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ICSE Class 7 Chemistry Question 13 of 16

Metals and Non-metals — Question 13

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Question 13

Give a reason why oiling or greasing is done on the exposed moving iron parts of machinery and not preferred on heavy stationary iron parts.

Answer

Oiling or greasing is done on the exposed moving iron parts of machinery as it forms a coating which protects it from rusting. It smoothens the surface and reduces friction in the machinery which is its added advantage.

Being stationary, for heavy iron parts, red lead oxide paint is used as there is no use of reducing the friction.

ICSE Class VII Chemistry Chapter 5 14 Marks

Metals and Non-Metals — Quick Study Guide

Elements are broadly classified as metals, non-metals, or metalloids based on their physical and chemical properties.

Key Properties

  • Metals: Lustrous, malleable, ductile, sonorous, good conductors, high density
  • Non-metals: Dull, brittle, poor conductors, non-sonorous, low density
  • Metalloids: Properties of both (e.g., Silicon, Germanium)

Chemical Reactions

  • Metal + O2 → Basic oxide (turns red litmus blue)
  • Non-metal + O2 → Acidic oxide (turns blue litmus red)
  • Metal + Acid → Salt + H2

Exam Tips

  • Know all exceptions: Mercury (liquid), Graphite (conducts), Diamond (lustrous), Na/K (soft)
  • Learn the comparison table (8 properties) thoroughly
  • Practice writing equations for metal reactions
  • Know uses of at least 5 metals and 5 non-metals

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