Question

water has surface tension because...

• molecules at the surface make more hydrogen bonds.
• water tends to evaporate from the surface.
• hydrogen bonds between surface water molecules resist being stretched.
• there is positive pressure inside the water mass.
• cohesion forces are weaker at the surface

part f
which of the following helps most to explain why water has a high specific heat?

• (a) a water molecule can make 4 hydrogen bonds.
• (b) the water molecule has exceptionally strong covalent bonds.
• (c) water temperature is exceptionally sensitive to heat.
• both (a) and (b).
• both (b) and (c).

Explanation:

For the first question, surface tension in water is due to hydrogen - bonds between surface water molecules that resist being stretched. Molecules at the surface have fewer neighbors above them, so they form stronger hydrogen - bonds with their adjacent molecules. Evaporation is not the cause of surface tension, positive pressure inside the water mass is not relevant, and cohesion forces are stronger at the surface in the context of surface tension.
For the second question, water has a high specific heat because a water molecule can make 4 hydrogen bonds. These hydrogen bonds require a significant amount of energy to break when heat is added, thus water can absorb a large amount of heat before its temperature rises. The covalent bonds in water are not the main factor for high specific heat, and water is not exceptionally sensitive to heat in the sense of having a low specific heat.

Answer:

First question: hydrogen bonds between surface water molecules resist being stretched.
Second question: (a) A water molecule can make 4 hydrogen bonds.