Atomic radius increases down a group due to addition of new shells. Ionization energy, electronegativity, and electron affinity (generally) decrease down a group.
Explanation:
Soda-lime glass is produced by fusing silica (SiO₂) with sodium carbonate (Na₂CO₃) and calcium carbonate (CaCO₃) at high temperature. Na₂CO₃ acts as flux to lower melting point, CaCO₃ provides stability. Reaction: Na₂CO₃ + SiO₂ → Na₂SiO₃ + CO₂. Sodium chloride is not used. Potassium compounds make harder glass.
Explanation:
Burning of a candle involves combustion of wax (hydrocarbons) with oxygen to produce CO₂ and H₂O, a chemical change. The melting of wax is a physical change. Cutting wood is physical (size change). Freezing water is physical (state change). A chemical change results in new substances with different properties. Often irreversible.
Explanation:
Cu + 4HNO₃ (conc.) → Cu(NO₃)₂ + 2NO₂ + 2H₂O. Dilute HNO₃ gives NO instead of NO₂. Copper does not produce H₂ with HNO₃ because HNO₃ is an oxidizing acid.
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