Mystery #3Tier 3chemistry / solids
Why is a diamond so hard but pencil 'lead' so soft, when both are pure carbon?
Diamond is the hardest natural material on Earth: it can scratch glass and steel. The 'lead' in your pencil is so soft it crumbles onto paper just by dragging it along. Yet here's the twist: both are made of nothing but carbon atoms, the exact same ingredient. So how can the same stuff be the hardest thing going AND one of the softest?
Your guess
What's your hunch about how the same carbon can be super-hard as diamond yet soft as pencil lead?
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