States of Matter

This is the correct option. Distilled water has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.

This is the correct option. Evaporation changes water from liquid to gaseous state slowly. It is a continuous process that takes place at all places. 

This is a statement of a fact (present). Hence, poisitve degree of the verb (singular) is required. Thus, option 2.

Solvent action of water is called plumbosolvency.

Water is the only common substance that naturally exists in all three states of matter - solid (ice), liquid (water), and gas (water vapor) at Earth's surface temperatures. Ice is solid water, not a separate substance.

Gas has the lowest density among the options listed. Gases have molecules far apart with minimal attraction, resulting in very low mass per unit volume compared to liquids (water) and solids (sand, dust).

Dehydration is the process of removing water from substances. In biological contexts, it means harmful water loss from the body. In food preservation, it means removing moisture to prevent bacterial growth. The suffix '-tion' indicates a removal process.

This is the correct option. Wood is not an optical medium. Light energy cannot pass through wood.

Smoke is the correct option, as it is a heterogeneous medium. An optical medium which has different compositions at different points is called a heterogeneous medium.

This is the correct option. Glass is a homogenous mixture. It has a uniform composition.

(i) Crystallization of sodium chloride - physical change (ii) Melting of ice - physical change (iii) Souring of milk - chemical change 

Methanol and water form a homogeneous mixture because they are completely miscible in all proportions, forming a single-phase solution. The other options are heterogeneous mixtures: starch and sugar (different particles), graphite and charcoal (distinct forms of carbon), calcium carbonate and calcium bicarbonate (separate solid compounds). Homogeneity means uniform composition throughout.

Water reaches its maximum density at 4°C. When heated from 0°C to 4°C, the volume decreases as density increases. From 4°C to 20°C, the volume increases normally as density decreases with heating. This anomalous expansion is unique to water.

According to the regelation phenomenon, increased pressure lowers the melting point of ice. When two ice blocks are pressed together, the contact point experiences high pressure, causing local melting. Water formed lubricates the surface, and when pressure is released, it refreezes, joining the blocks.

An emulsion is a colloid where one liquid is dispersed in another immiscible liquid. Examples include milk (fat in water), mayonnaise (oil in water), and butter (water in oil). A gas in liquid is foam, liquid in gas is aerosol, and gas in solid is solid foam.