NCERT Revision Notes for Chapter 3 Metals and Non-metals Class 10 Science
CBSE NCERT Revision Notes1
Answer
→ Elements can be classified as metals and non-metals on the basis of their properties.
• Examples of some metals are: Iron (Fe), Aluminium (Al), Silver (Ag), Copper (Cu).
• Examples of some non-metals are: Hydrogen (H), Nitrogen (N), Sulphur (S), Oxygen (O).
2
Answer
|
Property |
Metals |
Non-Metals |
|
1. Lustre |
Metals have shining surface. |
They do not have shining surface. • Except Iodine. |
|
2. Hardness
|
They are generally hard. • Except Sodium, Lithium and Potassium which are soft and can be cut with knife. |
Generally soft. • Except Diamond, a form of carbon which is the hardest natural substance. |
|
3. State |
Exist as solids. • Except Mercury. |
Exist as solids or gaseous. • Except Bromine. |
|
4. Malleability |
Metals can be beaten into thin sheets. • Gold and Silver are the most malleable metals. |
Non-metals are non-malleable. |
|
5. Ductility |
Metals can be drawn into thin wires. |
They are non-ductile. |
|
6. Conductor of heat & electricity |
Metals are good conductors of heat and electricity. • Silver (Ag) and Copper (Cu): Best conductors of heat. • Lead (Pb), Mercury (Hg) poor conductor of heat. |
Non-metals are poor conductor of heat and electricity. • Except Graphite. |
|
7. Density |
Generally have high density and high melting point. • Except Sodium and Potassium. |
Have low density and low melting point. |
|
8. Sonorous |
Metals produce a sound on striking a hard surface. |
They are not sonorous. |
|
9. Oxides |
Metallic oxides are basic in nature. |
Non-metallic oxides are acidic in nature. |
3
Answer
• Reaction of metals with air
→ Metals combine with oxygen to form metal oxide.
Metal + O2 → Metal oxide
Examples:
(i) 2Cu + O2 → 2CuO [Copper oxide (black)]
(ii) 4Al + 3O2 → 2Al2O3 [Aluminium oxide]
(iii) 2Mg + O2 → 2MgO
The reactivity of different metals are different with O2.
→ Na and K react so vigorously that they catch fire if kept in open so they are kept immersed in kerosene.
→ Surfaces of Mg, Al, Zn, Pb are covered with a thin layer of oxide which prevent them from further oxidation.
→ Fe does not burn on heating but iron fillings burn vigorously.
→ Cu does not burn but is coated with black copper oxide.
→ Au and Ag does not react with oxygen.
→ Amphoteric Oxides: Metal oxides which react with both acids as well as bases to produce salts and water are called amphoteric oxides.
Examples:
(i) Al2O3 + 6HCl → 2AlCl3 + H2O
(ii) Al2O3 + 2NaOH → 2NaAlO2 + H2O (Sodium Aluminate)
• Reaction of metals with water
→ Metal + Water → Metal oxide + Hydrogen
→ Metal oxide + Water → Metal hydroxide
Examples:
(i) 2Na + 2H2O → 2NaOH + H2 + Heat
(ii) Ca + 2H2O → Ca(OH)2 + H2
(iii) Mg + 2H2O → Mg(OH)2 + H2
(iv) 2Al + 3H2O → Al2O3 + 3H2
(v) 3Fe + 4H2O → Fe3O4 + 4H2
• Reaction of metals with acids (Dilute)
→ Metal + Dilute acid → Salt + H2
→ Cu, Ag, Hg do not react with dil. acids.
Examples:
(i) Fe + 2HCl → FeCl2 + H2
(ii) Mg + 2HCl → MgCl2+ H2
(iii) Zn + 2HCl → ZnCl2 + H2
(iv) 2Al + 6HCl → 2AlCl3 + 3H2
• Reaction of Metals with Solutions of other Metal Salts
→ Metal A + Salt solution B → Salt solution A + Metal B
→ Reactive metals can displace less reactive metals from their compounds in solution form.
Fe + CuSO4→ FeSO4 + Cu
4
Answer
The reactivity series is a list of metals arranged in the order of their decreasing activities.
• Reaction of Metals with Non-metals
→ Reactivity of elements is the tendency to attain a completely filled valence shell.
→ Atoms of the metals lose electrons from their valence shell to form cation. Atom of the non-metals gain electrons in the valence shell to form anion.
E.g.: Formation of NaCl
Na → Na+ + e-
2, 8, 1→ 2, 8
Sodium cation
Cl + e- → Cl-
2, 8, 7 → 2, 8, 8
Chloride anion
5
Answer
The compounds formed by the transfer of electrons from a metal to a non-metal are called ionic compounds or electrovalent compounds.
• Properties of Ionic Compounds
(i) Physical nature: They are solid and hard, generally brittle.
(ii) Melting and Boiling Point: They have high melting and boiling point.
(iii) Solubility : Generally soluble in water and insoluble in solvents such as kerosene, petrol etc.
(iv) Conduction of electricity : Ionic compounds conduct electricity in molten and solution form but not in solid state.
• Occurrence of Metals
(i) Minerals: The elements or compounds which occur naturally in the earth’s crust are called minerals.
(ii) Ores: Minerals that contain very high percentage of particular metal and the metal can be profitably extracted from it, such minerals are called ores.
6
Answer
Step 1. Enrichment of ores.
Step 2. Extraction of metals.
Step 3. Refining of metals. 
7
Answer
Gangue → Roasting → Calcination → Reduction
• Important terms
(a) Gangue : Ores are usually contaminated with large amount of impurities such as soil, sand etc. called gangue.
(b) Roasting : The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is called roasting.
2ZnS + 3O2 →(Heast) 2ZnO + 2SO2
(c) Calcination : The carbonate ores are changed into oxides by heating strongly in limited air. This process is called calcination.
ZnCO3 →(Heat) ZnO + CO2
(d) Reduction : Metal oxides are reduced to corresponding metals by using reducing agent like carbon.
ZnO + C → Zn + CO
• Refining of metals: The most widely used method for refining impure metal is electrolytic refining.
(i) Anode : Impure copper
(ii) Cathode : Strip of pure copper
(iii) Electrolyte : Solution of acidified copper sulphate
→ On passing the current through electrolyte, the impure metal from anode dissolves into the electrolyte.
→ An equivalent amount of pure metal from the electrolyte is deposited at the cathode.
→ The insoluble impurities settle down at the bottom of the anode and is called anode mud.
8
Answer
The surface of some metals get corroded when they are exposed to moist air for a long period of time. This is called corrosion.
Examples:
(i) Silver becomes black when exposed to air as it reacts with air to form a coating of silver sulphide.
(ii) Copper reacts with moist carbon dioxide in the air and gains a green coat of copper carbonate.
(iii) Iron when exposed to moist air acquires a coating of a brown flaky substance called rust.
• Prevention of Corrosion
→The rusting of iron can be prevented by painting, oiling, greasing, galvanizing, chrome plating, anodizing or making alloys.
→ Galvanization: It is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
→ Alloy: An alloy is a homogeneous mixture of two or more metals or a metal and a non- metal.
→ Examples of alloy:
(i) Iron: Mixed with small amount of carbon becomes hard and strong.
(ii) Steel: Iron + Nickel and chromium
(iii) Brass: Copper + Zinc
(iv) Bronze: Copper + Tin (Sn)
(v) Solder: Lead + tin
(vi) Amalgam: If one of the metal is mercury (Hg).