Answers to Learning Enhancement Activities from Chapter: Materials Around Us
1. Visit your kitchen and observe how edibles are organized. Suggest a better sorting method.
In many kitchens, items are sorted by size or usage. A better method could be:
- Dry Ingredients (e.g., spices, flour, sugar) in airtight jars arranged by usage frequency.
- Liquid Ingredients (e.g., oils, sauces) kept together in bottles to prevent spillage.
- Perishable Items (e.g., fruits, vegetables) stored in separate sections of the refrigerator.
2. Unscramble the letters and match them with their properties.
| Column I (Unscrambled Words) | Column II (Properties) |
|---|---|
| T R E M A T (MATTER) | Occupies space and has mass |
| U L S B E L O (SOLUBLE) | Mixes completely in water |
| T N E R P A S N A R T (TRANSPARENT) | Objects can be seen clearly through it |
| E R U S T L (LUSTRE) | Shiny surface |
3. Why are containers used in shops and homes usually transparent?
Transparent containers allow users to see the contents inside without opening them, making it easier to identify items and check their quantities.
4. True/False Statements
| Statement | True/False | Corrected Statement (if False) |
|---|---|---|
| (i) Wood is translucent while glass is opaque. | False | Wood is opaque, and glass is transparent. |
| (ii) Aluminium foil has lustre while an eraser does not. | True | N/A |
| (iii) Sugar dissolves in water whereas sawdust does not. | True | N/A |
| (iv) An apple is a matter because it occupies no space and has mass. | False | An apple is matter because it occupies space and has mass. |
5. Materials used to make chairs fulfilling desirable properties
| Property | Best Material |
|---|---|
| Hardness | Iron, Cement |
| Lightweight | Plastic, Bamboo |
| Does not feel cold during winters | Wood, Plastic |
| Can be cleaned regularly | Plastic, Iron (with proper coating) |
6. Materials for different types of waste containers
| Waste Type | Material for Container | Reason |
|---|---|---|
| Food waste | Plastic or stainless steel | Durable, easy to clean, and resists corrosion |
| Broken glass | Metal | Strong, safe to contain sharp edges |
| Wastepaper | Cardboard | Lightweight, easy to handle, and recyclable |
7. Air and wooden door transparency options
Correct Option: (i) Transparent, Opaque
8. Identifying mysterious materials X and Y
- Material X: Likely sugar or salt, as it is hard and soluble in water.
- Material Y: Likely clay or rubber, as it is soft and insoluble in water.
Explanation: X does not change shape easily, indicating hardness, and dissolves in water, showing solubility. Y is soft and retains its form in water, indicating insolubility.
9. Who am I?
| Property | Answer |
|---|---|
| (a) I have lustre. | Metal (e.g., gold, silver) |
| (b) I can be easily compressed. | Sponge |
| (c) I am hard and soluble in water. | Salt or Sugar |
| (d) You cannot see clearly through me. | Frosted glass or butter paper |
| (e) I have mass and volume but you cannot see me. | Air |
10. Soluble and Insoluble Material Pairs
| Soluble Pair | Insoluble Pair |
|---|---|
| Vinegar and Water | Mustard Oil and Water |
| Glucose and Water | Wheat Flour and Water |
11. Activities for Further Learning
- Recyclable Materials: Glass, paper, plastic, and metals like aluminium can be recycled.
Example: Plastic bottles can be melted and reformed into new items. - Survey with Recyclers: Recyclers often check for durability, material type (e.g., metal or plastic), and whether the material can be easily repurposed. Items like wet cardboard or heavily mixed materials are often not purchased.
- Household Object Classification: Objects like utensils, clothes, and furniture can be grouped by their materials (metal, wood, plastic). The relationship observed is that properties like durability, flexibility, and weight influence their use.
- Create and Decorate: Example: Use discarded plastic bottles to make planters. This teaches upcycling while providing practical use. Feedback could be on stability, aesthetic appeal, and functionality.
Chapter 6: Materials Around Us – Questions and Answers
1. What is a material?
Answer:
A material is any substance used to create or make objects. Examples include wood, metal, plastic, and clay.
2. Why are materials classified?
Answer:
Materials are classified to organize them based on their properties, making it easier to study and identify patterns in their usage and characteristics.
3. What is the method of arranging objects into groups called?
Answer:
The method is called classification.
4. How can you classify materials based on their appearance?
Answer:
Materials can be classified as:
- Lustrous (shiny surface, e.g., metals like gold, copper)
- Non-lustrous (dull surface, e.g., wood, rubber)
5. What are the three categories of materials based on transparency?
Answer:
- Transparent: Materials through which we can see clearly (e.g., glass).
- Translucent: Materials through which we can partially see (e.g., frosted glass).
- Opaque: Materials through which we cannot see at all (e.g., wood).
6. Why is paper not a suitable material for making cooking utensils?
Answer:
Paper is not heat-resistant, durable, or waterproof, making it unsuitable for cooking utensils.
7. Why do we use metals for making cooking utensils?
Answer:
Metals are durable, can conduct heat efficiently, and are safe for cooking purposes.
8. What property of materials allows us to make a tumbler?
Answer:
Materials used to make tumblers must be waterproof and able to hold liquids without leaking, such as metal, plastic, or glass.
9. What is meant by “lustre” in materials?
Answer:
Lustre refers to the shiny appearance of a material, often found in metals like gold, silver, or aluminium.
10. How can you identify if a material is hard or soft?
Answer:
By pressing or scratching it:
- Hard materials (e.g., stone, iron) are difficult to compress or scratch.
- Soft materials (e.g., sponge, rubber) can be compressed or scratched easily.
11. Give examples of objects classified by hardness.
| Object | Hard/Soft |
|---|---|
| Brick | Hard |
| Eraser | Soft |
| Stone | Hard |
| Pillow | Soft |
12. How can you test whether a material is soluble in water?
Answer:
Add the material to water, stir, and observe if it dissolves completely. Soluble materials disappear, while insoluble ones remain visible.
13. Give examples of materials that are soluble and insoluble in water.
| Soluble Materials | Insoluble Materials |
|---|---|
| Salt | Sand |
| Sugar | Sawdust |
| Lemon juice | Chalk powder |
14. Why do we say water is a universal solvent?
Answer:
Water is called a universal solvent because it can dissolve a wide range of substances, including salts, sugars, and gases like oxygen.
15. What is the difference between mass and volume?
Answer:
- Mass: The quantity of matter in an object (measured in grams or kilograms).
- Volume: The space occupied by an object (measured in litres or millilitres).
16. What is matter?
Answer:
Matter is anything that occupies space and has mass.
17. What units are used to measure mass and volume?
Answer:
- Mass: Gram (g), Kilogram (kg)
- Volume: Litre (L), Millilitre (mL)
18. Why do some liquids like oil not mix with water?
Answer:
Oil is insoluble in water because it is less dense and does not bond with water molecules, forming a separate layer.
19. Give examples of transparent, translucent, and opaque materials.
| Transparent | Translucent | Opaque |
|---|---|---|
| Glass tumbler | Butter paper | Wooden board |
| Clear plastic sheet | Frosted glass | Metal sheet |
20. What property allows oxygen to dissolve in water?
Answer:
The solubility of gases allows oxygen to dissolve in water, which is vital for aquatic life.
21. How do you classify materials based on their ability to float or sink in water?
Answer:
- Float: Materials less dense than water (e.g., wood, plastic).
- Sink: Materials denser than water (e.g., stone, metal).
22. What happens when sugar is mixed with water?
Answer:
Sugar dissolves completely in water, making it a soluble material.
23. What are the properties of materials that make them useful?
Answer:
Properties like hardness, lustre, transparency, solubility, and weight determine how materials are used.
24. Why is glass used to make windows?
Answer:
Glass is transparent, allowing light to pass through while providing a barrier against the environment.
25. Why is gold considered a lustrous material?
Answer:
Gold has a natural shiny surface, which makes it attractive and classified as a lustrous metal.
26. Why are some metals non-lustrous?
Answer:
Metals like iron may lose their lustre over time due to exposure to air and moisture, leading to rust or tarnish.
27. Why do we classify materials?
Answer:
Classification helps organize materials, making it easier to study their properties and choose them for specific purposes.
28. How does mass differ from weight?
Answer:
- Mass: The amount of matter in an object, measured in kilograms (kg).
- Weight: The force of gravity acting on an object’s mass, measured in newtons (N).
29. How does the invention of plastic affect humans?
Answer:
- Boon: Plastic is lightweight, durable, and versatile.
- Bane: Plastic is non-biodegradable, leading to environmental pollution.
30. Why is air considered matter?
Answer:
Air occupies space, has mass, and can be compressed, satisfying the definition of matter.
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