Introduction
This chapter explores the
physical and chemical properties of metals and non-metals, their reactivity,
and their uses. It also covers the extraction of metals and the concept of
alloys.
1. Physical Properties of
Metals
Lustre: Metals have a shiny appearance known as
metallic lustre.
Malleability: Metals can be hammered into thin sheets,
making them malleable. Ductility: Metals
can be drawn into wires, demonstrating their ductility. Conductivity: Metals are good conductors of heat and
electricity.
Hardness: Most metals are hard, but some like
sodium and potassium are soft and can be cut with a knife.
Density and Melting Points:
Metals generally have high density and melting points, except for a few
like mercury which is liquid at room temperature.
2. Physical Properties of
Non-Metals
Lack of Lustre: Non-metals
are usually dull in appearance, though iodine is an exception. Brittleness: Non-metals are brittle and cannot be drawn
into wires or hammered into sheets. Poor Conductivity: Non-metals are poor conductors of heat and electricity, with
graphite
being an exception.
Low Density and Melting Points: Non-metals typically have low density and
melting points.
3. Chemical Properties of
Metals
Reaction with Oxygen: Metals react with oxygen to form metal
oxides. For example, 4Na + O₂
→ 2Na₂O (sodium oxide).
Metal oxides are generally basic in nature, but some
like aluminium oxide are amphoteric.
Reaction with Water: Metals
react with water to produce metal hydroxides and hydrogen gas. For example, 2Na
+ 2H₂O → 2NaOH + H₂↑.
Reaction with Acids: Metals
react with acids to produce salt and hydrogen gas. For example, Zn + 2HCl →
ZnCl₂ + H₂↑.
Reaction with Bases: Some
metals react with bases to form complex salts. For example, Al + NaOH →
Na[Al(OH)₄].
4. Chemical Properties of
Non-Metals
Reaction with Oxygen: Non-metals react with oxygen to form
non-metallic oxides, which are acidic in nature. For example, C + O₂ → CO₂.
Reaction with Water: Non-metals
do not usually react with water.
Reaction with Acids and Bases: Non-metals
generally do not react with acids or bases.
5. Displacement Reactions
More reactive metals can displace less reactive
metals from their compounds in solution. For example, Zn + CuSO₄ → ZnSO₄ + Cu.
The reactivity series helps predict which metals will
displace others.
6. Extraction of Metals
Occurrence of Metals:
Metals occur in the earth’s crust in the form of ores.
Steps of Extraction:
Concentration of Ore: Removal of impurities from the ore.
Reduction to Metal: Extracting the metal from its ore,
typically through heating or chemical reduction.
Refining: Purification
of the extracted metal.
Electrolytic Refining:
A process used for refining metals, where the impure metal is made the
anode, and a pure metal strip is made the cathode.
7. Corrosion
Definition: The
gradual deterioration of metals due to the chemical reaction with their
environment. For example, rusting of iron.
Prevention:
Methods include painting, galvanization, and alloying.
8. Alloys
Definition: An
alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
Examples: Brass
(copper + zinc), Bronze (copper + tin), and Steel
(iron + carbon).
Properties of Alloys: Alloys are designed to have properties
superior to the constituent elements, such as increased strength, resistance to
corrosion, or better electrical conductivity.
9. Uses of
Metals and Non-Metals
Metals: Used
in construction, manufacturing, electrical wiring, and utensils.
Non-metals: Used
in fertilizers, water purification, and as insulators.
10. Summary
Metals are generally shiny, malleable, ductile, and
good conductors of heat and electricity, while non-metals are usually dull,
brittle, and poor conductors.
Metals react with oxygen, water, acids, and bases to
form various compounds, while non-metals react mainly with oxygen.
The extraction of metals involves concentration,
reduction, and refining.
Corrosion is a common issue
with metals, which can be prevented through various methods. Alloys are
mixtures of metals designed to enhance specific properties.
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