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CBSESecondary School (English Medium) Class 8
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Syllabus

Types of Element: Metals

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Topics

  • Introduction
  • General Properties of Metals
  • Experiment

Introduction

Metals are found in the earth’s crust, usually as metal ores mixed with other elements. They are also present in rocks, water, and atmospheric dust. Metals are strong and durable, used to make automobiles, satellites, cooking utensils, and more. Most metals are hard, but some, like sodium and potassium, are soft enough to be cut with a knife. Mercury is a unique metal that is liquid at room temperature.

Examples of metals are gold, silver, iron, copper, aluminium, magnesium, calcium, sodium, and platinum.

General Properties of Metals

Lustre Metals have a shiny appearance and reflect light.
Hardness Most metals are hard, though some (like sodium and potassium) are soft.
Malleability Metals can be hammered into thin sheets without breaking.
Ductility Metals can be drawn into wires.
High Melting and Boiling Points Metals generally have high melting and boiling points (except for mercury, which is liquid at room temperature).
Good Conductors Metals conduct heat and electricity efficiently.
High Density Metals usually have a high density, making them heavy.
Sonorous Metals produce a ringing sound when struck.
Form Cations Metals lose valence electrons to form positively charged ions (cations).

 

Experiment

1. Aim: To observe the physical properties, such as lustre and malleability, of different objects made from iron, copper, aluminium, and carbon.

2. Requirements: iron nail or sheet, copper wire, aluminium wire, piece of coal, sandpaper, and hammer.

3. Procedure

  • Rub each object (iron, copper, aluminium, and coal) on sandpaper to reveal a fresh surface and observe if it has lustre (shiny appearance) or is pale.
  • Carefully hammer each object with force to see if it is malleable (can be hammered into thin sheets) or brittle (breaks easily).
Object Is the surface shining? Yes/No Does the shape flatten/break into small pieces on hammering?
Iron nail Yes Flattens
Copper wire Yes Flattens
Aluminium wire Yes Flattens
Coal piece No Breaks into small pieces

 

Category Elements
Elements having a shiny surface Iron, Copper, and Aluminium
Elements that flatten on hammering Iron, Copper, and Aluminium
Elements with a dull surface Carbon (Coal piece)
Elements that break on hammering Carbon (Coal piece)

4. Conclusion: The experiment shows that elements have different physical properties

  • Metals like iron, copper, and aluminium have lustre and are malleable. Nonmetals like carbon (coal) are dull and brittle.
  • This experiment demonstrates the basic classification of elements into metals and non-metals based on their physical characteristics. Further details will be explored in the study of metals and nonmetals.
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