Which statement about true solutions is correct?

• A. A true solution forms when a substance is dissolved in a liquid, and its components cannot be mechanically separated.
• B. A solution can always be separated by filtration.
• C. A true solution cannot form in liquids.
• D. A solution remains unchanged by heat.

Answer: (A)

True solutions are homogeneous mixtures formed when a solute dissolves in a solvent, with the dissolved particles small enough to be invisible and uniformly distributed. Because the particles are at the molecular level, they don’t exist as separate bits that a filter can catch, so ordinary filtration won’t separate a true solution back into solute and solvent. To separate them you’d typically use methods like evaporation or distillation, not filtration. That’s why this statement is correct: a substance dissolves in a liquid to form a true solution, and the components aren’t removable by mechanical filtration. The other statements don’t fit because filtration won’t separate dissolved substances, true solutions can form in liquids (as with sugar in water), and heat can affect a solution by changing solubility or causing components to volatilize or precipitate.