In a circuit-testing activity, the bulb glows when Sukhmani places a pencil's 'lead' between the…
In a circuit-testing activity, the bulb glows when Sukhmani places a pencil's 'lead' between the two wires. Sukhmani concludes that pencil lead must be a metal, since it conducts electricity. Lalit says pencil lead is actually graphite, a form of carbon, and carbon is a non-metal — one property alone can't decide it. Who is thinking like a scientist?
Who do you think is right? Pick one.
The answer: Lalit is right, pencil lead is graphite, which is a non-metal
Why
Sukhmani is using a real pattern: most things that conduct electricity well are metals, and most non-metals don't conduct. But a pattern that is usually true is not a rule that is always true, and one test can't settle the question. Despite its name, pencil 'lead' contains no lead metal at all — it is graphite mixed with clay, and graphite is a form of carbon, a non-metal. Graphite is a famous exception: it conducts electricity, yet in other ways it behaves like a non-metal. Check another property and it shows: a copper wire bends, and can be flattened by hammering, but a pencil lead snaps and crumbles — it is brittle, not malleable or ductile. Scientists decide by looking at many properties together, not just one. Test: press a pencil lead hard against a table — it breaks; press a copper wire the same way — it bends. Lalit is right: conducting electricity alone doesn't make something a metal, and pencil lead is graphite, a non-metal that happens to conduct.
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