matter-states-and-changes-l2 MCQ — 10 अभ्यास प्रश्न उत्तर सहित

Explanation

The hard item asks for the strongest rule, not a memorised example. New substance formation with changed properties is the central evidence for chemical change. Reversibility, heat and gas formation can help, but each can mislead when used alone.

Explanation

This item separates classification from everyday difficulty. Rusting forms a new substance, tearing changes form, and melting changes state. Dissolving salt is treated as physical at this level because the salt can be recovered and no new substance is required.

Explanation

Evaporation is not the same as boiling. The reason supports the assertion because a surface process can happen during drying of clothes or open water without the whole liquid boiling. This is a frequent REET-style trap around heat words.

Explanation

The assertion-reason pair tests hierarchy. A solution is not outside the mixture family; it is a uniform mixture. The reason explains the assertion because a solute distributed through a solvent gives more than one substance in one uniform phase.

Explanation

The match-list format rewards direction recall. The correct sequence follows the order given in the stem: melting, freezing, condensation and sublimation. It also prevents the common error of treating condensation and evaporation as the same word.