उपादानं भवेत्तस्याा (मूषाया:) मृत्तिका लोहमेव च ।(रसरत्ननसमुच्चय–१०.३)
The materials used to make the crucible (a vessel used to melt substances) are clay and iron.
(Rasaratnasamuchchaya–10.3)
6.1 Observing Objects Around Us
Ghulan and Sheeta are thrilled to go to their new class after the summer break. They enter their classroom and start talking. “What have you brought to school today?” asks Sheeta.
I also have a new notebook and a pen.
Look, I have a new notebook.
After some time, Madam Vidya, their science teacher, enters the class and starts interacting with the students to draw their attention to many things they use in their daily life. She asks, “How are they similar to or different from each other? What are their shapes and colours? How does it feel when you touch them? Are some of them heavier than
others?” All things are made up of some materials like paper, wood, cloth, glass, metal, plastic, clay, and so on.Any substance that is used to create an object is referred to as material.
Activity 6.1: Let us identify
Make a list of objects you see around and also write the names of the materials they are made up of in Table 6.1.
I observeMaterials they are made up of
Based on everyday observations, one can conclude that objects are made up of various materials.
The earliest pottery found in the Indian subcontinent dates back to 7,000 to 8,000 years in the Ganga plains (Lahuradewa) and in Baluchistan (Mehrgarh). About 4000 BCE onwards, Sindhu-Sarasvatī developed techniques of wheel-turned pottery production, pigmentation, application of protective or decorative coats (called ‘slips’) of multiple colours, decorative painting, etc. These techniques became further sophisticated during the Sindhu-Sarasvatī (also known as ‘Harappan’) Civilisation (2600–1900 BCE), 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, New Delhi.
Do you know?
Let us explore materials further.
6.2 How to Group Materials?
Activity 6.2: Let us group
• Group the objects shown in Fig. 6.1 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 to group the objects in Activity 6.2?
• Did your friends group objects based on similar properties?
• What did you learn from this activity?
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.
Activity 6.3: Let us think
Let us think what materials we can use to make a tumbler. Fill in the names of the materials in the spaces provided in Fig. 6.2.
Tumbler
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.
Can a cricket ball be used to play tennis?
Why are different materials used for making balls for various sports?
Activity 6.4: Let us explore
Fig. 6.3 illustrates a variety of balls that are of the same size but made up of different materials.
• Take each ball and drop it from a fixed height.
• Note the height to which the ball bounces and record it in Table 6.2.
• Identify the ball that achieves the highest bounce.
Tennis ballCricket ballHand exercise ball
BallBounce (high, medium or low)
Tennis ball
Cricket ball
Hand exercise ball
Any other
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.Observe Fig. 6.4 and group the objects in as many different ways as possible.
You might have grouped these objects according to their shapes or by their colour or materials they are made up of.We have learnt that materials may be classified on the basis of their properties. For example, in the kitchen, we usually store things in such a manner where similar utensils are placed together. Similarly, a grocer usually keeps all types of spices in one corner, pulses and grains in another corner and so on. You may also visit any chemist shop and enquire about how medicines are arranged.
6.3 What are the different Properties of Materials?
Let us learn some more properties of materials.
6.3.1 Observe and identify appearance of materials
Materials often look different from each other. Freshly cut wood, which is unpolished, has a distinct appearance, quite different from that of iron. Similarly, iron looks different from copper or aluminium. However, there might be some similarities among iron, copper and aluminium 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, etc. Take a look at the pieces you have collected. Do any of these materials shine when light falls on them? Observe their texture (whether
rough or smooth), colour and other noticeable features, and record your observations in the notebook. Group the collected pieces based on their 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, etc. 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, etc.“All that glitters is not gold” goes an old saying! Not all the 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.
Are all lustrous materials metals?
6.3.2 Which materials are hard?
When you press different objects or materials with your hands, some of them 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.
Activity 6.5: Let us observe
• Hold the objects given in Table 6.3 with your hands.Feel whether the objects are hard or soft. Find out the materials they are made up of. Enter your observations in Table 6.3.
ObjectHard/SoftMaterial(s)
BrickHardBaked clay
Water bottle
Pillow
Tumbler
Table
Sweater
Any other
• Compare your observations with the observations of your friends and discuss.
You have learnt that materials can have different properties, like lustre, hardness, softness and colour. Can you think of any other properties that are shown by materials? Let us explore it further.
6.3.3 Explore materials through which one can see or cannot see
Ghulan, Sheeta and Sara are playing hide and seek with their friends. Ghulan hides behind a wall, Sheeta hides behind a big tree in the garden while Sara hides behind the 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, etc., are some examples of transparent materials.Why did Ghulan, Sheeta and Sara choose these places to hide?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 Fig. 6.5. Identify and label the nature of materials used by Ghulan (A), Sheeta (B), Sara (C) and Sheeta’s brother (D).
(A) (B) (C) (D) .
Activity 6.6: Let us classify
Classify the following objects as transparent, translucent or opaque in Table 6.4.
Glass tumbler
Butter paper
Eraser
Wooden board
Frosted glass
Window glass
Is water transparent? Can it be made opaque? ?
TransparentTranslucentOpaque
6.3.4 What is soluble in water; what is not?
Ghulan was sweating when he came home after playing in the evening. He was feeling tired and thirsty. Ghulan’s mother mixed a spoonful of sugar, a pinch of salt and some lemon juice in a glass tumbler of water and offered him this shikanji (lemonade) to drink.Ghulan noticed that while his mother was mixing sugar and salt in water, the salt and the sugar disappeared after a while. Let us try a simple activity to explore how different materials behave when we mix them in water!
Activity 6.7: 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 6.5.
PredictionObservation
Will disappear in water/will not disappear in water
Disappears in water/does not disappear in water
Material
Sugar
Salt
Chalk powder
Sand
Sawdust
Any other
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 (Fig. 6.6a). 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 (Fig. 6.6b). Water plays an important role in the functioning of our body because it can dissolve a large number of materials.
Does everything you put in water disappear? ?
(a) Soluble material in water
(b) Insoluble material in water
Make your own ORS!
ORS—Oral Rehydration Solution— is used to treat dehydration due to diarrhoea or other illnesses. These ready-made ORS packets are available in primary health centres and also 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.
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.
6.3.5 How heavy or light?
Activity 6.8: Let us measure
• Let us 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 (Fig. 6.7) and record the readings in your notebook.
• Compare the data and infer which is heavier or lighter.
From Activity 6.8, 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.
6.3.6 Space and volume
Next day, Madam Vidya enters the class. All the students stand up to greet her. She reciprocates and deliberately says, “Please keep your bags on your seats and sit down.” Students are not able to sit because bags are kept on their seats. Madam Vidya asks, “Why are you not sitting?” The students reply that there is no place to sit because the bags have occupied that space.Continuing the conversation, she provides two identical glass tumblers to two students and encourages them to pour the remaining water from their drinking water bottles into the respective glass tumblers. On pouring water in the glass tumblers, the students observe that one glass tumbler gets half-filled with water (Fig. 6.8a) while the other is almost completely filled with water (Fig. 6.8b).
(a) Half-filled(b) Fully-filled
Why is the level of water different in the two tumblers?Madam Vidya elaborates that both tumblers have the same capacity. The water levels differ in each case, which indicates that the amount of water in each tumbler is different. 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.
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 being sold in the market. Have you noticed 1 L, 500 mL, 200 mL, etc., written as net quantity on the bottles? These indicate the volume of water in the bottles.
The bottles of drinking water and milk are labelled as 500 mL, indicating the volume.
Drinking water500 mL
Milk500 mL
Now you have become familiar with many properties of materials. However, all materials do not possess all these properties.
Are there any properties which can be shown by all materials? If yes, what are those?
6.4 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 (g) and kilogram (kg). The space occupied by matter is its volume. The units to measure the volume are litre (L) and millilitre (mL).
Kilogram is the unit of mass in the International System of Units (SI). 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 (numerical value) and the unit. For example, if we have mass of 7 kilograms, 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 millilitres of water, it would be written as 500 mL, m will be in lower case and L will be in upper case. The SI unit for volume is cubic metre, abbreviated as m3. 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 m3. Always leave a space between number (numerical value) and the unit. 1 m3 =1000 L.
Do you know?
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 learnt that materials look different and behave differently. We grouped materials on the basis of similarities or differences in their properties. We find grouping useful as it helps us study and observe patterns in the properties of things. Humans have been classifying not only things, but also rocks, plants and animals. We have learnt about the classification of the living world in the chapter ‘Diversity in the Living World’. Just like in the living world, classification of the non-living world is also done on the basis of their properties.
Is air matter?
Can you think about what changes the invention of plastic brought to humans? Is it a boon or a bane? Think it over!
Yes! But most of the materials that we see today would have also existed earlier. I am curious to know how people classified them then.
We have explored and understood the various properties of materials.
A similar classification system existed in ancient India. Ayurveda, one of the Indian medical systems, too has a system of grouping things.गुŁ मन्द हिम स्निग्ध श्लक्ष्ण सान्द्र मृददु स्थिराः|गुणणाः ससूक्ष्मम विशददा: विंशतिः स विपर्ययाः||
(Aṣhtanga hṛidaya Sūtra sthāna 1.18)The shloka precisely talks about the 20 properties (guṇa—ten pairs of opposite properties), which are used to describe all physical matter in Ayurveda. These properties can also be used to describe all living systems (plants, animals and humans), the environment and also food.These properties are:(i) guru (heavy) laghu (light in weight)(ii) manda (slow) tīkṣhṇa (quick, fast) (iii) hima (cold) uṣhṇa (hot)(iv) snigdha (unctous) rukṣha (dry)(v) śhlakṣhaṇa (smooth) khara (rough)(vi) sāndra (solid) drava (liquid)(vii) mṛidu (soft) kaṭhina (hard)(viii) sthira (stable) khāla (moving, unstable)(ix) sūkṣhma (subtle, small) sthūla (big, gross)(x) viśhada (non slimy) picchhila (slimy)Do you know?
Keywords
Non-lustrous
Classify
Classification
Opaque
Explore
Hard
Soft
Identify
Insoluble
Soluble
Observe
Lustrous
Translucent
Predict
Mass
Transparent
Record
Material
Volume
Matter
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.
Let us play
1. Find the companion.
Link the following words by putting arrows between words that have a connection.
Iron
TransparentCopper
SolidBottle
PlasticLustrous
WoodOpaque
Glass
2. Win the ‘Word-hub’
The following words from the chapter like lustrous, non-lustrous, soluble, insoluble, hard, soft, matter, mass, transparent, opaque, volume and translucent are picked up.
Grid
• Students should randomly choose nine words from the given list and write them in the 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/her words are marked correctly.