Which of the following metals is liquid at room temperature? MCQ with Answer and Explanation

Explanation:
The forces of attraction are minimum in gases, intermediate in liquids, and maximum in solids. Oxygen is a gas, water is a liquid, and sugar is a solid. Thus, the increasing order of intermolecular forces is oxygen < water < sugar, reflecting their respective physical states at room temperature.

Explanation:
Ammonium chloride (NH₄Cl) sublimes on heating—it directly converts from solid to vapor without passing through the liquid phase—while common salt (NaCl) remains as a solid residue. This property allows separation by sublimation. Filtration would not work because both are soluble in water, distillation is for liquids, and chromatography separates dissolved substances based on differential adsorption. Lab tip: NH₄Cl vapors condense on the cool funnel to give solid sublimate.

Explanation:
Endothermic reactions absorb heat from the surroundings. The decomposition of calcium carbonate (CaCO₃ → CaO + CO₂) requires continuous heating to proceed. Burning of gas, respiration, and the reaction of sodium with water are all exothermic reactions that release significant amounts of heat energy to the surroundings.