Which of the following was proposed by Rutherford's alpha-particle scattering experiment? MCQ with Answer and Explanation

Explanation:
Smelting is a reduction process, not concentration. Concentration (beneficiation) methods include gravity separation, magnetic separation, froth flotation, and leaching (chemical). Smelting involves heating concentrated ore with a reducing agent to extract metal. For example, hematite concentrated by washing, then smelted in blast furnace.

Explanation:
In displacement reactions, a more reactive element displaces a less reactive one from its compound. Here, iron (more reactive than copper) displaces copper from copper sulfate. A is combination; B is decomposition; D is neutralization (double displacement).

Explanation:
Physical changes alter the form, state, or appearance without changing chemical identity. They are usually easily reversible (e.g., freezing/melting). Chemical changes produce new substances and are often irreversible (e.g., burning). Physical: crushing, dissolving, boiling. Chemical: rusting, cooking, digestion.