NCERT Solutions for Class 7 Science Chapter 4 The World of Metals and Non-metals

Have you ever thought about the coins in your pocket, the spoon you eat with, and even the jewelry your family treasures? All these are made of metals. On the other hand, things like the graphite inside your pencil, the wooden or plastic handle of a broom, or the oxygen you breathe are non-metals. These two categories of materials - metals and non-metals play an important role in our daily lives. In this article, we will learn the difference between them, and also the physical and chemical properties of metals and non-metals, along with their characteristics, such as the conductivity of metals and non-metals, the reactivity of metals and non-metals with water, air, etc.

NCERT Solutions for Class 7 Science will offer a systematic and structured approach for the exercise problems in the NCERT to prepare well for your exams by providing detailed solutions to all the exercise questions given in the book. Our subject matter expert prepares these NCERT solutions, which also serve as a valuable resource for students to enhance their exam performance.

NCERT Solutions for Class 7 Science Chapter 4: Download PDF

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NCERT Solutions for Class 7 Science Chapter 4 (Exercise Questions with Answers)

Question 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

Answer:

Aluminium foil is commonly used to make food packaging materials. Due to its malleability, it can be beaten into thin sheets.

Hence, the correct answer is option (i).

Question 2: Which of the following metals catches fire when it comes in contact with water?

(i) Copper

(ii) Aluminium

(iii) Zinc

(iv) Sodium

Answer:

The reactivity of Sodium with water is very high; therefore, it generates heat when it comes into contact with water. To prevent this, it is stored in kerosene.

Hence, the correct answer is option (iv).

Question 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

red. [ ]

(iii) Oxygen is a non-metal essential for respiration. [ ]

(iv) Copper vessels are used for boiling water because they are good conductors of electricity. [ ]

Answer:

(i) [F] False, Aluminium and copper are known as metals, for their properties like Malleability,

lustre, and hardness.

(ii) [F] False, Metal oxides are generally basic in nature, as we know basic solutions turn red litmus paper into blue.

(iii) [T] True, Oxygen is a non-metal essential for respiration. When we breathe, we inhale oxygen and exhale carbon dioxide.

(iv) [F] False, Copper vessels are used for boiling water because they are good conductors of heat.

Question 4: Why are only a few metals suitable for making jewellery?

Answer:

Metals are Suitable for jewellery making due to these specific properties:

• Malleability & Ductility: Easily shaped and drawn into wires

• Lustre: Has a shiny appearance

• Resistance to Corrosion: doesn’t tarnish easily

• High Value or Rarity: Metals like silver and gold possess these qualities well.

Question 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.

Answer:

Question 6: What happens when oxygen reacts with magnesium and sulfur? What are the main differences in the nature of the products formed?

Answer:

When oxygen reacts with magnesium (a metal), it forms magnesium oxide. When oxygen reacts with sulfur (a non-metal), it forms sulfur dioxide gas. Main Difference: Magnesium oxide forms a basic solution in water. Sulfur dioxide forms an acidic solution in water. As we know, generally, metal oxides are basic, and non-metal oxides are acidic.

Question 7: Complete the following flow chart:

Answer:

Question 8: 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?

Answer:

To make pans for boiling water, we need to transfer heat efficiently. As we know, metals (Iron, Copper) are good conductors of heat. Materials like sulfur, coal, plastic, wood, and cardboard are poor conductors of heat, so these are unsuitable for cooking vessels. Therefore, the best choice would be copper or iron.

Question 9: You are provided with three iron nails, each dipped in oil, water, and vinegar. Which iron nail will not rust, and why?

Answer:

As we know, rusting requires both air (oxygen) and water. Oil prevents the iron surface from contacting air and moisture, which inhibits rust. Therefore, the iron nail dipped in oil will not rust or rust much slower than the others.

Question 10: How do the different properties of metals and non-metals determine their uses in everyday life?

Answer:

The different properties of metals and non-metals determine their uses in everyday:

Metals: Good Conductor of electricity ( used in electric wires), Good Conductor of heat ( used in making cookware), Malleability/Ductility (used in making sheets, wires, and jewellery), Highly Lustrous (decoration), etc.

Non-metals: Poor conductors of heat (insulation, handles), Chemical Properties (Chlorine for purification, Iodine as antiseptic, etc.), Gaseous State (Nitrogen for fertilizers and Oxygen for breathing), etc.

Question 11: One of the methods of protecting iron from rusting 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.

Answer:

Sulfur is brittle in nature and does not form a durable protective layer like zinc does in galvanization. That’s why sulfur coating can be easily cracked. Therefore, we can not use sulfur for this purpose.

Question 12: An ironsmith heats iron before making tools. Why is heating necessary in this process?

Answer:

Heating the iron makes it more malleable and softer. This allows the ironsmith to beat the hot iron and shape it into desirable forms relatively easily.

Approach to Solve Questions of Class 7 Science Chapter 4

To solve questions from the chapter The World of Metals and Non-Metals:

• Focus on understanding the characteristics of metals and non-metals.
• Understand their physical and chemical properties of metals and non-metals, such as Malleability, Ductility, Sonority, Conduction of heat, and Conduction of electricity.
• Try to learn and memorize key concepts of the chapter, such as the effect of air and water on metals and non-metals.
• Use some common tricks, such as paying attention to key differences between metals and non-metals.
• Make suitable short notes for quick revision.
• Revise notes timely.
• Practice previous year question papers of the exam, as well as practice mock tests accordingly.

Topics and Sub-topics Covered in the NCERT Textbook

4.1 Properties of materials:

4.1.1 Malleability

4.1.2 Ductility

4.1.3 Sonority

4.1.4 Conduction of heat

4.1.5 Conduction of electricity

4.2 Effect of air and water on metal: Iron

4.2 Effect of air and water on other metals

4.4 Substances that behave differently from metals in air and water

4.6 Are non-metals essential in everyday life?

Practice Questions for Class 7 Science Chapter 4

Question 1: Which of the following catches fire when it comes in contact with water?

1. Sodium

2. Copper

3. Gold

4. Aluminium

Answer:

The reactivity of Sodium with water is very high, therefore, it generates heat when it comes into contact with water. To prevent this, it is stored in kerosene.

Hence, the correct answer is option (A)

Question 2: Why are only a few metals suitable for making jewellery?

Answer:

Metals are Suitable for jewellery making due to these specific properties:

• Malleability & Ductility: Easily shaped and drawn into wires

• Lustre: Has a shiny appearance

• Resistance to Corrosion: doesn’t tarnish easily

• High Value or Rarity: Metals like silver and gold possess these qualities well.

Question 3: What happens when oxygen reacts with magnesium and sulfur? What are the main differences in the nature of the products formed?

Answer:

When oxygen reacts with magnesium (a metal), it forms magnesium oxide. When oxygen reacts with sulfur (a non-metal), it forms sulfur dioxide gas. Main Difference: Magnesium oxide forms a basic solution in water. Sulfur dioxide forms an acidic solution in water. As we know, generally, metal oxides are basic, and non-metal oxides are acidic.

Question 4. What is the effect of air and water on iron metal?

Answer: We know that Iron is a reactive metal, and when it comes into contact with air (oxygen) and water (moisture), it follows a redox reaction that leads to corrosion, commonly known as rusting.

Rusting reaction:

4Fe+3O₂+6H₂O→4Fe(OH)₃

Fe(OH)₃→Fe₂O₃.xH₂O(rust)

NCERT Solutions for Class 7 Science Chapter-wise

The chapter-wise solutions are given below:

NCERT Books and NCERT Syllabus

The NCERT books and syllabus links for class 7 are given below:

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