Explain why :

(a) water is an excellent liquid to use in cooling systems.

(b) a solution is always clear and transparent.

(c) lakes and rivers do not suddenly freeze in the winters.

(d) the solute cannot be separated from a solution by filtration.

(e) fused CaCl₂ or conc. H₂SO₄ is used in a desiccator.

(f) effervescence is seen on opening a bottle of soda water.

(g) Table salt becomes sticky on exposure to humid air during the rainy season.

Normally, solubility of a crystalline solid increases with temperature. Does it increase uniformly in all cases ? Name a substance whose solubility :

(a) increases rapidly with temperature.

(b) increases gradually with temperature.

(c) increases slightly with temperature.

(d) initially increases then decreases with rise in temperature.

In which of the following substances will there be :

(a) increase in mass

(b) decrease in mass

(c) no change in mass when they are exposed to air?

1. Sodium chloride
2. Iron
3. Conc. sulphuric acid
4. Table salt
5. Sodium carbonate crystals

State the methods by which hydrated salts can be made anhydrous?