Class 7 Science

Chapter 4 Solutions — The World of Metals and Non-metals

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Solutions

Overview

Step-by-step NCERT solutions for The World of Metals and Non-metals (Chapter 4, NCERT Class 7 Science) — every question and answer worked out in full, not just the final result. You can also read the The World of Metals and Non-metals textbook chapter.

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All 12 questions in The World of Metals and Non-metals are solved in the PDF. Here's what's inside, exercise by exercise:

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1.
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?
- (i) Aluminium
- (ii) Copper
- (iii) Iron
- (iv) Gold
2.
Which of the following metal catches fire when it comes in contact with water?
- (i) Copper
- (ii) Aluminium
- (iii) Zinc
- (iv) Sodium
3.
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.
- (ii) Metals form oxides when combined with oxygen, the solution of which turns blue litmus paper to red.
- (iii) Oxygen is a non-metal essential for respiration.
- (iv) Copper vessels are used for boiling water because they are…
Why are only a few metals suitable for making jewellery?
5.
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:
- (i) Used in electrical wiring
- (ii) Most malleable and ductile
- (iii) Living organisms cannot survive without it.
- (iv) Plants grow healthy when fertilisers containing it are added to the soil.
- (v) Used in water purification Column II:
- (a) E N X Y G O
- (b) N E C O H…
What happens when oxygen reacts with magnesium and sulfur. What are the main differences in the nature of products formed?
Complete the following flow chart: [A substance] + Air → Heat → Ash → Water → Add blue and red litmus solutions separately → Change in blue litmus solution: [?] → Change in red litmus solution: Blue → [Nature: ?]
You are provided with the following materials. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why? iron, copper, sulfur, coal, plastic, wood, cardboard
You are provided with three iron nails, each dipped in oil, water and vinegar. Which iron nail will not rust, and why?
How do the different properties of metals and non-metals determine their uses in everyday life?
One of the methods of protecting iron from getting rusted is to put a thin coating of zinc metal over it. Since sulfur does not react with water, can it be used for this purpose? Justify your answer.
An ironsmith heats iron before making tools. Why is heating necessary in this process?

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Worked examples

2 questions from The World of Metals and Non-metals, solved step by step.

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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? (i) Aluminium (ii) Copper (iii) Iron (iv) Gold

The question asks which metal is used for food packaging because it is cheap and can be beaten into thin, flexible sheets.

Evaluating each option:

(i) Aluminium — Correct. Aluminium is inexpensive, highly malleable (it can be beaten into very thin foil), lightweight, and does not react with food. Aluminium foil is widely used to wrap food items such as sandwiches, chocolates, and takeaway containers.

(ii) Copper — Incorrect. Copper is more expensive than aluminium and is not commonly used for food packaging.

(iii) Iron — Incorrect. Iron reacts with moisture to form rust, making it unsuitable for direct food packaging; it is also heavier.

(iv) Gold — Incorrect. Gold is far too expensive to use for everyday food packaging, even though it is highly malleable.

The chapter states that aluminium foil is used for wrapping food items as a practical example of malleability.

Answer: (i) Aluminium — it is cheap, highly malleable, and its thin sheets can be folded easily into any shape for food packaging.

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Which of the following metal catches fire when it comes in contact with water? (i) Copper (ii) Aluminium (iii) Zinc (iv) Sodium

The question asks which metal reacts so vigorously with water that it catches fire.

Evaluating each option:

(i) Copper — Incorrect. Copper does not react with water under ordinary conditions.

(ii) Aluminium — Incorrect. Aluminium has a protective oxide layer that prevents it from reacting with water under normal conditions.

(iii) Zinc — Incorrect. Zinc reacts with steam at high temperatures but does not catch fire on contact with water.

(iv) Sodium — Correct. The chapter states that sodium is stored in kerosene because it reacts vigorously with oxygen and water, generating a lot of heat. When sodium contacts water, it reacts so rapidly that the heat produced is enough to ignite the hydrogen gas released, causing fire.

The chapter explicitly mentions: 'sodium is a metal which is stored in kerosene because it reacts vigorously with oxygen and water.'

Answer: (iv) Sodium — it reacts vigorously with water, releasing large amounts of heat that can cause it to catch fire; it is therefore stored in kerosene.

All 12 questions in The World of Metals and Non-metals are solved step by step in the Solutions PDF above.

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Chapter 4 Solutions — The World of Metals and Non-metals

Overview

What these solutions cover

Let Us Enhance Our Learning

Worked examples

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? (i) Aluminium (ii) Copper (iii) Iron (iv) Gold

Which of the following metal catches fire when it comes in contact with water? (i) Copper (ii) Aluminium (iii) Zinc (iv) Sodium

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