Describe the chemical properties of water.

Water reacts with a large number of substances. Some of the important reactions are given below.
$(i)$ Amphoteric Nature: It has the ability to act as an acid as well as a base,i.e.,it behaves as an amphoteric substance. In the Br\u00f6nsted sense,it acts as an acid with $NH_{3}$ and a base with $H_{2}S$.
$H_{2}O_{(l)} + NH_{3(aq)} \rightleftharpoons OH^{-}_{(aq)} + NH_{4(aq)}^{+}$
$H_{2}O_{(l)} + H_{2}S_{(aq)} \rightleftharpoons H_{3}O^{+}_{(aq)} + HS^{-}_{(aq)}$
The auto-protolysis (self-ionization) of water takes place as follows:
$H_{2}O_{(l)} + H_{2}O_{(l)} \rightleftharpoons H_{3}O^{+}_{(aq)} + OH^{-}_{(aq)}$
$(ii)$ Redox Reactions Involving Water: Water can be easily reduced to dihydrogen by highly electropositive metals.
$2H_{2}O_{(l)} + 2Na_{(s)} \longrightarrow 2NaOH_{(aq)} + H_{2(g)}$
Thus,it is a great source of dihydrogen. Water is oxidised to $O_{2}$ during photosynthesis.
$6CO_{2(g)} + 12H_{2}O_{(l)} \longrightarrow C_{6}H_{12}O_{6(aq)} + 6H_{2}O_{(l)} + 6O_{2(g)}$
With fluorine also,it is oxidised to $O_{2}$:
$2F_{2(g)} + 2H_{2}O_{(l)} \longrightarrow 4H^{+}_{(aq)} + 4F^{-}_{(aq)} + O_{2(g)}$