Properties of Water

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by

• hydrogen bonds

• nonpolar covalent bonds

• polar covalent bonds

• ionic bonds

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?

• a covalent bond

• a hydrogen bond

• an ionic bond

• a hydrophilic bond

• a van der waals interaction

The partial negative charge in a molecule of water occurs because

• the oxygen atom acquires an additional electron

• the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

• the oxygen atom has two pairs of electrons in its valence shell that are not neutralized by hydrogen atoms

• the oxygen atom forms hybrid orbitals that distribute electrons unequally around the oxygen nucleus

• one of the hydrogen atoms donates an electron to the oxygen atom

Water molecules are able to form hydrogen bonds with

• compounds that have polar covalent bonds

• oils

• oxygen gas (O2 molecules)

• Chloride ions

• any compound that is not soluble in water

Which type of bond must be broken for water to vaporize?

• ionic bonds

• both hydrogen bonds and ionic bonds

• polar covalent bonds

• hydrogen bonds

• both polar covalent bonds and hydrogen bonds

Why does evaporation of water from a surface cause cooling of the surface?

• The breaking of bonds between water molecules absorbs heat

• The water molecules with the most heat energy evaporate more readily

• The solute molecules left behind absorb heat

• Water molecules absorb heat from the surface in order to acquire enough energy to evaporate

• The expansion of water vapor extracts heat from the surface

Which of the following effects is produced by the high surface tension of water?

• Lakes don't freeze solid in winter, despite low temperatures

• A water strider can walk across the surface of a small pond

• Water flows upward from the roots to the leaves in plants

• Organisms resist temperature changes, although they give off heat due to chemical reactions

• Evaporation of sweat from the skin helps to keep people from overheating

Why does ice float in liquid water?

• The high surface tension of liquid water keeps the ice on top

• The ionic bonds between the molecules in ice prevent the ice from sinking

• Ice always has air bubbles that keep it afloat

• Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of the liquid water

• The crystalline lattice of ice causes it to be denser than liquid water

Hydrophobic substances such as vegetable oil are

• nonpolar substances that repel water molecules

• nonpolar substances that have an attraction for water molecules

• polar substances that repel water molecules

• polar substances that have an affinity for water

• charged molecules that hydrogen-bond with water molecules

Based on your knowledge of the polarity of water molecules, the solute molecule depicted here is most likely

• positively charged

• negatively charged

• without charge

• hydrophobic

• nonpolar