Let's analyze each statement about water to identify which one is FALSE.

Statement 1: "There is extensive intramolecular hydrogen bonding in the condensed phase."

This is FALSE. In water, hydrogen bonding is primarily intermolecular (between different water molecules), not intramolecular (within the same molecule). A single water molecule (H₂O) has a bent shape, but the hydrogen atoms are covalently bonded to the oxygen atom. Intramolecular hydrogen bonding typically occurs in larger molecules where a hydrogen atom is close to a highly electronegative atom (like O or N) within the same molecule, such as in ortho-nitrophenol. In liquid water or ice, the bonding is between the hydrogen of one molecule and the oxygen of another, which is intermolecular.

Statement 2: "Ice formed by heavy water sinks in normal water."

This is TRUE. Heavy water is D₂O (where D is deuterium, ²H). It has a higher density than normal water (H₂O). When D₂O freezes, the ice has a higher density than normal ice. Normal ice (from H₂O) floats on water because it is less dense, but ice from D₂O is denser and thus sinks in normal water.

Statement 3: "Water can act both as an acid and as a base."

This is TRUE. Water is amphoteric. It can act as an acid (donate a proton) or as a base (accept a proton). For example:
As an acid: $H_{2}O+{\mathrm{NH}}^2-\to {\mathrm{OH}}^{\mathrm{-}}+{\mathrm{NH}}_3$
As a base: $H_{2}O+{\mathrm{HCl}}_{\mathrm{}}\to H_3{O}^{\mathrm{+}}+{\mathrm{Cl}}^{\mathrm{-}}$

Statement 4: "Water is oxidized to oxygen during photosynthesis."

This is TRUE. In the light-dependent reactions of photosynthesis, water molecules are split (photolysis) in a process called oxidation, releasing oxygen gas, protons, and electrons. The half-reaction is:
$2H_{2}O\to O_2+4H^{\mathrm{+}}+4e^{\mathrm{-}}$

Final Answer

The FALSE statement is: "There is extensive intramolecular hydrogen bonding in the condensed phase."

Related Topics & Formulae

Hydrogen Bonding: A special type of intermolecular force between a hydrogen atom (covalently bonded to a highly electronegative atom like O, N, F) and another electronegative atom. It is responsible for water's high boiling point, surface tension, and the fact that ice floats.

Amphoteric Substances: Substances that can act as both an acid and a base. Water is a classic example. The autoionization of water is given by: $2H_{2}O\to H_3{O}^{\mathrm{+}}+{\mathrm{OH}}^{\mathrm{-}}$, with an equilibrium constant K_w = [H₃O⁺][OH⁻] = 1.0 × 10^-14 at 25°C.

Heavy Water (D₂O): Water in which the hydrogen atoms are replaced by deuterium. It has a higher molecular mass and density than H₂O, and its physical properties (like melting and boiling points) are slightly different.