CBSE Class 6- Science Chapter 6: Materials Around Us – Study Notes (PDF)

Study Notes: Materials Around Us (Class 6-NCERT(Curiosity) Science

1. Introduction to Materials and Objects

• Material: Any substance used to create an object. Examples include paper, wood, cloth, glass, metal, plastic, and clay.
• Object: A thing made from one or more materials. Objects around us vary in shape, colour, and texture.
• Key Principles:
  • An object can be made from a single material or a combination of different materials (e.g., a pen made of plastic, metal, and ink).
  • A single material can be used to make many different objects (e.g., wood can be used to make chairs, tables, and doors).
  • The choice of material for an object depends on the material’s properties and the object’s intended purpose. For example, a tumbler must be made of a material that can hold water, making materials like cloth or paper unsuitable.

2. Grouping and Classification of Materials

• Classification: The method of arranging objects or materials into groups based on common properties, similarities, or differences.
• Purpose of Classification: Grouping materials and objects helps in studying them systematically and observing patterns in their properties. This is a common practice in various settings, such as kitchens, grocery stores, and chemist shops, to organize items efficiently.
• Bases for Classification: Objects and materials can be grouped based on various properties, including:
  • Shape
  • Color
  • Hardness or softness
  • Lustre (shine) or dullness
  • The material they are made of

3. Key Properties of Materials

3.1 Appearance

• Lustrous: Materials that have a shiny surface, often referred to as lustre. Metals like iron, copper, gold, and aluminum are typically lustrous. Some metals may lose their lustre due to exposure to air and moisture, but the shine is visible on freshly cut surfaces.
• Non-Lustrous: Materials that do not have a shiny surface. Examples include paper, wood, rubber, and jute.
• Important Note: Not all shiny materials are metals. Some surfaces are made shiny by polishing or coating them with other materials like plastic or wax.

3.2 Hardness

• Hard Materials: Materials that are difficult to compress or scratch. Examples include stone, iron, and wood.
• Soft Materials: Materials that can be easily compressed or scratched. Examples include erasers, candles, and chalk.
• Relativity of Hardness: Hardness is a relative property. For instance, rubber is harder than a sponge but softer than iron.

3.3 Transparency

• Transparent: Materials through which objects can be seen clearly. Light passes through them completely. Examples include glass, water, air, and cellophane paper.
• Opaque: Materials through which objects cannot be seen at all. They block light completely. Examples include wood, cardboard, and metals.
• Translucent: Materials through which objects can be seen, but not clearly. They allow some light to pass through in a scattered manner. Examples include butter paper and frosted glass.

3.4 Solubility in Water

• Soluble: Materials that completely dissolve or disappear when mixed in water. Examples include sugar, salt, and oxygen gas. Water’s ability to dissolve many substances is crucial for bodily functions.
• Insoluble: Materials that do not mix with water and do not disappear, even after stirring. Examples include sand, chalk powder, sawdust, and oil. Some liquids form a separate layer, and some solids settle at the bottom.

3.5 Mass (Heaviness/Lightness)

• Mass: A property that quantifies the amount of matter in an object. Objects that are heavier have more mass, while lighter objects have less mass.
• Measurement: Mass is measured using a balance. In common language, “weight” is often used interchangeably with mass. The standard units are the gram (g) and kilogram (kg).

3.6 Volume (Space Occupied)

• Volume: The amount of space occupied by an object or substance.
• Concept: Every object occupies space. For example, a bag on a seat occupies the space, preventing someone from sitting there. The amount of water in a container represents its volume.
• Measurement: The units used to measure volume include litre (L), millilitre (mL), and the SI unit, cubic metre (m³).

4. The Concept of Matter

• Definition: Anything that occupies space (has volume) and has mass is called matter.
• Universal Properties: Mass and volume are the two fundamental properties possessed by all materials.
• Examples: All materials we encounter, including solids (sand, pebbles), liquids (water), and gases (air), are forms of matter.

5. Historical and Cultural Context

• Ancient Pottery: The earliest pottery in the Indian subcontinent dates back 7,000 to 8,000 years. The Sindhu-Sarasvatī (Harappan) Civilization (2600–1900 BCE) developed sophisticated techniques for making terracotta (baked clay) pottery, which was used for cooking and storage.
• Ayurveda Classification: The ancient Indian medical system of Ayurveda uses a system of 20 properties (guṇa), arranged in ten opposite pairs, to describe all physical matter, living systems, and food. These pairs include heavy/light, cold/hot, soft/hard, and smooth/rough.

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Quiz

Short-Answer Questions

(Answer in 2-3 sentences)

1. What is the definition of a “material”? Provide two examples.
2. Explain the concept of “classification” as it relates to objects and materials.
3. Why is a tumbler for drinking water not made of cloth?
4. Describe the property of “lustre.” Name one lustrous and one non-lustrous material.
5. What can cause a lustrous metal to appear dull over time?
6. How can one distinguish between a hard material and a soft material? Give an example of each.
7. Define a “transparent” material and provide two examples.
8. What are “opaque” materials? Why did Ghulan hide behind a wall in the hide-and-seek game?
9. Explain what makes a material “translucent.” Give an example from the text.
10. What does it mean for a substance to be “soluble” in water?
11. Give an example of two materials from the text that are insoluble in water.
12. Why is the solubility of oxygen gas in water important?
13. What is “matter”? What are its two fundamental properties?
14. How are “mass” and “volume” defined in the context of materials?
15. What are the standard units used to measure mass and volume?
16. Briefly describe the sophistication of pottery during the Sindhu-Sarasvatī Civilization.
17. What is terracotta?
18. According to the text, how can one prepare a homemade Oral Rehydration Solution (ORS)?
19. Explain why different sports use balls made from different materials.
20. What is the difference between an object and a material?
21. Why is grouping materials considered useful?
22. Is hardness an absolute or a relative property? Explain with an example.
23. In the hide-and-seek scenario, Sheeta’s brother could see everything. What does this imply about the window he was looking through?
24. What happens when a liquid that is insoluble in water is mixed with it?
25. According to Ayurveda, how many primary properties (guṇa) are used to describe physical matter?

Multiple-Choice Questions (MCQs)

1. Which of the following is the best definition of a material? A) Any object found in nature. B) Any substance used to create an object. C) Only hard and shiny substances. D) Only substances that dissolve in water.
2. The method of arranging objects into groups based on common properties is called: A) Combination B) Separation C) Classification D) Observation
3. Which property determines that a metal like iron is a “lustrous” material? A) It is hard. B) It is opaque. C) It has a shiny surface. D) It is heavy.
4. Materials that are difficult to compress or scratch are known as: A) Soft B) Hard C) Translucent D) Soluble
5. A material through which you can see objects clearly is called: A) Opaque B) Translucent C) Transparent D) Non-lustrous
6. Frosted glass and butter paper are examples of which type of material? A) Opaque B) Translucent C) Transparent D) Lustrous
7. Which of the following substances is described as soluble in water? A) Sand B) Sawdust C) Sugar D) Chalk powder
8. Anything that occupies space and has mass is defined as: A) Volume B) Matter C) An object D) A property
9. The space occupied by matter is its: A) Mass B) Lustre C) Hardness D) Volume
10. Which units are used to measure mass? A) Litre and millilitre B) Metre and centimetre C) Gram and kilogram D) Lustre and hardness
11. According to the text, the earliest pottery in the Indian subcontinent dates back to: A) 1000–2000 years ago B) 2600–1900 BCE C) 4000 BCE D) 7,000 to 8,000 years ago
12. Baked clay is also known as: A) Crucible B) Terracotta C) Sindhu-Sarasvatī D) Pigmentation
13. Which of the following is an example of an opaque material? A) Water B) Air C) A wooden board D) A glass tumbler
14. The property that makes a material suitable for making cooking utensils is NOT: A) Hardness B) Being a metal C) Being made of paper D) Opaqueness
15. Why is oxygen dissolved in water important? A) It makes the water transparent. B) It is crucial for the survival of aquatic animals and plants. C) It helps other materials dissolve. D) It prevents water from becoming opaque.
16. What is the SI unit for volume? A) Litre (L) B) Millilitre (mL) C) Kilogram (kg) D) Cubic metre (m³)
17. Which of these is a pair of opposite properties described in the ancient Indian system of Ayurveda? A) Hard and Lustrous B) Heavy and Light C) Transparent and Opaque D) Soluble and Dry
18. What does ORS stand for? A) Oxygen Replacement System B) Opaque Rehydration Salt C) Oral Rehydration Solution D) Object Reordering System
19. Which of the following materials is non-lustrous? A) Gold B) Copper C) Freshly cut iron D) Wood
20. A single object, like a pen, can be made from: A) Only one material B) A combination of different materials C) Only transparent materials D) Only soft materials

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Answer Keys

Short-Answer Questions Answer Key

1. A “material” is any substance used to create an object. Examples from the text include paper, wood, cloth, glass, metal, and plastic.
2. “Classification” is the process of organizing or arranging objects and materials into groups. This grouping is based on shared characteristics, such as shape, colour, hardness, or the materials they are made of.
3. A tumbler made of cloth cannot be used for drinking water because cloth is not capable of holding water. Its properties are unsuitable for this purpose, as the water would leak through it.
4. “Lustre” is the property of having a shiny surface. A material like copper is lustrous, whereas a material like wood is non-lustrous.
5. A lustrous metal can appear dull due to the effect of air and moisture on its surface over time. This reaction causes it to lose its shine.
6. A hard material is difficult to compress or scratch, like a stone. A soft material can be easily compressed or scratched, like an eraser.
7. A “transparent” material is one through which things can be seen clearly. Examples include glass, water, and air.
8. “Opaque” materials are those through which you cannot see at all. Ghulan hid behind a wall because it is opaque, which prevented others from seeing him.
9. A “translucent” material allows objects to be seen, but not clearly, because it scatters light. An example given in the text is frosted glass or butter paper.
10. A substance is “soluble” if it dissolves completely when mixed in water, seeming to disappear. Sugar and salt are common examples of soluble materials.
11. The text provides several examples of materials insoluble in water, including sand and sawdust. These materials do not mix with water and remain visible after stirring.
12. The solubility of oxygen gas in water is very important for the survival of animals and plants that live in water. They use this dissolved oxygen to breathe.
13. “Matter” is defined as anything that occupies space and has mass. These two properties, volume (occupying space) and mass, are its fundamental characteristics.
14. “Mass” is the property that quantifies the amount of matter in an object, determining how heavy it is. “Volume” is the amount of space that matter occupies.
15. The standard units for measuring mass are the gram (g) and kilogram (kg). The units for measuring volume are the litre (L), millilitre (mL), and cubic metre (m³).
16. The Sindhu-Sarasvatī Civilization developed advanced pottery techniques, including wheel-turned production, pigmentation, and the application of decorative coats. Their pottery featured a bright red surface with black-colored geometric and animal designs.
17. Terracotta is clay that has been baked in a kiln. This process makes the clay hard and durable.
18. A homemade ORS can be prepared by mixing six teaspoons of sugar and half a teaspoon of common salt in one litre of boiled and cooled water.
19. Different sports balls are made from different materials because each sport requires specific properties. These properties include how high the ball bounces, its size, texture, and hardness, which are all determined by the material used.
20. A material is the substance (e.g., wood, plastic) from which things are made. An object (e.g., a chair, a bottle) is the final product created from one or more materials.
21. Grouping materials is useful because it helps us to study their properties systematically and observe patterns. This organization makes it easier to understand and utilize them effectively.
22. Hardness is a relative property because a material can be harder than one substance but softer than another. For example, rubber is harder than a sponge but softer than iron.
23. If Sheeta’s brother could see everything clearly, it implies he was looking through a transparent material. The text specifies he was looking through a glass window of his house.
24. When a liquid that is insoluble in water is mixed with it and left undisturbed, it forms a separate layer. It does not mix completely with the water.
25. According to Ayurveda, there are 20 primary properties (guṇa), organized into ten pairs of opposites, which are used to describe all physical matter.

Multiple-Choice Questions Answer Key

1. B) Any substance used to create an object.
2. C) Classification
3. C) It has a shiny surface.
4. B) Hard
5. C) Transparent
6. B) Translucent
7. C) Sugar
8. B) Matter
9. D) Volume
10. C) Gram and kilogram
11. D) 7,000 to 8,000 years ago
12. B) Terracotta
13. C) A wooden board
14. C) Being made of paper
15. B) It is crucial for the survival of aquatic animals and plants.
16. D) Cubic metre (m³)
17. B) Heavy and Light
18. C) Oral Rehydration Solution
19. D) Wood
20. B) A combination of different materials

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Essay Questions and Answers

1. Explain the relationship between the properties of a material and its use in making a specific object. Use the examples of a cooking utensil and a sports ball to support your answer.

Answer: The choice of a material for making an object is fundamentally determined by the material’s properties and the intended purpose of the object. An object’s function dictates the properties its material must possess. For example, a cooking utensil needs to be made from a material that is hard, durable, and can withstand heat, which is why metals are commonly used; using a material like paper would be inappropriate as it would burn. Similarly, a sports ball’s function depends on its material properties. A tennis ball is made to be lightweight and bouncy, while a cricket ball is made to be hard and less bouncy. Using a cricket ball for tennis would not work because its properties (heavy, hard) are unsuitable for the game’s requirements. This demonstrates that there is a direct and crucial link between a material’s inherent characteristics and its functional application in an object.

2. Describe the three categories of materials based on their interaction with light: transparent, translucent, and opaque. Provide examples for each and explain how these properties are relevant in everyday life, using the hide-and-seek game from the text as a central example.

Answer: Materials are categorized into three groups based on how they interact with light. Transparent materials, like glass and water, allow light to pass through completely, so objects can be seen clearly through them. Translucent materials, such as frosted glass or butter paper, allow some light to pass but scatter it, so objects are visible but not clearly. Opaque materials, like wood and metal, block all light from passing through, making it impossible to see through them. These properties are highly relevant in daily life. In the hide-and-seek game, the children intuitively use these properties. Ghulan hides behind an opaque wall, ensuring he cannot be seen at all. Sara hides behind a translucent frosted glass door, making her difficult but not impossible to see. Sheeta’s brother, however, can see everyone clearly through his transparent glass window, which offers an unobstructed view.

3. Define “matter” and its two essential properties. Explain how the concepts of mass and volume are demonstrated in the classroom activities described in the text.

Answer: Matter is defined as anything that occupies space and has mass. These two characteristics—volume (the space it occupies) and mass (the quantity of matter)—are the essential properties of all matter. The classroom activities illustrate these concepts clearly. The concept of volume is shown when students cannot sit on their seats because their bags are occupying the space. It is further demonstrated when water from bottles is poured into identical tumblers; the different water levels show that the water occupies different amounts of space (volume). The concept of mass is explored by filling three identical cups with water, sand, and pebbles. By weighing each cup, one can observe that even though they occupy a similar volume, they have different weights, meaning they have different amounts of mass; the one that is heavier has more mass.

4. Compare and contrast soluble and insoluble materials. Using the examples from Activity 6.7 (sugar, salt, chalk powder, sand, sawdust), describe the process and observations for determining solubility in water.

Answer: Soluble and insoluble describe a material’s ability to dissolve in a liquid, specifically water in this context. Soluble materials are those that completely disappear or mix into water when stirred, like sugar and salt. Insoluble materials do not mix with water and remain as separate substances, even after extensive stirring, like sand and sawdust. In Activity 6.7, this difference is observed by taking five tumblers of water and adding one material to each. When sugar and salt are stirred into the water, they dissolve and the water remains clear, demonstrating they are soluble. However, when chalk powder, sand, and sawdust are stirred, they do not disappear. The sand and chalk powder settle at the bottom, and the sawdust may float, showing they are insoluble in water. This simple experiment effectively distinguishes between the two types of materials based on their interaction with water.

5. What is “classification” and why is it a useful practice? Provide examples of how materials can be grouped based on at least four different properties mentioned in the chapter.

Answer: Classification is the systematic method of arranging objects or materials into groups based on their similarities or differences. This practice is useful because it helps us to study and observe patterns in their properties, making the world around us more organized and easier to understand. Materials can be classified based on several properties mentioned in the chapter:

1. Appearance: Grouping based on whether they are lustrous (e.g., copper, aluminum) or non-lustrous (e.g., paper, wood).
2. Hardness: Separating materials into hard (e.g., stone, iron) and soft (e.g., eraser, sponge) categories based on their resistance to compression.
3. Transparency: Classifying them as transparent (glass), translucent (butter paper), or opaque (cardboard) depending on how much light passes through them.
4. Solubility: Dividing them into soluble (e.g., salt) and insoluble (e.g., sand) based on their ability to dissolve in water.

6. Discuss the historical significance of materials as described in the text, focusing on the development of pottery in the Indian subcontinent.

Answer: The text highlights the long history of human interaction with materials through the example of pottery. The earliest evidence of pottery in the Indian subcontinent dates back 7,000 to 8,000 years, indicating an early understanding of how to manipulate natural materials like clay. This skill became highly sophisticated during the Sindhu-Sarasvatī (Harappan) Civilization (2600–1900 BCE). During this period, techniques included wheel-turned pottery, pigmentation, applying protective and decorative coats called ‘slips’, and painting with complex geometric and animal designs. The clay was carefully selected, cleaned, and finally baked in kilns to create terracotta, which was used for vital purposes like cooking and storing food grains and liquids. This historical context shows that understanding and utilizing material properties is not a modern concept but a foundational aspect of human civilization.

7. Is “hardness” an absolute property? Explain your reasoning using an example provided in the source context.

Answer: No, “hardness” is not an absolute property; it is relative. The text explains this by comparing how a material’s hardness can change depending on what it is being compared to. A material can be considered hard in one context and soft in another. The example given is rubber, which is harder than a sponge because it is more difficult to compress. However, the same piece of rubber is softer than iron because it can be compressed more easily than iron. This demonstrates that hardness is a comparative property, not a fixed, absolute value.

8. Explain the importance of water’s property as a solvent for living organisms, as mentioned in the text.

Answer: The text states that “Water plays an important role in the functioning of our body because it can dissolve a large number of materials.” This property makes water an excellent solvent. Furthermore, it mentions that oxygen gas dissolves in water, which is “very important for the survival of animals and plants that live in water.” These points together highlight that water’s ability to dissolve substances is critical for life. Within our bodies, it transports nutrients and other essential substances, and in aquatic environments, it holds the dissolved oxygen necessary for respiration.

9. The text mentions an ancient Indian system of classification from Ayurveda. Describe this system and compare its approach to the modern scientific properties discussed in the chapter.

Answer: The ancient Indian medical system of Ayurveda uses a classification system based on 20 properties (guṇa), which are organized into ten pairs of opposites. These properties are used to describe all physical matter, including living systems and food. The pairs include concepts like guru (heavy) vs. laghu (light), mṛidu (soft) vs. kaṭhina (hard), and śhlakṣhaṇa (smooth) vs. khara (rough). This Ayurvedic approach is conceptually similar to the modern scientific properties discussed in the chapter, as both systems use observable physical characteristics to group and understand materials. Properties like heavy/light correspond to mass/density, soft/hard corresponds to hardness, and smooth/rough corresponds to texture. While the scientific method focuses on quantifiable measurements, the Ayurvedic system provides a qualitative framework for understanding the nature of materials.

10. What is the distinction between mass and volume? Using the experiment with the school bags and the water in tumblers, illustrate how an object can have volume but different objects can have different masses for the same volume.

Answer: Mass and volume are two distinct and fundamental properties of matter. Volume is the amount of space an object occupies, while mass is the quantity of matter it contains. An object must have both, but they are not the same. The school bag example shows volume: the bag takes up space on the seat, preventing a person from occupying that same space. The activity with filling identical cups with water, sand, and pebbles illustrates the difference between mass and volume. The materials fill the same amount of space in the cups (similar volume), but when weighed, they show different readings. The cup of pebbles is heavier (has more mass) than the cup of sand, which in turn is heavier than the cup of water. This proves that different materials can have different masses even when they occupy the same volume.

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Glossary of Key Terms

Term	Definition
Classification	The method of arranging objects or materials into groups based on common properties, similarities, or differences.
Hard	A property of materials that are difficult to compress or scratch.
Insoluble	A property of materials that do not mix with or dissolve in water.
Lustrous	A property of materials that have a shiny surface or appearance.
Mass	A fundamental property of matter that quantifies the amount of matter present in an object. It is measured in grams (g) and kilograms (kg).
Material	Any substance that is used to create an object (e.g., wood, glass, plastic).
Matter	Anything that occupies space (has volume) and has mass.
Non-Lustrous	A property of materials that do not have a shiny surface; they appear dull.
Opaque	A property of materials through which one cannot see at all.
Soft	A property of materials that can be easily compressed or scratched.
Soluble	A property of materials that completely dissolve or disappear when mixed in water.
Terracotta	Clay that has been baked in a kiln.
Translucent	A property of materials through which objects can be seen, but not clearly.
Transparent	A property of materials through which things can be seen clearly.
Volume	The amount of space occupied by matter. It is measured in litres (L), millilitres (mL), and cubic metres (m³).