Pencil 'lead' is a mixture of graphite and clay. Graphite's layered structure allows it to leave marks on paper. Diamond is too hard and would tear paper. Fullerene is a nanomaterial, not for writing. Charcoal is used for drawing but not pencils.
Explanation:
Diamond has a rigid 3D covalent network, making it the hardest natural material. It does not conduct electricity (no free electrons). It is not layered (graphite is). It is used as an abrasive, not a lubricant.
Explanation:
A negative catalyst (inhibitor) decreases the rate of a reaction by increasing activation energy or destroying active intermediates. Example: phosphoric acid inhibits H₂O₂ decomposition. Positive catalysts speed up, enzymes are biocatalysts, autocatalysts are products that catalyze their own formation.
Explanation:
Detergents emulsify grease by forming micelles around oil droplets, removing them from fabric. Soap does same but less effective in hard water.
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