Textbook-based subjective questions

( :) ( – .) The materials used to make the crucible (a vessel used to melt substances) are clay and iron. (Rasaratnasamuchchaya–10.3)

They enter their classroom and start talking.

Look, I I also have a have a new new notebook notebook. and a pen. 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.

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. 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).

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

These techniques became further sophisticated during the Sindhu-Sarasvatī (also known as ‘Harappan’) Civilisation

Pots were used for various purposes, from cooking to storage of food grains, oil, ghee, and so on.

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 Materials Around Us

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. use paper-like cloth be used for materials for storing water? making cooking utensils?

use paper-like cloth be used for materials for storing water? making cooking utensils?

What decides which material should be used for making an object?

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.

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. 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.

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.

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 Fig. 6.4: Grouping of objects where similar utensils are placed together.

6.4: Grouping of objects where similar utensils are placed together.

6.3 What are the different Properties of Materials?

6.3.1 O bserve and identify appearance of materials Materials often look different from each other. 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.

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?

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.

Materials that typically have shiny surfaces are said to have a lustrous appearance.

Examples of metals include iron, copper, zinc, aluminium, gold, etc.

As a result, we often notice the lustre only on their freshly cut surfaces. Non-lustrous Are all lustrous materials are those that do not have a shiny materials metals? surface.

“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. 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.

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.

Materials which can be compressed or scratched easily are soft, while other materials which are difficult to compress or scratch are hard.

Activity 6.5: Let us observe Hold the objects given in Table 6.3 with your hands.

Find out the materials they are made up of. 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?

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).

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.

Do you think it would be possible for Sheeta’s brother to see her and her friends through a closed wooden window of 108 the house?

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. Identify and label the nature of materials used by Ghulan (A), Sheeta (B), Sara (C) and Sheeta’s brother (D).

6.3.4 What is soluble in water; what is not? Ghulan was sweating when he came home after playing in the evening. 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’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!

Let us try a simple activity to explore how different materials behave when we mix them in water!

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.

We say that these materials dissolve in everything you water or, in other words, they are soluble put in water in water (Fig. Some materials do not disappear? mix with water and do not disappear even after we stir them for a long time.

These materials are insoluble in water (Fig. Water plays an important role in the functioning of our body because it can dissolve a large number of materials.

(a) Soluble material in water (b) Insoluble material in water Fig. 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.

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.

l, Do liquids like oi What about the gases ney vinegar and ho present in water? er? dissolve in wat Explore.

Some do not mix with water and form a separate layer when left undisturbed for some time.

For example, oxygen gas dissolves in water. It is very important for the survival of animals and plants that live in water.

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?

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.

The one which is heavier has more mass and the one which is lighter has less mass. 6.7: Weighing a paper cup containing water Weight is sometimes used in common language for mass as it is determined by weighing.

Weight is sometimes used in common language for mass as it is determined by weighing.

6.3.6 Space and volume Next day, Madam Vidya enters the class.

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 Materials Around Us tumblers, the students observe that one glass tumbler gets half- filled with water (Fig.

6.8a) while the other is almost completely (a) Half-filled (b) Fully-filled filled with water (Fig. 6.8: Glass tumblers with varying levels of water Why is the level of water different in the two tumblers?

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.

Why was I not able to transfer water from the jug into an empty water bottle completely?

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.

Now you have become familiar with many properties of materials. However, all materials do not possess all these properties.

If ye s, Mass and volume are the two what are those ? 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.

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 space occupied by matter is its volume.

Kilogram is the unit of mass in the International System of Units (SI).

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.

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 Materials Around Us

The abbreviation is written with a superscript 3 to Materials Around Us For example, if you have volume of 2 cubic metres, it would be written Do you as 2 m3. Always leave a space between number know?

Always leave a space between number know?

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. 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. Can you think about what changes the invention of plastic brought to humans? Think it Is it a boon or a bane? over!

But most of the materials that we see today would have We have explored also existed earlier. I am and understood the curious to know how people A similar classification system existed in ancient India.

A similar classification system existed in ancient India.

These properties can also be used to describe all living systems (plants, animals and humans), the environment and also food.

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.

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. 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.

Visit your kitchen and observe how your parents have organised various edibles. Can you suggest a better sorting method? Unscramble the letters (Column I) and match with their properties (Column II).

Unscramble the letters (Column I) and match with their properties (Column II). clearly through it (ii) U L S B E L O (b) Occupies space and has mass (iii) T N E R P A S N A R T (c) Shiny surface (iv) E R U S T L (d) Mixes completely in water The containers which are used to store materials in shops and at home are usually transparent.

The containers which are used to store materials in shops and at home are usually transparent.

We see chairs made up of various materials, such as wood, iron, plastic, bamboo, cement and stones.

Which materials used to make chairs fulfil these properties the most? (i) Hardness (does not bend or shake on sitting even after long use).

(ii) Lightweight (easy to lift or to take from one place to another). (iii) Does not feel very cold when sitting during winters.

(iv) Can be cleaned regularly and made to look new even after long use. You need to have containers for collection of: (i) food waste, (ii) broken glass and (iii) wastepaper. Which materials will you choose for containers of these types of waste?

What properties of materials do you need to think of? Air is all around us but does not hinder us from seeing each other. Whereas, if a wooden door comes in between, we

Whereas, if a wooden door comes in between, we

Choose the most appropriate option: (i) transparent, opaque (ii) translucent, transparent (iii) opaque, translucent (iv) transparent, translucent 8.

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.

Can you identify whether material X is hard or soft? Identify me on the basis of the given properties.

(a) I have lustre. (b) I can be easily compressed. (c) I am hard and soluble in water. (d) You cannot see clearly through me. (e) I have mass and volume but you cannot see me. (ii) Make your own ‘Who am I?’ 10. You are provided with 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.

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. Gather information on different materials which can be recycled.

Gather information on different materials which can be recycled.

Which materials do they not buy and why? Collect 20–30 objects from your household and classify them based on the properties of the materials they are made up of.

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.

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.