Let us play game two, win the word hub. The words from the chapter like lustrous, non lustrous, soluble, insoluble, hard, soft, matter, mass, transparent, opaque, volume and translucent are picked up. Students should randomly choose nine words from the given list and write them in a grid. Then, the facilitator either reads the definition of a word or the word itself randomly from the given list. The learners have to tick if the particular word is there in the grid. Whoever finishes ticking off all nine words first will shout out Hurray! That person will be the winner if his or her words are marked correctly.
Now let us enhance our learning by working through the exercises. Exercise one asks you to visit your kitchen and observe how your parents have organised various edibles. Can you suggest a better sorting method? Write it in your notebook.
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Exercise two asks you to unscramble the letters in Column one and match them with their properties in Column two. The scrambled words are: T R E M A T, U L S B E L O, T N E R P A S N A R T, and E R U S T L. The properties to match are: Objects can be seen clearly through it, Occupies space and has mass, Shiny surface, and Mixes completely in water. Unscramble them and draw the correct connections.
Exercise three asks: The containers which are used to store materials in shops and at home are usually transparent. Give your reasons for this.
Exercise four asks you to state whether the statements given below are True or False, and correct the false statements. First: Wood is translucent while glass is opaque. Second: Aluminium foil has lustre while an eraser does not. Third: Sugar dissolves in water whereas sawdust does not. Fourth: An apple is a matter because it occupies no space and has mass.
Exercise five presents chairs made up of various materials, such as wood, iron, plastic, bamboo, cement and stones. It lists desirable properties: hardness, lightweight, does not feel very cold in winter, and can be cleaned regularly. Which materials used to make chairs fulfil these properties the most?
Exercise six asks you to choose materials for containers to collect food waste, broken glass, and wastepaper. Which materials will you choose for containers of these types of waste? What properties of materials do you need to think of?
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Exercise seven states: Air is all around us but does not hinder us from seeing each other. Whereas, if a wooden door comes in between, we cannot see each other. It is because air is blank and the wooden door is blank. Choose the most appropriate option from the given pairs.
Exercise eight presents a scenario with two mysterious materials, X and Y. When you try to press material X, it feels rigid and does not change its shape easily. On the other hand, material Y easily changes its shape when you press it. Now, when you mix both materials in water, only material X dissolves completely, while material Y remains unchanged. What can materials X and Y be? Can you identify whether material X is hard or soft? What about material Y? Justify your answer.
Exercise nine asks: Who am I? Identify me on the basis of the given properties. Part a: I have lustre. Part b: I can be easily compressed. Part c: I am hard and soluble in water. Part d: You cannot see clearly through me. Part e: I have mass and volume but you cannot see me. Part ii asks you to make your own Who am I riddle.
Exercise ten provides the following materials: vinegar, honey, mustard oil, water, glucose and wheat flour. Make any two pairs of materials where one material is soluble in the other. Now, make two pairs of materials where one material remains insoluble in the other material.
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In the Learning further section, you are asked to gather information on different materials which can be recycled. You can take help from various sources, such as newspapers, magazines, elders in your community, and the internet. Recyclers buy old objects based on properties of the materials and do not bother even if an object is broken. Conduct a survey with recyclers near you and find out what properties of materials do they check before buying objects from households. Which materials do they not buy and why? Collect twenty to thirty objects from your household and classify them based on the properties of the materials they are made up of. Were you able to put them in separate groups? What relationship do you see between the properties of the materials and the use of the objects? Create and decorate a useful object of your choice using discarded materials and bring it to the class. Discuss with your friends what they have made and the materials they have used. Additionally, provide constructive feedback on areas for improvement, considering functionality and any other points.
Thank you for listening! Keep revising and practicing. Goodbye! [CHAPTER_COMPLETE]