Final answer:
The 4J energy required for a water molecule to evaporate is due to the overcome of weaker intermolecular forces such as hydrogen bonds, whereas the 400J needed to break a water molecule's O-H bond reflects the much stronger intramolecular covalent bonds.
Step-by-step explanation:
To explain the data using intramolecular vs. intermolecular forces, consider that intramolecular forces are the forces that hold atoms together within a molecule. For H2O, the intramolecular forces would be the covalent bonds between the hydrogen (H) atoms and oxygen (O). Breaking this bond demands a considerable amount of energy, about 400 kJ, which is indicative of the strength of intramolecular forces. In contrast, intermolecular forces are the forces that exist between molecules. The 4J of energy required for a liquid H2O molecule to escape and turn into a gas is considerably less than that required to break the O-H bond because these are intermolecular forces, such as hydrogen bonds, which are much weaker.
The heat of vaporization of water, represents the energy needed for liquid water to turn into water vapor, which requires overcoming these weaker intermolecular forces. Typically, intermolecular forces are weak compared to strong covalent bonds (intramolecular forces), explaining why substances can change states (solid, liquid, gas) without breaking molecular bonds. The provided data illustrates this concept, with a small amount of energy (4J) being able to liberate a water molecule from its liquid state, while a vastly larger amount of energy (400J) is needed to actually break the covalent bonds within an individual water molecule.