Exercise Solutions Available
Step-by-step answers for all textbook questions in this chapter
Sorting Materials into Groups: NCERT Exercise Solutions
How to Use This Page
This page provides complete NCERT exercise solutions for Class 6 Science Chapter 4 — Sorting Materials into Groups. Work through each question independently before checking the answers below. The solutions follow the NCERT textbook style and include practical examples, tables, and clear explanations to help you understand every concept thoroughly.
Tips for best results:
- Learn the definitions in the Key Concepts table — they are frequently tested.
- Practice grouping objects by different properties (appearance, hardness, solubility, transparency).
- Understand the difference between transparent, translucent, and opaque with real-life examples.
- Use the Exam Checklist before your exam to make sure you have not missed any topic.
Key Concepts (Quick Recap)
| Term | Definition |
|---|---|
| Classification | The process of sorting or grouping objects or materials based on their common properties. Classification helps us study and understand materials systematically. |
| Objects | Things that can be seen and touched. An object is made from one or more materials. For example, a chair is an object made of wood, metal, or plastic. |
| Materials | The substances from which objects are made. For example, glass, wood, iron, plastic, and cotton are materials. A single object may be made of multiple materials. |
| Hardness | The property of a material that describes how difficult it is to scratch or dent it. Hard materials cannot be easily scratched (iron, diamond). Soft materials can be easily scratched (soap, sponge, chalk). |
| Solubility | The property of a substance that describes whether it can dissolve in a liquid (usually water). Soluble substances dissolve; insoluble substances do not. |
| Transparent | Materials that allow light to pass through them completely, so we can see through them clearly. Examples: glass, clear water, cellophane, clear plastic. |
| Translucent | Materials that allow only some light to pass through them. We can see through them partially but not clearly. Examples: frosted glass, wax paper, butter paper, muddy water. |
| Opaque | Materials that do not allow any light to pass through them. We cannot see through them at all. Examples: wood, metal, cardboard, stone, rubber. |
| Metals | Materials that are typically hard, shiny, malleable, ductile, and good conductors of heat and electricity. Examples: iron, copper, gold, silver, aluminium. |
| Non-metals | Materials that are typically not shiny, not malleable, not ductile, and poor conductors of heat and electricity. Examples: wood, plastic, rubber, glass, sulphur. |
| Solution | A homogeneous mixture formed when a soluble substance dissolves completely in a liquid. For example, salt dissolved in water forms a salt solution. |
| Miscible | Liquids that mix completely with each other. For example, water and vinegar are miscible. |
| Immiscible | Liquids that do not mix with each other and form separate layers. For example, oil and water are immiscible. |
| Density | The mass of a material per unit volume. Materials with lower density than water float; those with higher density sink. |
| Conductivity | The ability of a material to allow heat or electricity to pass through it. Metals are good conductors; wood and plastic are poor conductors (insulators). |
Intext Questions and Answers
Question 1. Name five objects that can be made from: (a) Wood (b) Paper (c) Leather (d) Plastic (e) Metal
(a) Objects made from wood: 1. Chair 2. Table 3. Door 4. Pencil 5. Cricket bat
(b) Objects made from paper: 1. Notebook 2. Newspaper 3. Cardboard box 4. Paper cup 5. Tissue paper
(c) Objects made from leather: 1. Shoes 2. Belt 3. Bag 4. Wallet 5. Jacket
(d) Objects made from plastic: 1. Water bottle 2. Bucket 3. Toy 4. Pen 5. Comb
(e) Objects made from metal: 1. Utensil (cooking vessel) 2. Nail 3. Coin 4. Key 5. Needle
Key observation: The same material can be used to make different objects, and the same object can be made from different materials (e.g., a chair can be made of wood, metal, or plastic). This is why we study materials — their properties determine what objects they can be used for.
Question 2. Group the following objects based on the material they are made of: book, tumbler, chair, paper, rubber band, ball, plate, nail, steel spoon, cotton shirt
| Material | Objects Made From It |
|---|---|
| Wood | Chair |
| Paper | Book |
| Glass | Tumbler (glass) |
| Rubber | Rubber band, ball (rubber ball) |
| Steel/Metal | Plate (steel plate), nail, steel spoon |
| Cotton | Cotton shirt |
Note: Some objects can be made from different materials. For example, a tumbler can be made of glass, plastic, or steel. A plate can be made of steel, ceramic, or plastic. A ball can be made of rubber, plastic, or leather.
Question 3. Match the objects given in Column I with the materials given in Column II.
| Column I (Objects) | Column II (Materials) |
|---|---|
| (i) Newspaper | (a) Leather |
| (ii) Walking stick | (b) Glass |
| (iii) Tumbler | (c) Wood |
| (iv) Belt | (d) Paper |
| Column I (Objects) | Column II (Materials) |
|---|---|
| (i) Newspaper | (d) Paper |
| (ii) Walking stick | (c) Wood |
| (iii) Tumbler | (b) Glass |
| (iv) Belt | (a) Leather |
Newspapers are made from paper. Walking sticks are traditionally made from wood. Tumblers (drinking glasses) are commonly made from glass. Belts are made from leather.
Question 4. State whether the following statements are true or false:
(a) A stone is transparent. (b) A notebook has the same transparency as a glass tumbler. (c) A wood board is opaque. (d) A glass tumbler is transparent. (e) We can see through a sheet of butter paper.
(e) True (partially) — Butter paper is translucent. We can see through it partially but not clearly. Some light passes through, but the image is not sharp.
Question 5. Group the following as transparent, translucent, or opaque: glass, wood, butter paper, clear water, sheet of cardboard, wax paper, sheet of thermocol, oil paper, ceramic plate, frosted glass
| Transparent (light passes through completely) | Translucent (light passes through partially) | Opaque (no light passes through) |
|---|---|---|
| Glass | Butter paper | Wood |
| Clear water | Wax paper | Sheet of cardboard |
| Oil paper | Sheet of thermocol | |
| Frosted glass | Ceramic plate |
- Transparent: Glass and clear water allow us to see through them clearly. We can read text through a glass pane or through clear water.
- Translucent: Butter paper, wax paper, oil paper, and frosted glass allow some light to pass through but we cannot see clearly through them. We can see a blurred image or just light and shadows.
- Opaque: Wood, cardboard, thermocol, and ceramic plate do not allow any light to pass through. We cannot see anything through them at all.
Question 6. Which of the following materials are soluble in water? Salt, sawdust, sugar, sand, chalk powder, vinegar, lemon juice, copper sulphate, oxygen
| Substance | Soluble or Insoluble | Observation |
|---|---|---|
| Salt | Soluble | Dissolves completely in water to form a salt solution |
| Sawdust | Insoluble | Floats on water or sinks but does not dissolve |
| Sugar | Soluble | Dissolves completely in water to form a sugar solution |
| Sand | Insoluble | Settles at the bottom; does not dissolve |
| Chalk powder | Insoluble | Does not dissolve; forms a suspension that settles |
| Vinegar | Soluble | Mixes completely with water (miscible liquid) |
| Lemon juice | Soluble | Mixes completely with water |
| Copper sulphate | Soluble | Dissolves in water to form a blue solution |
| Oxygen | Soluble (slightly) | Dissolves in small amounts — this dissolved oxygen is essential for aquatic life |
Key point: Some substances dissolve completely (soluble), while others do not dissolve at all (insoluble). Gases like oxygen dissolve only in small amounts in water but this dissolved oxygen is crucial for fish and other aquatic organisms.
Question 7. You are given a mixture of salt and sand. How will you separate them?
1. Add water: Add water to the mixture of salt and sand and stir well. Salt is soluble in water and will dissolve. Sand is insoluble and will not dissolve.
2. Filter: Pour the mixture through filter paper. The salt solution (salt dissolved in water) passes through as the filtrate. The sand remains on the filter paper as the residue.
3. Evaporate the filtrate: Heat the filtrate (salt solution) in a beaker. The water evaporates, leaving behind the salt as a white solid.
4. Dry the residue: The sand on the filter paper can be dried in the sun or on a hot plate.
Question 8. Why do we need to classify materials or objects into groups?
1. Easy identification: Classification helps us find and identify objects quickly. For example, in a library, books are classified by subject so we can find what we need easily.
2. Study of properties: When objects with similar properties are grouped together, it is easier to study their common properties. For example, all metals share properties like shine, hardness, and conductivity.
3. Predicting behaviour: If we know the group an object belongs to, we can predict how it will behave. For example, if we know an object is made of metal, we can predict it will conduct heat and electricity.
4. Choosing appropriate materials: Classification helps us choose the right material for a particular use. For example, transparent materials (glass) are used for windows; hard materials (iron) are used for building.
5. Systematic organisation: Without classification, it would be impossible to study the millions of different materials and objects around us in an organised manner.
6. Comparison: Grouping makes it easy to compare objects. For example, comparing the properties of metals versus non-metals helps us understand their differences.
Exercise Questions and Answers
Question 1. Name five materials that are: (a) Shiny (b) Not shiny
(a) Shiny materials (lustrous): 1. Iron 2. Gold 3. Copper 4. Aluminium 5. Silver
These are all metals. Metals have a shiny surface called lustre. When freshly cut or polished, metals have a bright, reflective surface.
(b) Not shiny materials (non-lustrous): 1. Wood 2. Rubber 3. Chalk 4. Cardboard 5. Plastic
These are non-metals or non-metallic materials. They do not have a shiny surface even when polished.
Note: Some non-metals like iodine and graphite are shiny, but this is an exception. Generally, metals are shiny and non-metals are not.
Question 2. What are metals? Give four examples.
- They are hard (cannot be easily scratched or cut)
- They are shiny (lustrous) when freshly polished
- They are malleable (can be beaten into thin sheets)
- They are ductile (can be drawn into thin wires)
- They are good conductors of heat and electricity
- They produce a ringing sound when hit (sonorous)
Four examples of metals: 1. Iron — used for making bridges, utensils, nails, and construction materials 2. Copper — used for making electrical wires, utensils, and coins 3. Aluminium — used for making foil, window frames, and aeroplane bodies 4. Gold — used for making jewellery and ornaments
Other examples: Silver, zinc, lead, tin, magnesium, sodium.
Question 3. What are non-metals? Give four examples.
- They are not shiny (non-lustrous) — exceptions like iodine and graphite exist
- They are softer than metals (many can be easily scratched or broken)
- They are not malleable — they break when hammered
- They are not ductile — they cannot be drawn into wires
- They are poor conductors of heat and electricity (exception: graphite conducts electricity)
- They are not sonorous — they do not produce a ringing sound when hit
Four examples of non-metals: 1. Sulphur — a yellow powder used in making matches, fireworks, and vulcanisation of rubber 2. Carbon — exists as diamond, graphite, and coal; used in pencils (graphite) and as fuel (coal) 3. Oxygen — a gas essential for breathing and combustion 4. Phosphorus — used in matchboxes, fireworks, and fertilisers
Other examples: Nitrogen, chlorine, bromine, helium, neon.
Question 4. Classify the following as metals or non-metals: Iron, sulphur, aluminium, carbon, copper, oxygen, gold, phosphorus
| Material | Classification | Reasoning |
|---|---|---|
| Iron | Metal | Hard, shiny, malleable, ductile, good conductor |
| Sulphur | Non-metal | Not shiny (yellow powder), brittle, poor conductor |
| Aluminium | Metal | Shiny, malleable (foil), ductile, good conductor |
| Carbon | Non-metal | Exists as graphite (soft, black) or diamond (hard, shiny); brittle in most forms |
| Copper | Metal | Shiny (reddish-brown), malleable, ductile, excellent conductor |
| Oxygen | Non-metal | Colourless gas, poor conductor, not malleable or ductile |
| Gold | Metal | Very shiny (yellow), highly malleable, ductile, good conductor |
| Phosphorus | Non-metal | Not metallic, exists as white or red solid, poor conductor |
Question 5. Which of the following materials floats on water?
(A) Iron nail (B) Cotton ball ✓ (C) Stone (D) Coin
A cotton ball floats on water because cotton traps air in its fibres, making its overall density lower than water. An iron nail, stone, and coin all sink because they have higher density than water.
Note: Whether an object floats or sinks depends on its density relative to water. Objects with density less than water (like wood, cork, cotton, ice) float. Objects with density more than water (like iron, stone, coin) sink. However, a soaked cotton ball that has absorbed water may eventually sink.
Question 6. Choose the correct option:
Which of the following is transparent?
(A) Wood (B) Cardboard (C) Glass ✓ (D) Metal sheet
Glass is transparent — it allows light to pass through completely, and we can see through it clearly. Wood, cardboard, and metal sheets are all opaque — no light passes through them.
Question 7. Group the following materials on the basis of hardness: sponge, iron nail, chalk, diamond, rubber band, stone
| Hard Materials | Soft Materials |
|---|---|
| Iron nail | Sponge |
| Diamond | Chalk |
| Stone | Rubber band |
Hard materials are those that cannot be easily compressed, scratched, or cut. Iron nail, diamond, and stone are hard. Diamond is the hardest known natural material.
Soft materials are those that can be easily compressed, scratched, or cut. Sponge, chalk, and rubber band are soft. A sponge can be compressed easily, chalk can be scratched with a fingernail, and a rubber band can be stretched.
Note: Hardness is relative. For example, a stone is hard compared to a sponge but soft compared to a diamond.
Question 8. Explain why the following are grouped together: (a) Copper, silver, gold (b) Wood, plastic, rubber
(a) Copper, silver, gold are grouped together because they are all metals. They share common metallic properties:
- They are shiny (lustrous) and have a bright, reflective surface.
- They are malleable — they can be beaten into thin sheets. Gold is the most malleable metal.
- They are ductile — they can be drawn into thin wires. Copper is highly ductile and is used for electrical wires.
- They are good conductors of heat and electricity. Silver is the best conductor, followed by copper and gold.
- They are hard (though gold is relatively soft among metals).
- They are sonorous — they produce a ringing sound when struck.
(b) Wood, plastic, rubber are grouped together because they are all non-metals (or non-metallic materials). They share common non-metallic properties:
- They are not shiny (non-lustrous) — they have a dull appearance.
- They are not malleable — they break or crack when hammered.
- They are not ductile — they cannot be drawn into wires.
- They are poor conductors of heat and electricity — they are insulators.
- They are not sonorous — they do not produce a ringing sound when struck.
- They can be soft or hard but are generally softer than metals.
Multiple Choice Questions (MCQ) for Practice
Q1. Which property of a material decides whether it will float or sink in water?
(A) Transparency (B) Hardness (C) Density ✓ (D) Solubility
Q2. Which of the following is a good conductor of electricity?
(A) Wood (B) Plastic (C) Rubber (D) Copper ✓
Q3. Which material is used for making windows because it is transparent?
(A) Wood (B) Metal (C) Glass ✓ (D) Rubber
Q4. Which of the following substances is insoluble in water?
(A) Salt (B) Sugar (C) Sand ✓ (D) Vinegar
Q5. A material through which we can see clearly is called:
(A) Opaque (B) Translucent (C) Transparent ✓ (D) None of these
Q6. Which of the following is a property of metals?
(A) They are non-lustrous (B) They are poor conductors of heat (C) They are ductile ✓ (D) They are soft
Q7. Oil and water form two separate layers because they are:
(A) Soluble (B) Miscible (C) Immiscible ✓ (D) Transparent
Q8. Which of the following will sink in water?
(A) Cork (B) Wood (C) Ice (D) Iron nail ✓
Common Mistakes to Avoid
1. Confusing transparent, translucent, and opaque: Remember the key distinction: Transparent = can see through clearly (glass, clear water). Translucent = can see through partially, image is blurred (butter paper, frosted glass). Opaque = cannot see through at all (wood, metal, cardboard). Do not confuse translucent with transparent.
2. Thinking all soft materials float and all hard materials sink: Hardness and floating/sinking are different properties. A hard iron nail sinks because it is dense, while soft wood floats because it is less dense than water. Do not link hardness with floating ability — it depends on density.
3. Confusing miscible/immiscible with soluble/insoluble: Soluble/insoluble refers to a solid dissolving in a liquid (salt is soluble in water, sand is insoluble). Miscible/immiscible refers to a liquid mixing with another liquid (vinegar is miscible with water, oil is immiscible). Use the correct term for the correct situation.
4. Assuming all non-metals are soft and brittle: While most non-metals are soft and brittle, there are important exceptions. Diamond (a form of carbon) is the hardest natural substance. Graphite (another form of carbon) is a good conductor of electricity. Always mention these exceptions when discussing non-metal properties.
5. Forgetting that classification can be done in multiple ways: The same set of objects can be grouped differently based on different properties. For example, a group of objects can be classified by appearance (shiny/dull), hardness (hard/soft), solubility (soluble/insoluble), or transparency (transparent/translucent/opaque). Always check which property is being used for classification.
Exam Checklist
Before your exam, make sure you can answer "Yes" to each of the following:
- [ ] I can explain why we classify materials and give at least three reasons for classification.
- [ ] I can list at least five properties of materials (appearance, hardness, solubility, transparency, conductivity) with examples.
- [ ] I can classify any given material as transparent, translucent, or opaque with reasoning.
- [ ] I can identify whether a substance is soluble or insoluble in water and explain miscible vs. immiscible liquids.
- [ ] I can differentiate between metals and non-metals with at least four properties and examples of each.
- [ ] I can explain why certain materials are used for specific purposes (e.g., copper for wires, glass for windows, cotton for summer clothes).
- [ ] I can group a given set of objects or materials based on different properties (hardness, solubility, transparency, etc.).
- [ ] I can define and give examples of key terms: classification, lustrous, opaque, translucent, transparent, soluble, insoluble, miscible, immiscible, ductile, malleable, sonorous.