📘 Class 7 General Science – Unit 4: Metals and Non-metals (Textbook Solutions, Pages 120–152)
This post gives complete Class 7 AP SCERT General Science Unit 4 "Metals and Non-metals" solutions for pages 120 to 152, covering all questions from the "Let us Enhance our Learning" exercise. Students preparing for AP SCERT Class 7 Science exams, CBSE/State Board science worksheets, and Metals and Non-metals important questions and answers will find easy, exam-ready answers here — including definitions of malleability, ductility, sonority, corrosion and rusting, MCQs, matching questions, true/false statements, and short essay-type answers explained in simple language for kids. Perfect for APTET aspirants, teachers preparing worksheets, and Class 7 students revising Chapter 4 Science.
📝 Let us Enhance our Learning (Page 148–152)
Q1. Define the following.
A) Malleability: The property of a material by which it can be beaten into thin sheets is called malleability.
B) Ductility: The property of a material by which it can be drawn into thin wires is called ductility.
C) Sonority: The property of metals by which they produce a ringing sound when struck is called sonority.
D) Corrosion: The gradual deterioration (damage) of a metal surface caused by air, water, or other substances is called corrosion.
E) Rusting: The formation of a brown deposit (hydrated iron oxide) on iron objects, due to the combined action of oxygen and moisture, is called rusting.
Q2. Write two properties each for metals and non-metals.
Metals: (i) Metals are generally lustrous (shiny). (ii) Metals are malleable and ductile — they can be beaten into sheets and drawn into wires.
Non-metals: (i) Non-metals are usually non-lustrous (dull) and brittle. (ii) Non-metals are poor conductors of heat and electricity.
Q3. A substance can be drawn into long wires used for electrical purposes. What property/properties does that substance show?
Answer: D — both ductility and conductance of electricity
Q4. Which of the following metal catches fire when it comes in contact with water?
Answer: D — Sodium
Q5. Why are only a few metals suitable for making jewellery?
Only a few metals like gold, silver and platinum are used for making jewellery because they are highly malleable and ductile (can be shaped into fine designs and thin wires), lustrous (shiny in appearance), and they do not corrode or lose their shine easily when exposed to air and water. Most other metals rust, corrode, or lose their shine over time, so they are not suitable for jewellery.
Q6. What happens when oxygen reacts with magnesium and sulphur? What are the main differences in the nature of products formed?
When magnesium burns in oxygen, it forms magnesium oxide (a white powder):
Magnesium + Oxygen → Magnesium Oxide
When sulphur burns in oxygen, it forms sulphur dioxide gas:
Sulphur + Oxygen → Sulphur Dioxide
Main difference: Magnesium oxide (a metal oxide) dissolves in water to form magnesium hydroxide, which is basic in nature (turns red litmus blue). Sulphur dioxide (a non-metal oxide) dissolves in water to form sulphurous acid, which is acidic in nature (turns blue litmus red). In general, metal oxides are basic while non-metal oxides are acidic.
Q7. An ironsmith heats iron before making tools. Why is heating necessary in this process?
When iron is heated, it becomes red hot and soft, so its malleability increases. This makes it much easier for the ironsmith to beat and shape the hot iron into tools like axes, spades and tongs. If the iron is not heated, it would be too hard to bend or shape.
Q8. Students made statements about magnesium oxide solution. Whose statement/s is/are correct?
Amar: It is basic. Turns red litmus blue. | Nandu: It is acidic. Turns blue litmus red.
Answer: A — Only Amar (Magnesium oxide is a metal oxide, so it is basic in nature and turns red litmus paper blue.)
Q9. Which metal is commonly used to make food packaging materials as it is cheaper, and its thin sheets can be folded easily into any shape?
Answer: A — Aluminium
Q10. Match the uses of metals and non-metals given in Column I with the jumbled names of metals and non-metals given in Column II.
| Column I | Column II |
|---|---|
| (i) Used in electrical wiring | (a) E N X Y G O |
| (ii) Most malleable and ductile | (b) N E C O H I R L |
| (iii) Living organisms cannot survive without it. | (c) P E P O R C |
| (iv) Plants grow healthy when fertilisers containing it are added to the soil. | (d) T E N G O I N R |
| (v) Used in water purification | (e) O G D L |
Unscrambled words: (a) OXYGEN (b) CHLORINE (c) COPPER (d) NITROGEN (e) GOLD
(i) → (c) COPPER
(ii) → (e) GOLD
(iii) → (a) OXYGEN
(iv) → (d) NITROGEN
(v) → (b) CHLORINE
Q11. The apparatus shown contains an iron nail suspended inside a closed bottle. Silica gel is placed at the bottom of the bottle. The setup is kept undisturbed for 10 days. What will be observed after 10 days?
Answer: C — The iron nail does not rust because moisture is absent (Silica gel absorbs any moisture present, keeping the air inside the bottle dry. Since rusting needs both air and moisture together, the nail stays rust-free.)
Q12. You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?
The iron nail dipped in oil will not rust. This is because the layer of oil coats the nail completely and prevents air (oxygen) and moisture from coming into contact with the iron surface. Since rusting needs both air and water together, blocking them with oil stops rusting. The nails in water and vinegar will rust, and the one in vinegar will rust faster because vinegar is acidic and speeds up the rusting process.
Q13. Complete the following flow chart:
Magnesium + Air + Heat → Ash (Magnesium oxide)
↓ Water
Magnesium hydroxide solution
↓
Add blue and red litmus solutions separately
↓ ↓
Change in blue litmus solution Change in red litmus solution
↓ ↓
No change (stays blue) Blue
Q14. How do the different properties of metals and non-metals determine their uses in everyday life?
Metals are hard, lustrous, malleable, ductile, sonorous, and good conductors of heat and electricity. Because of these properties, metals like copper and aluminium are used for making electrical wires, iron and copper are used for cooking vessels, and gold and silver are used for making jewellery. Non-metals are usually dull, brittle, and poor conductors of heat and electricity, but they are still very useful — oxygen is needed for breathing, nitrogen is used in fertilisers for plant growth, chlorine is used to purify water, and iodine is used as an antiseptic. So, each material is used for a purpose that matches its own special properties.
Q15. State with reason(s) whether the following statements are True [T] or False [F].
(i) Aluminium and copper are examples of non-metals used for making utensils and statues. [ F ]
Reason: Aluminium and copper are metals, not non-metals. They are lustrous, malleable and good conductors of heat, which is why they are used for utensils and statues.
(ii) Metals form oxides when combined with oxygen, the solution of which turns blue litmus paper to red. [ F ]
Reason: Metal oxides are basic in nature; their solutions turn red litmus paper blue, not blue litmus paper red.
(iii) Oxygen is a non-metal essential for respiration. [ T ]
Reason: Oxygen is a non-metal, and all living organisms need it to breathe and survive.
(iv) Copper vessels are used for boiling water because they are good conductors of electricity. [ F ]
Reason: Copper vessels are used for boiling water because copper is a good conductor of heat, not because of electrical conductivity.
Q16. You are provided with the following materials: Iron, copper, sulphur, coal, plastic, wood, cardboard. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why?
Copper (or iron) would be the best choice for making a pan to boil water. This is because copper and iron are metals that are good conductors of heat, so they heat up quickly and transfer heat efficiently to the water. They are also strong, hard, and can withstand high temperatures. Sulphur and coal are brittle and not suitable for making vessels, while plastic, wood and cardboard are poor conductors of heat and can even burn or melt, so they cannot be used to boil water.
Q17. One of the methods of protecting iron from rust is to put a thin coating of zinc metal over it. Since sulphur does not react with water, can it be used for this purpose? Justify your answer.
No, sulphur cannot be used for this purpose. Although sulphur does not react with water, it is brittle, dull, and not malleable, so it cannot be beaten or coated evenly onto the surface of iron like zinc metal can. Zinc, being malleable, forms a smooth, tightly-sticking protective layer over iron that keeps out both air and moisture. Sulphur would crack, flake off, and fail to give a proper protective coating, so it is not suitable for preventing rusting.
🔑 Key Words (Page 146)
Malleability | Ductility | Lustrous | Sonority | Conduction | Rusting | Corrosion
📌 In a Nutshell (Page 146–148)
- Metals and non-metals are differentiated based on their properties.
- Generally, metals are lustrous, whereas most non-metals are non-lustrous.
- Metals are generally malleable and ductile, while non-metals do not have these properties.
- Metals are good conductors of heat and electricity, but non-metals are generally poor conductors.
- Metals react with oxygen to produce metal oxides which are basic in nature.
- Non-metals react with oxygen to produce oxides which are acidic in nature.
- Generally, non-metals do not react with water.
- Metal objects get damaged when exposed to moist air, and the process is known as corrosion.
- Metals and non-metals have wide applications in everyday life.
