Class 10 Science Chapter-3 Metals And Non Metals

Elements can be classified as metals and non-metals on the basis of their properties.

Physical Properties of metals and non metals

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.

Metalloids can be defined as chemical elements whose physical and chemical properties fall in between the metal and non-metal .

Metal.

Best conductor of heat =silver.

Poor conductor of heat =lead.

Low melting point=gold.

most ductile=gold.

Non lustrous=iron.

metal which react with water on boiling =magnesium.

Does not react with steam=copper

Liquids at room temperature =mercury.

Soft metals or can be easily cut with a knife=sodium.

Most abundant metal=aluminium.

Keep in paraffin wax=lithium.

Heaviest metal=osmium.

Metal do not corrode easily=gold and silver.

Metal kept in kerosene oil =sodium.(because it reacts with air and Water vigorously at room temperature)

Metal user to make Jewellery - these are most ductile, malleable and lustrous metals. These metals have little affinity for oxygen and thus, are not attacked easily by air or moisture.

Aluminum is a highly reactive metal, yet it is used make utensils for cooking because it is good conductor of electricity. Moreover, when exposed to air, its surface gets covered with thin layer of oxides which prevents metal underneath from further corrosion

Metal used to make hot water tanks =copper (because it does not react with Hot water. It is best conductor of heat and electricity also. it has high melting point.

non metal

Lustrous=iodine.

Liquid=bromine.

Chemical Properties of Metals

• Electropositive=metals are electropositive in nature as they from positive ions by loss of electrons.

• 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 + O 2 → 2MgO

Silver and gold do not react with oxygen even at high temperature.

• Reaction of metals with water

→ Metal + Water → Metal oxide + Hydrogen

Examples:

2Na + 2H₂O → 2NaOH + H₂ + Heat

Ca + 2H₂O → Ca(OH)₂ + H₂

2Al + 3H₂O → Al₂O₃ + 3H₂

3Fe + 4H₂O → Fe₃O₄ + 4H₂

3Zn + H₂O → ZnO + H₂

Metal oxides are basic in nature.

Magnesium when react with water slowly form magnesium hydroxide with hydrogen gas.

Mg + 2H₂O → Mg(OH)₂ + H₂

when steam is passed over magnesium form magnesium oxide with hydrogen gas.

Mg + H₂O → MgO + H₂

Amphoteric Oxides:
Metal oxides which react with both acids as well as bases to produce salts and water are called 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

→ Metal oxide + Water → Metal hydroxide

• 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 zinc with dilute nitric acid does not produce hydrogen gas because nitric acid is strong oxidising agent. It oxidised the produced hydrogen to water and itself revised to No,No2,N2O.

# Metal like magenisum and manganese do not react with dil HNO3 to evolve H2 gas.

• 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

# Zn+CuSo₄ → ZnSo₄+Cu.

Cu+ZnSo₄ → no reaction.

Because copper metal is less reactive than zinc metal and hence, cannot displace zinc from its Salt solution.

Reactivity Series

The reactivity series is a list of metals arranged in the order of their decreasing

activities.

Metals used as reducing agents by displacing metals of lower reactivity from their compounds =Na, Ca, Al, Mn.

K (Potassium) > Na (Sodium) > C (Calcium) > Mg (Magnesium) > Al (Aluminium) > Zn (Zinc) > Fe (Iron) > Pb (Lead) > H (Hydrogen) > Cu (Copper) > Hg (Mercury) > Ag (Silver) > Au (Gold)

• 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

Ionic compounds

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 Point: They have high melting point Because ionic compounds have rigid structure. Atoms are strongly bonded with each other. To break up the structure high temperature is required.

(iii) Boiling Point: They have high boiling point.

(iv) Solubility : These are 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

It occurs in Earth’s crust, sea-water.

Minerals

Ores

Gangue

The elements or compounds which occur naturally in the earth’s crust are called minerals.

Minerals that contain very high percentage of particular metal and the metal can be profitably extracted from it, such minerals are called ores. E.g Bouxite ore – Aluminium

Haematite- iron

Gangues the impurities of sand and rockey materials present in the presence is called gangue

Extraction of Metals from Ores

Step 1. Enrichment of ores.
Step 2. Extraction of metals.
Step 3. Refining of metals.

Steps Involved in Extraction of Metals from Ores

Gangue → Roasting → Calcination → Reduction

Roasting

Calcination

1.in this the ore is heating in the present of excess of air.

2. it is done for sulphide ore. 3. So2 gas is evolved..

1. in this the ore is heating in the absence of excess of air.

2. it is done for carbonate ore.

3. Co₂gas is evolved.

2ZnS + 3O₂ →(Heat) 2ZnO + 2SO₂

ZnCO₃→(Heat) ZnO + CO2

Reduction : Metal oxides are reduced to corresponding metals by using reducing agent like carbon.
ZnO + C → Zn + CO

Metal. Ore.

Copper. Copper pyrites

zinc. Zinc blende(ZnS)

lead. Galena(PbS)

aluminum bauxite.

Iron. Haematite(Fe₂O₃)

mercury. Cinnabar(HgS)

copper. Copper glance.

Sodium. Rock salt(NaCl)

Extraction of copper from sulphide ore.

In the extraction of copper from its sulphide ore, the metal is finally obtained by the reduction of cuprous oxide with copper(I) sulphide.
2Cu₂S+3O₂→2Cu₂O+2SO₂
2Cu₂O+Cu₂S→6Cu+SO₂

Sodium can be obtained from sodium chloride by the process of electrolytic reduction.

• 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.

In the electrolytic refining of metal M

anode=crude metal M.

Cathode=thin strip of pure mental M.

Electrolyte=some salt of metal M.

Corrosion

The surface of some metals get corroded when they are exposed to moist air for a long period of time. This is called corrosion.

The process of slowly eating away of metal due to attack of air, water, etc on the surface of metal 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.

• Methods for the Prevention of Corrosion

The rusting of iron can be prevented by painting, oiling and greasing, 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.

Electroplating is also used to prevent corrosion.

The rusting of iron can be prevented by making alloys.

Alloy :

An alloy is a homogeneous mixture of two or more metals or a metal and a non- metal.

properties of alloy.

1.)it has better properties than the metal in its purest form.

2.) the electrical conductivity of an alloy is less than pure.

3.) it has low melting point than its constituents.

4.)it is resistant to corrosion.

Examples of alloy:

(i) Iron : Mixed with small amount of carbon becomes hard and strong. Also when iron mix with nickel and chromium, and does not rust
(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). then alloy is called amalgam. An alloy of lead and tin is used for welding electrical wire together.

Search This Blog