Question

How our lives would be different if the molecular shape of water was linear (180° bond angle) instead of bent (104.5° bond angle).?

Answer 1

Water molecule has:

• Bent structure with lone pair of electrons on electronegative O atom,
• Due to lone pair-bond pair repulsions the H-O-H has a bent geometrical shape with bond angle of 104.5⁰.
• The O negative being electronegative pulls bonded electron pair form O-H towards itself attaining partial negative charge, and respective H atoms attains partial positive charge. Hence a permanent dipole moment is established in water molecule.
• Water is polar molecule
• The O atom of one molecule combines with H atom of another water molecule forming HYDROGEN BONDS, making water as liquid.
• The hydrogen bonds are very strong, but H bonds break if pressure is applied or at high temperature they break off, which is the reason that ice is melted when pressure is applied or temperature is high.
• Because the dipole is so strong in water, it is able to induce temporary dipoles even in non-polar molecules. Which makes it "universal solvent." Almost anything will dissolve in water, even if only to a very small extent.
• Thus, water is able to bring together a wide variety of substances, which is required for life.

See image (I)

But if water molecule is assumed to have bond angle of 180^o. See image (II)

• O-H bond will be polar
• O with negative charge and H with positive charge
• But as the two H atoms point in opposite directions the molecule will have net zero dipole, means linear water molecule will be non-polar.
• Non-polar (linear) water molecule, will not be able to dissolve any other substance.
• Hence it would not liquify except at quite high pressures, and it would probably not remain liquid over more than about a 20° C. temperature range at best.
• It may be gas at room temperature like CO2 ( a linear molecule)

• The hydrogen bonding formed in water results to the surface tension of liquid water, due to which water drop is formed. With 180 degree bond angle, water drops would not form if poured on a surface. The shape of rain drops would be different .
• Polar water is universal solvent, it dissolves all waste in human body which is excreted as urine. Non-polar water will not do so.

As a result the life could not exist, not only on earth but anywhere.