Explanation:
James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles, which emitted a highly penetrating radiation consisting of neutral particles with mass similar to protons. Thomson discovered the electron, Rutherford the proton, and Dalton proposed the foundational atomic theory of matter.
Explanation:
Joseph Proust proposed the law of definite proportions (constant composition) – a given compound always contains the same elements in the same proportion by mass. Dalton's theory explained it. Lavoisier gave law of conservation of mass. Rutherford discovered nucleus.
Explanation:
Salt is soluble in water, sand is not. Add water, stir to dissolve salt, filter to separate sand. Then evaporate the filtrate to recover salt. Sublimation separates sublimable solids (NH₄Cl, naphthalene). Magnetic for magnetic materials. Fractional distillation for liquid mixtures. This is a standard separation technique.
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