NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

(i) Is a liquid at room temperature: Mercury (Hg)

(ii) Can be easily cut with a knife: Sodium (Na) / Potassium (K)

(iii) Is the best conductor of heat: Silver (Ag) / Copper (Cu)

(iv) Is a poor conductor of heat: Lead (Pb) / Mercury (Hg)

Malleable: The property of metals that allows them to be beaten or hammered into thin sheets without breaking. Example: Gold and Aluminium.

Ductile: The property of metals that allows them to be drawn or stretched into thin wires. Example: Gold and Copper.

Answer: Sodium is a highly reactive alkali metal that reacts vigorously with oxygen and moisture present in air, generating extreme heat and potentially catching fire. To prevent accidental fires and unwanted oxidation, it is stored submerged in kerosene oil.

(i) Iron with steam:
3Fe (s) + 4H₂O (g) → Fe₃O₄ (s) + 4H₂ (g)

(ii) Calcium with water:
Ca (s) + 2H₂O (l) → Ca(OH)₂ (aq) + H₂ (g)

Answer: Metal oxides that react with both acidic and basic substances to produce salt and water are known as amphoteric oxides.
Examples: Aluminium oxide (Al₂O₃) and Zinc oxide (ZnO).

Reaction with Acid: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Reaction with Base: Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

(i) Mineral: Naturally occurring elements or chemical compounds found in the Earth's crust.

(ii) Ore: Minerals from which a specific metal can be extracted conveniently and profitably.

(iii) Gangue: Unwanted impurities such as soil, sand, and rocky matter associated with extracted ores.

(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and silver metal
(d) AgNO₃ solution and copper metal

Correct Answer: (d) AgNO₃ solution and copper metal (Copper is more reactive than silver and displaces silver from its solution).

(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of the above

Correct Answer: (c) Applying a coating of zinc (Galvanisation is suitable for food-contact cooking containers where paint or grease is non-viable).

Answer:

1. Physical Nature: Ionic compounds are hard, brittle solids due to strong electrostatic attraction between oppositely charged ions.

2. High Melting & Boiling Points: A high amount of heat energy is required to break the strong ionic bonds.

3. Solubility: Generally soluble in polar solvents like water, but insoluble in non-polar solvents like kerosene or petrol.

4. Electrical Conductivity: Conduct electricity in molten state or aqueous solution due to mobile ions, but do not conduct in the solid state.

Answer: Copper does not react with water or steam at any temperature, whereas iron reacts with steam to form iron oxide, causing structural corrosion and rusting over time. Furthermore, copper is a significantly better conductor of heat than steel.