Discuss the structure of water, and outline the properties that make it unique. What will be an ideal response?
Because of the way a water molecule’s oxygen electrons are distributed, the overall geometry
of the molecule is a bent or angular shape. The angle formed by the two hydrogen atoms and
the central oxy-gen atom is about 105°. The angular shape of the water molecule makes it
electrically asymmetrical. Each water molecule can be thought of as having a positive (1) end
and a negative (2) end. This is because protons of the hydrogen atoms—the positively
charged particles in the nucleus (center)—are left partially exposed when the negatively
charged electrons bond more closely to oxygen. The water molecule behaves something like
a magnet: its positive end attracts particles that have a negative charge, and its negative end
(or pole) attracts particles that have a positive charge. For this reason, water is called a polar
molecule. When water comes into contact with compounds whose elements are held together
by the attraction of opposite electrical charges (most salts, for example), the polar water
molecule will separate that compound’s component elements from each other. This explains
why water can easily dissolve so many other compounds. The polar nature of water also
permits it to attract other water molecules. When a hydrogen atom (the positive end) in one
water molecule is attracted to the oxygen atom (the negative end) of an adjacent water
molecule, a hydrogen bond forms. A hydrogen bond between molecules is about 5% to 10%
as strong as a covalent bond within a molecule. Hydrogen bonds link water molecules
together by electrostatic forces. Hydrogen bonds greatly influence the properties of water by
allowing individual water molecules to stick to each other, a property called cohesion.
Cohesion gives water an unusually high surface tension. Adhesion, the tendency of water to
stick to other materials, enables water to adhere to solids—that is, to make them wet.
Cohesion and adhesion are the causes of capillary action, the tendency of water to spread
through a towel when one corner is dipped in water.
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Indicate whether the statement is true or false
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Iron atoms, Fe, are better reducing agents than copper ions, Cu2+. In which direction do electrons flow when an iron nail is submerged in a solution of Cu2+ ions?
A) Electrons cannot flow from the nail to the Cu2+ ions because there is no conductor between the two. B) The electrons flow from the submerged nail to the copper ions in solution. C) The electrons flow from the positive charge on the nail to the negative charge on the nail. D) The electrons flow from the copper ions in solution to the submerged nail.