NOTES Chapter 3: Metals and Non-Metals Class 10 Science – CBSE NCERT

 Chapter 3: Metals and Non-Metals

Class 10 Science – CBSE NCERT

In this chapter, students are introduced to metals and non-metals, two important classes of elements. The chapter focuses on the differences in their properties, reactions, and uses. It also highlights how these substances interact in chemical reactions, particularly in terms of their ability to form compounds like salts and oxides.

1. Physical Properties of Metals and Non-Metals

The chapter begins by distinguishing the physical properties of metals and non-metals:

Properties of Metals:

• Luster: Metals are shiny and have a metallic luster (e.g., gold, silver).
• Malleability: Metals can be hammered into thin sheets (e.g., aluminum foil).
• Ductility: Metals can be drawn into thin wires (e.g., copper wires).
• Good Conductors of Heat and Electricity: Metals are excellent conductors of both heat and electricity (e.g., copper, silver).
• Hardness: Most metals are hard (e.g., iron), but some are soft (e.g., sodium).
• High Melting and Boiling Points: Metals generally have high melting and boiling points (e.g., iron melts at 1538°C).
• Density: Most metals are dense (e.g., lead, iron), though some like sodium and potassium are less dense.

Properties of Non-Metals:

• Lack of Luster: Non-metals are generally dull (e.g., sulfur, carbon).
• Brittleness: Non-metals are usually brittle and break easily when solid (e.g., carbon).
• Poor Conductors of Heat and Electricity: Non-metals are poor conductors, except for graphite (e.g., sulfur, oxygen).
• Low Melting and Boiling Points: Non-metals tend to have low melting and boiling points (e.g., oxygen, chlorine).
• Low Density: Non-metals are less dense than metals (e.g., hydrogen, oxygen).
• Existence in Different States: Non-metals exist in all three states of matter at room temperature—solids (e.g., sulfur), liquids (e.g., bromine), and gases (e.g., oxygen).

2. Chemical Properties of Metals and Non-Metals

Metals and non-metals differ in their chemical reactivity and the way they form compounds.

Reactions of Metals:

• With Oxygen: Metals generally form metal oxides when they react with oxygen. These oxides are usually basic in nature.

  • Example:
    $2\text{Mg}+{\text{O}}_2\to 2\text{MgO (Magnesium reacts with oxygen to form magnesium oxide.)}$

• With Water: Many metals react with water to produce hydrogen gas and a base (hydroxide). However, some metals like sodium and potassium react vigorously with water.

  • Example:
    $2\text{Na} + 2\text{H}_2\text{O} \rightarrow 2\text{NaOH} + \text{H}_2$ (Sodium reacts with water to form sodium hydroxide and hydrogen gas.)

• With Acids: Metals react with acids to form salts and hydrogen gas.

  • Example:
    $\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2$ (Zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas.)

Reactions of Non-Metals:

• With Oxygen: Non-metals generally form non-metal oxides, which are acidic in nature.

  • Example:
    $\text{C} + \text{O}_2 \rightarrow \text{CO}_2$ (Carbon reacts with oxygen to form carbon dioxide.)

• With Water: Non-metals do not typically react with water to form bases. For example, chlorine reacts with water to form hydrochloric acid and hypochlorous acid, but this reaction is not typical of all non-metals.

• With Acids: Non-metals do not react with acids in the same way metals do. They tend to form acidic oxides when combined with oxygen, which can further react with water to form acidic solutions.

3. Metal Reactivity Series

The reactivity series is a list of metals arranged in order of their decreasing reactivity. The most reactive metals (e.g., sodium, potassium) are placed at the top, and the least reactive (e.g., gold, platinum) are placed at the bottom. This series helps predict the ability of a metal to displace another metal from its compound.

• Most reactive metals: Sodium, potassium, calcium, magnesium
• Less reactive metals: Iron, zinc, copper
• Least reactive metals: Gold, platinum, silver

4. Extraction of Metals

Metals are extracted from their ores through various processes, depending on their reactivity. The chapter explains the different methods of extraction:

• For Highly Reactive Metals: Metals like sodium and potassium are extracted using electrolysis.
• For Moderately Reactive Metals: Metals like zinc and iron are extracted through reduction using carbon.
• For Least Reactive Metals: Metals like gold, platinum, and silver are extracted by panning or distillation as they are found in their pure form in nature.

5. Uses of Metals and Non-Metals

The chapter discusses the wide range of uses for metals and non-metals in daily life and industries:

Uses of Metals:

• Iron: Used in construction and manufacturing (e.g., buildings, bridges, vehicles).
• Copper: Used for electrical wiring due to its excellent conductivity.
• Aluminum: Lightweight metal used in the construction of aircraft, kitchen utensils, and packaging materials.
• Gold: Used in jewelry and as a form of investment.

Uses of Non-Metals:

• Oxygen: Essential for respiration in living organisms and used in medical treatments.
• Nitrogen: Used in the production of fertilizers and as a refrigerant.
• Carbon: Used in the form of graphite for pencils and as a fuel in the form of coal.
• Chlorine: Used in the production of disinfectants and in water purification.

6. Corrosion of Metals

The chapter also covers corrosion, which is the gradual degradation of metals due to chemical reactions, typically with water and oxygen. The most common example is rusting of iron:

• Rusting of Iron:
  $4\text{Fe} + 3\text{O}_2 + 6\text{H}_2\text{O} \rightarrow 4\text{Fe(OH)}_3$ (Iron reacts with oxygen and water to form iron hydroxide, which later turns into rust.)

To prevent corrosion, metals are often coated with paint, oil, or other substances to protect them from air and moisture.

7. Alloys

An alloy is a mixture of two or more metals, or a metal and a non-metal, that is designed to have specific properties. Alloys are generally stronger, harder, or more resistant to corrosion than pure metals. Some common alloys include:

• Steel: An alloy of iron and carbon, used in construction, tools, and machinery.
• Bronze: An alloy of copper and tin, used in coins and statues.
• Brass: An alloy of copper and zinc, used in plumbing and electrical applications.
• Stainless Steel: An alloy of iron, carbon, and chromium, known for its resistance to rust and corrosion.

8. Differences Between Metals and Non-Metals

At the end of the chapter, the key differences between metals and non-metals are summarized:

• Metals are generally hard, lustrous, and good conductors of electricity, while non-metals are brittle, lack luster, and are poor conductors.
• Metals tend to lose electrons during reactions, whereas non-metals gain or share electrons.
• Metals form basic oxides, while non-metals form acidic oxides.

Conclusion

Chapter 3 on Metals and Non-Metals provides a comprehensive understanding of the physical and chemical properties of metals and non-metals, their reactions, uses, and methods of extraction. It also emphasizes the importance of these elements in daily life and industries, as well as their environmental impacts, such as corrosion and the need for protective coatings. Understanding these properties is essential for students to appreciate the role of materials in both nature and technology.