Metals and Non-Metals Class 10 || Science|| Chapter 3 Notes

Metals and Non-Metals Class 10 ||Science|| Chapter 3 Notes

1. Physical Properties of Metals and Non-Metals

a) Physical Properties of Metals

  1. Luster: Metals are shiny, which is why objects like gold and silver are used to make jewelry.

  2. Malleability: Metals can be hammered into thin sheets. Example: Aluminum foils used in packaging.

  3. Ductility: Metals can be drawn into thin wires. Example: Copper wires used in electrical wiring.

  4. Good Conductors of Heat and Electricity: Metals allow heat and electricity to pass through them easily. Example: Iron pans used in cooking and copper in electric circuits.

  5. High Melting and Boiling Points: Metals generally have high melting and boiling points, making them suitable for high-temperature applications.

  6. Sonorous: Metals produce a ringing sound when struck. This is why bells are made from metals like bronze.

b) Physical Properties of Non-Metals

  1. Non-Lustrous: Non-metals do not have a shiny surface, except for iodine which is an exception.

  2. Brittleness: Non-metals are brittle and break easily when hammered, unlike metals. Example: Sulphur and phosphorus.

  3. Poor Conductors of Heat and Electricity: Most non-metals are insulators. Example: Rubber is used in electrical insulations.

  4. Low Melting and Boiling Points: Non-metals usually have lower melting and boiling points compared to metals (except for carbon in the form of diamond, which has a very high melting point).

  5. Non-Sonorous: Non-metals do not produce a ringing sound when struck.

2. Chemical Properties of Metals and Non-Metals

a) Reaction of Metals

  1. Reaction with Oxygen:

    • Metals react with oxygen to form metal oxides, which are generally basic in nature.

    • Example:

      4Na+O2→2Na2O
      • Sodium reacts with oxygen to form sodium oxide.

      Some metal oxides dissolve in water to form alkalies (like sodium hydroxide or potassium hydroxide).

      Na2O+H2O→2NaOH

  2. Reaction with Water:

    • Some metals react with water to produce metal hydroxides and hydrogen gas.

    • Example:

      2Na+2H2O→2NaOH+H2
      • Sodium reacts with water to form sodium hydroxide and hydrogen gas.

      Metals like potassium and sodium react vigorously with water, while others like iron react slowly.

  3. Reaction with Acids:

    • Metals react with acids to produce salt and hydrogen gas.
    • Example:Zn+2HCl→ZnCl2+H2
      • Zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas.

  4. Reaction with Other Metal Salts (Displacement Reactions):

    • More reactive metals displace less reactive metals from their compounds.
    • Example:CuSO4+Fe→FeSO4+Cu
      • Iron displaces copper from copper sulfate solution, forming iron sulfate and copper.

b) Reaction of Non-Metals

  1. Reaction with Oxygen:

    • Non-metals react with oxygen to form non-metal oxides, which are acidic in nature.
    • Example:C+O2→CO2
      • Carbon reacts with oxygen to form carbon dioxide, which is an acidic oxide.

  2. Reaction with Water:

    • Non-metals do not react with water in the same way metals do. For example, phosphorus reacts with oxygen, but not with water.

  3. Reaction with Acids and Bases:

    • Non-metals generally do not react with acids, but they may react with bases to form salts.
    • Example:Cl2+NaOH→NaCl+NaOCl+H2O
      • Chlorine reacts with sodium hydroxide to form sodium chloride and sodium hypochlorite.

3. The Reactivity Series

  • The Reactivity Series of metals is a list of metals arranged in the order of their decreasing reactivity.
  • Highly reactive metals (like potassium and sodium) are at the top, while less reactive metals (like gold and platinum) are at the bottom.
  • This helps in predicting how metals will react with acids, water, or other substances.

4. Occurrence of Metals: Ores and Extraction

a) Ores

  • Ores are minerals from which metals can be extracted profitably. Metals are usually found in the earth’s crust in the form of ores.
    • Example: Bauxite (Al₂O₃.2H₂O) is the ore of aluminum, and Hematite (Fe₂O₃) is the ore of iron.

b) Extraction of Metals

  • The process of extraction depends on the reactivity of the metal.
    1. Metals low in the reactivity series (like copper, silver, gold) are obtained by reducing their oxides with heat alone.2HgO→heat2Hg+O2
    2. Metals in the middle of the reactivity series (like iron, zinc) are extracted by heating their ores with carbon.ZnO+C→heatZn+CO
    3. Metals high in the reactivity series (like sodium, potassium) are extracted by electrolysis of their molten salts.

5. Corrosion of Metals

  • Corrosion is the process in which metals are gradually destroyed by reacting with substances like water and oxygen.

  • The most common example is the rusting of iron.

    • Rusting occurs when iron reacts with oxygen and water to form iron oxide.4Fe+3O2+2H2O→2Fe2O3

    Prevention of Corrosion:

    • Painting: Prevents air and moisture from coming in contact with the metal.
    • Galvanization: Coating iron with a layer of zinc to prevent rusting.
    • Alloying: Mixing metals with other elements to improve resistance to corrosion. Example: Stainless steel (an alloy of iron, carbon, and chromium) does not rust easily.

6. Alloys

  • An alloy is a homogeneous mixture of a metal with other metals or non-metals.

  • Alloying improves the properties of metals, such as increasing their strength or resistance to corrosion.

    Examples:

    • Brass: Alloy of copper and zinc.
    • Bronze: Alloy of copper and tin.
    • Stainless Steel: Alloy of iron, carbon, and chromium, used for making utensils and surgical instruments because it does not rust.

7. Uses of Metals and Non-Metals

a) Uses of Metals

  • Iron: Used in construction (buildings, bridges) and making machines and vehicles.
  • Copper: Used in electrical wiring due to its excellent conductivity.
  • Aluminum: Used in making aircraft bodies, packaging foils, and kitchen utensils due to its lightweight and non-corrosive nature.
  • Gold and Silver: Used for making jewelry and coins due to their luster and rarity.

b) Uses of Non-Metals

  • Oxygen: Essential for respiration and combustion.
  • Nitrogen: Used in fertilizers to promote plant growth.
  • Carbon: Used in the form of graphite for making electrodes and as diamond for cutting tools.
  • Chlorine: Used in water purification and the production of PVC (polyvinyl chloride).

8. Summary

Metals and non-metals have distinct physical and chemical properties, making them useful in different applications. Metals are generally hard, shiny, and good conductors of heat and electricity, while non-metals are brittle, non-conductors, and used in various chemical processes. Understanding their properties helps us harness them effectively for industrial, medical, and domestic purposes.