1. Introduction to Materials and Objects

Every object we see around us is created from one or more substances. Any substance used to create an object is called a material. Science helps us understand that:

• An object is the final item (e.g., a chair, a pot, or a pencil).
• A material is what it is made of (e.g., wood, clay, or lead).
• A single object can be made using multiple materials (e.g., a pen made of plastic, metal, and ink).
• A single material can be used to make different types of objects (e.g., iron used for nails, gates, and utensils).

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Historical Perspective: Indian Pottery

India has a sophisticated history of material science, specifically in pottery production:

• The earliest pottery in the Indian subcontinent dates back $7,000$ to $8,000$ years in the Ganga plains (Lahuradewa).
• The Sindhu-Sarasvatī (Harappan) Civilisation ($2600-1900$ BCE) excelled in:
  • Wheel-turned pottery.
  • Applying decorative coats called ‘slips’.
  • Creating Terracotta (baked clay) items for cooking and storage.

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Object	Primary Material
Notebook	Paper
Tumbler	Glass / Steel
Crucible	Clay / Iron
Pot	Terracotta (Baked Clay)

2. Classification and Grouping of Materials

The world is full of diverse objects. To study them effectively, we use Classification, which is the method of arranging objects into groups based on common properties.

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How do we choose a Material?

We do not choose materials randomly. The selection depends on two main factors:

1. Properties of the Material: Does it have the required strength, texture, or ability?
2. Purpose of the Object: What will the object be used for?

Consider these examples of purpose-driven selection:

• Tumbler: Must be made of materials like glass, plastic, or metal that can hold water. A cloth tumbler would be useless for storing liquids.
• Cooking Utensils: Must be made of heat-resistant materials like metals. Using paper would result in the utensil burning.
• Sports Equipment: Balls for different sports (Cricket vs. Tennis) are made of different materials to achieve specific bounce levels and durability.

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3. Physical Properties: Appearance and Hardness

Materials are often classified based on their Physical Appearance (how they look) and their Texture/Hardness (how they feel).

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Appearance: Lustre

Materials that have a shiny surface are said to have Lustre. This is a primary characteristic of Metals.

• Lustrous Materials: Iron, Copper, Aluminium, and Gold.
• Non-lustrous Materials: Paper, Wood, Rubber, and Jute.
• Important Note: Metals may lose their shine and look dull when exposed to air and moisture. Therefore, we should check for lustre on freshly cut surfaces.
• Caution: "All that glitters is not gold"—materials can be made shiny through polishing or plastic coatings, which does not make them metals.

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Hardness and Compressibility

Hardness refers to how difficult it is to scratch or compress a material.

• Soft Materials: Can be easily compressed or scratched (e.g., Sponge, Eraser, Candle, Chalk).
• Hard Materials: Are difficult to compress or scratch (e.g., Stone, Iron, Brick).
• Relative Nature: Hardness is relative. For instance, Rubber is harder than sponge but softer than iron.

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Property Classification Table

Material	Gold Ornament	Wooden Log	Sponge	Iron Key	Chalk
Appearance	Lustrous	Dull	Dull	Lustrous (if new)	Dull
Hardness	Hard	Hard	Soft	Hard	Soft

4. Transparency: Seeing Through Materials

The property of a material that allows us to see through it is known as transparency. Based on this, matter is divided into three categories:

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Types of Materials Based on Light Transmission

1. Transparent Materials:
   • These allow light to pass through completely.
   • We can see through them clearly.
   • Examples: Glass, clear water, air, and cellophane paper.
2. Opaque Materials:
   • These do not allow any light to pass through.
   • We cannot see through them at all.
   • Examples: Wooden boards, cardboard, and metal sheets.
3. Translucent Materials:
   • These allow light to pass through partially.
   • We can see through them, but not clearly (hazy view).
   • Examples: Butter paper, frosted glass, and oily paper.

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Understanding these properties helps us in daily activities, like playing hide and seek or choosing the right material for window panes in Indian homes.

5. Solubility in Water

Water is known as a universal solvent because of its remarkable ability to dissolve a wide variety of substances. This property is essential for the survival of living organisms, including the transport of nutrients in our blood and the survival of aquatic life.

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Classification based on Solubility

Substances behave differently when mixed with water. We can classify them as follows:

• Soluble Materials: These are substances that completely disappear or dissolve when stirred in water.
  • Examples: Common salt, sugar, honey, and lemon juice.
• Insoluble Materials: These are substances that do not mix with water and remain visible even after being stirred for a long time.
  • Examples: Sand, sawdust, chalk powder, pebbles, and mustard oil.

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Solubility of Liquids and Gases

It is not just solids that dissolve in water. Many liquids and gases also interact with water:

• Liquids: Some liquids like vinegar and lemon juice mix completely with water. Others, like coconut oil or kerosene, form a separate layer on top of the water.
• Gases: Oxygen gas is slightly soluble in water. This dissolved oxygen is extremely important for the survival of fish and other aquatic plants and animals.

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Material	Behavior in Water (On Stirring)	Inference
Sugar	Disappears completely	Soluble
Sand	Settles at the bottom	Insoluble
Chalk Powder	Makes water cloudy and settles	Insoluble
Salt	Disappears completely	Soluble
Sawdust	Floats on the surface	Insoluble
Observation	Stirring result	Solubility status

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Indian Perspective: Shikanji and ORS

In Indian households, the property of solubility is used to prepare refreshing drinks and medicine:

• Shikanji (Lemonade): A mixture of sugar, salt, and lemon juice in water where all ingredients dissolve to create a uniform taste.
• ORS (Oral Rehydration Solution): A life-saving mixture used to treat dehydration.

The standard formula for Home-made ORS involves:

1. $1 \text{ Litre}$ of boiled and cooled water.
2. $6 \text{ teaspoons}$ of Sugar.
3. $0.5 \text{ teaspoon}$ of Common Salt.

6. Understanding Matter: Mass and Volume

Everything we see, touch, or feel in our surroundings is composed of Matter. Matter is anything that has mass and occupies space. This includes everything from the Himalayas to the tiny grains of sand in Rajasthan.

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Mass: The Quantity of Matter

The property that tells us how heavy or light an object is refers to its mass. In scientific terms, mass gives the actual quantity of matter present in an object.

• SI Unit: The International System of Units uses kilogram ($kg$) as the standard unit for mass.
• Smaller Units: For smaller quantities, gram ($g$) and milligram ($mg$) are used.
• Rules for Writing: Always leave a space between the number and the unit. For example, write $5 \text{ kg}$ and not $5\text{kg}$. Also, symbols are never written in plural (avoid $5 \text{ kgs}$).

$\text{Formula: } 1 \text{ kg} = 1000 \text{ g}$

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Volume: The Space Occupied

Every object, whether solid, liquid, or gas, occupies some space. This space is called its volume.

• SI Unit: The standard unit for volume is the cubic metre ($m^3$).
• Liquid Measurements: In daily life, we measure liquids in Litres ($L$) and millilitres ($mL$).
• Relation between Units:
  • $1 \text{ L} = 1000 \text{ mL}$
  • $1 \text{ m}^3 = 1000 \text{ L}$

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Why is Classification of Matter Useful?

Grouping materials based on mass and volume helps us observe patterns and organize our life. For instance:

• Grocers: Organize items by mass (pulses and grains in $kg$).
• Milkmen: Measure volume in litres ($L$).
• Chemists: Group medicines according to their chemical properties and state of matter.

7. Ancient Indian Perspective (Ayurveda)

Centuries before modern science categorized materials, ancient Indian scholars had developed a highly sophisticated system of classification of physical matter. This is primarily documented in Ayurveda, the traditional Indian system of medicine.

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The Concept of 20 Guṇas (Properties)

The Aṣhtanga hṛidaya Sūtra sthāna 1.18 mentions $20$ properties or Guṇas. These properties are arranged in ten pairs of opposites. They are used to describe the nature of all physical matter, food, plants, animals, and the human body.

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Sanskrit Term (Pair A)	English Meaning	Sanskrit Term (Pair B)	English Meaning
Guru	Heavy	Laghu	Light
Manda	Slow	Tīkṣhṇa	Sharp / Quick
Hima	Cold	Uṣhṇa	Hot
Snigdha	Oily / Unctuous	Rukṣha	Dry
Śhlakṣhaṇa	Smooth	Khara	Rough
Sāndra	Solid / Dense	Drava	Liquid / Fluid
Mṛidu	Soft	Kaṭhina	Hard
Sthira	Stable / Static	Khāla / Sara	Unstable / Moving
Sūkṣhma	Subtle / Small	Sthūla	Gross / Big
Viśhada	Clear / Non-slimy	Picchhila	Sticky / Slimy

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Significance of this Classification

This ancient system allows us to understand the world in a very practical way:

• Food: We classify food as Guru (heavy to digest) or Laghu (light to digest).
• Environment: Weather can be described as Hima (cold) or Uṣhṇa (hot).
• Medical Treatment: Ayurveda uses the law of opposites. For example, a dry (Rukṣha) skin condition is treated with an oily (Snigdha) material.

By studying these properties, we can conclude that classification of the non-living world is as important as the classification of the living world to maintain balance and health.

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