1. Chapter at a Glance
Look around your classroom: a wooden desk, a steel almirah, glass windows, a plastic water bottle, a cotton bag. Each object is made of one or more materials. Why is a window made of glass and not wood? Why is a cooking pot made of steel and not plastic? The answer lies in the properties of materials. In this chapter you will learn to group materials by their properties and understand what matter is.
- Objects and the materials they are made of.
- Grouping (classifying) materials by common properties.
- Properties: appearance (lustrous or not), hardness, transparency, solubility in water, heaviness (mass) and volume.
- Matter — anything that has mass and occupies space.
2. Observing Objects Around Us
A material is any substance used to make an object. The same object can be made from different materials (a tumbler can be glass, steel or plastic), and the same material can make many objects (wood makes doors, tables, pencils and toys). We choose a material by checking whether its properties suit the job.
India has a long history of using materials skilfully. Pottery in the Ganga plains and Baluchistan dates back about 7,000–8,000 years, and the Sindhu-Sarasvatī (Harappan) civilisation used advanced pottery methods. Ayurveda described matter using twenty properties called guṇa, such as heavy–light and hard–soft.
3. How to Group Materials?
Classification is arranging objects into groups on the basis of a common property. Grouping helps us find things easily (as in a kitchen or a shop), study their properties and choose the right material for a use. One set of objects can be grouped in many ways — by shape, by material, by use or by any property.
4. Properties of Materials
(a) Appearance — lustrous or non-lustrous
Materials with a shiny surface are lustrous — most metals like gold, silver, copper, iron and aluminium (when freshly cut or polished). Materials without shine — wood, paper, cloth, chalk — are non-lustrous. Metals can lose their shine because of the action of air and moisture, but regain it when rubbed.
(b) Hardness
Hard materials are difficult to compress or scratch — iron, stone, glass, diamond. Soft materials can be compressed or scratched easily — sponge, cotton, rubber, wax.
(c) Transparency
| Type | Meaning | Examples | Uses |
|---|---|---|---|
| Transparent | Things behind can be seen clearly | Clear glass, water, air, clear plastic | Windows, spectacles, storage jars |
| Translucent | Things seen but not clearly | Butter paper, frosted glass, oily paper | Bathroom windows, lamp shades |
| Opaque | Cannot see through at all | Wood, metal, cardboard, stone | Doors, walls, almirahs |
(d) Solubility in water
Substances that disappear completely when stirred in water are soluble — sugar, salt, lemon juice (mixes), vinegar. Those that do not mix and can be seen even after stirring are insoluble — sand, chalk powder, sawdust, oil. Some liquids, like oil, form a separate layer over water.
(e) Heavy or light — mass
Mass is the amount of matter in an object; it tells whether an object is heavier or lighter. The SI unit of mass is the kilogram (kg). Two cups of the same size can have very different masses if they are made of different materials (steel versus paper).
(f) Space and volume
Every object takes up some space. The space occupied by matter is its volume. The SI unit of volume is the cubic metre (m³); in daily life we use litres and millilitres. Even air occupies space — a blown balloon shows this.
5. What is Matter?
Matter is anything that occupies space and has mass. Wood, water, air, milk, stone and our own bodies are all matter. Light, sound, heat and feelings like happiness are not matter, because they have no mass and do not occupy space.
Which material is best for making a classroom chair: glass, wood or cloth? A chair must be strong, hard, not too heavy and safe. Glass is hard but breaks easily and is dangerous; cloth is too soft. Wood (or strong plastic/metal) is the best choice.
Material X does not dissolve in water and cannot be scratched by a nail. Material Y dissolves in water. X could be a stone or glass piece (hard, insoluble); Y could be sugar or salt (soluble).
6. Master Table: Key Terms
| Term | Meaning |
|---|---|
| Material | Substance used to make an object |
| Classification | Grouping objects by a common property |
| Lustrous | Shiny surface (mostly metals) |
| Hard / Soft | Difficult / easy to compress or scratch |
| Transparent / Translucent / Opaque | See clearly / partly / not at all |
| Soluble / Insoluble | Disappears in water / does not |
| Mass | Amount of matter; SI unit kilogram (kg) |
| Volume | Space occupied; SI unit cubic metre (m³) |
| Matter | Anything that has mass and occupies space |
7. Master Summary Table
| Property | Group A | Group B | Use in daily life |
|---|---|---|---|
| Appearance | Lustrous: copper, gold | Non-lustrous: wood, paper | Jewellery from lustrous metals |
| Hardness | Hard: iron, stone | Soft: cotton, sponge | Tools vs pillows |
| Transparency | Transparent: glass | Opaque: wood | Windows vs doors |
| Solubility | Soluble: sugar, salt | Insoluble: sand, chalk | Making sherbet vs filtering sand |
| Mass | Heavy: iron ball | Light: thermocol | Packing material |
8. Mind Map
- Common property
- Easy to find and study
- Lustrous / non-lustrous
- Hard / soft
- Transparent, translucent, opaque
- Soluble / insoluble
- Mass (kg)
- Volume (m³)
9. Tips and Tricks
- T–T–O ladder: Transparent (all light) → Translucent (some) → Opaque (none).
- For “Is it matter?” questions ask two things: does it have mass? does it take up space? Both yes → matter.
- For “choose a material” questions, list the property needed first, then pick the material.
- Saying air is not matter — air has mass and occupies space.
- Calling frosted glass transparent — it is translucent.
- Thinking all hard things are heavy — a hard plastic ruler is light.
10. Important One-liners
- A material is any substance used to make an object.
- Metals are generally lustrous.
- Diamond is one of the hardest materials; cotton is soft.
- Clear glass is transparent; butter paper is translucent; wood is opaque.
- Sugar and salt are soluble; sand and chalk are insoluble in water.
- The SI unit of mass is the kilogram.
- The SI unit of volume is the cubic metre.
- Matter has mass and occupies space; light and sound are not matter.
11. Exam-pattern Questions with Detailed Answers
Which material is translucent?
- Clear glass
- Butter paper
- Wood
- Iron sheet
Show answer
Through butter paper we can see objects but not clearly. Clear glass is transparent; wood and iron are opaque.
Answer: (B) Butter paper
Define matter.
Show answer
Anything that has mass and occupies space is called matter.
Answer: Anything with mass that occupies space
Name two soluble and two insoluble substances.
Show answer
Soluble: sugar, salt. Insoluble: sand, chalk powder.
Answer: Sugar, salt; sand, chalk
Why are food grains often stored in transparent containers in shops?
Show answer
Transparent containers let shopkeepers and customers see what is inside and how much is left without opening them, which saves time and keeps food clean.
Answer: Contents are visible without opening
True or False (correct if false): All metals are soft.
Show answer
False. Most metals, like iron, are hard. (Some, like sodium, are soft, but this is an exception.)
Answer: False — most metals are hard
Which of these are not matter: air, sunlight, water vapour, sound, smell of perfume?
Show answer
Sunlight and sound have no mass and do not occupy space, so they are not matter. Air, water vapour and perfume particles (which cause smell) are matter.
Answer: Sunlight and sound
Suggest a suitable material for: (a) a window pane, (b) a cooking pot, (c) a raincoat. Give the property used.
Show answer
(a) Glass — transparent. (b) Steel or aluminium — hard, does not melt or burn easily and conducts heat. (c) Plastic or rubber-coated cloth — waterproof.
Answer: Glass; steel; plastic
Two cups of the same size, one of steel and one of paper, are weighed. Which is heavier and why?
Show answer
The steel cup is heavier because steel has more mass for the same size than paper. Mass depends on the material, not just the size.
Answer: Steel cup — more mass for the same size
“Who am I?” I am shiny, hard and do not dissolve in water. I conduct heat and make cooking utensils.
Show answer
Lustrous, hard, insoluble and used for utensils — a metal such as steel (iron alloy) or aluminium.
Answer: A metal like steel or aluminium
Which container would you use to collect wet kitchen waste: paper box, cloth bag or plastic/metal bin? Justify.
Show answer
A plastic or metal bin with a lid: it is waterproof (does not get soggy like paper or leak like cloth), easy to clean and keeps smells and flies away.
Answer: Lidded plastic or metal bin — waterproof and cleanable
Light passes through air but not through a wooden door. Classify these and give one use of each property.
Show answer
Air is transparent — lets light reach everything in a room. A wooden door is opaque — gives privacy and blocks sunlight.
Answer: Air transparent; wood opaque
12. Quick Revision Summary
- Objects are made of materials; we choose materials by their properties.
- Classification = grouping by a common property.
- Properties: lustre, hardness, transparency (transparent/translucent/opaque), solubility, mass, volume.
- Mass: SI unit kg; volume: SI unit m³.
- Matter has mass and occupies space; light and sound are not matter.