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Materials used in pencils: The writing core of ordinary pencils is made of which substance? Consider the soft, electrically conductive carbon form used for marking on paper. Choose the correct material.

Difficulty: Easy

Graphite
Silicon
Charcoal
Phosphorus

Correct Answer: Graphite

Explanation:

What is being asked?
The material that forms the pencil 'lead'.

Given data

Pencils use a carbon form mixed with clay (no metallic lead).

Concept/Approach
The pencil core is graphite (sp² carbon) blended with clay and waxes; charcoal is too friable, silicon and phosphorus are not used.

Final Answer
Graphite

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