The element with electronic configuration 2,8,6 belongs to: MCQ with Answer and Explanation

Explanation:
Fermentation of sugar (glucose) by yeast produces ethanol and carbon dioxide—new substances are formed, so it's a chemical change. Melting, boiling are physical state changes. Magnetization aligns domains but does not change chemical composition. Chemical changes involve breaking and forming of bonds. Indicators: gas evolution, color change, heat, precipitate.

Explanation:
According to the law of conservation of mass, the mass of a substance remains constant during any physical change, including the interconversion of states. Density, volume, and shape change as the intermolecular spaces and arrangement alter during phase transitions, but the total number of atoms and mass is conserved.

Explanation:
Smelting involves heating a metal oxide ore (roasted or calcined) with a reducing agent like coke (carbon) or CO to obtain the metal in the molten state. Example: Fe₂O₃ + 3CO → 2Fe + 3CO₂ in blast furnace. Calcination: heating carbonate/ hydroxide ore in absence of air. Roasting: heating sulfide ore in excess air. Leaching: chemical dissolution of ore. Smelting is a key pyrometallurgical step.