Water - Physical and Chemical Properties

Water is a clear, colorless, odorless, and tasteless liquid with a neutral $pH$ of $7$.

Anomalous Expansion of Water: Unlike other liquids, water expands when cooled from $4^\circ C$ to $0^\circ C$. It reaches its maximum density of $1 \text{ g/cm}^3$ at $4^\circ C$.

Specific Heat Capacity: Water has a high specific heat capacity ($4.2 \text{ J/g}^\circ C$), which means it can absorb or release a large amount of heat with minimal temperature change.

Universal Solvent: Due to its polar nature, water can dissolve a wide variety of solutes, including solids, liquids, and gases.

Reaction with Metals: Reactive metals like sodium ($Na$) and potassium ($K$) react violently with cold water to produce hydroxides and hydrogen gas ($H_2$).

Formation of Acids and Bases: Non-metallic oxides like $CO_2$ and $SO_2$ dissolve in water to form acids, while metallic oxides like $CaO$ form bases (alkalis) such as $Ca(OH)_2$.

Hardness of Water: Hard water contains dissolved salts of calcium ($Ca^{2+}$) and magnesium ($Mg^{2+}$). Temporary hardness is caused by bicarbonates ($HCO_3^-$), while permanent hardness is caused by chlorides ($Cl^-$) and sulfates ($SO_4^{2-}$).

Water of Crystallization: This is the fixed number of water molecules chemically combined in a dry crystal, such as in Blue Vitriol ($CuSO_4 \cdot 5H_2O$).