Chapter 19, Problem 9RAT

What is the boiling temperature of a single water molecule? Does this question make sense?

a) Boiling involves the separation of many molecules (plural). With only one molecule, the concept of boiling is meaningless.

b) Yes, this question does make sense because temperature measures the average kinetic energy of a molecule, which is $\text{100}°\text{C}$ for water.

c) $\text{100}°\text{C}$ indicates when the covalent bonds of the water molecule have been broken to give rise to hydrogen and oxygen atoms, which are released into atmosphere.

d) No, this question does not make sense because you need at least two molecules to get the average kinetic energy.

To determine

The boiling temperature of a single water molecule

Answer to Problem 9RAT

The best answer is option (d) as atleast two molecules are required to get the average kinetic energy, so the question does not make sense.

Explanation of Solution

Boiling point of a liquid is the temperature at which the liquid starts to boil and converts into vapour form.

Water boils at $\text{100°C}$, so the heat provides the sufficient energy to break the hydrogen bonds between the water molecules hence the intermolecular forces decreases. Also the average kinetic energy between two molecules increases on heating which allow the molecules to become free from each other’s vicinity and turn into vapour phase.

So the statement that boiling temperature of a single water molecule is of no sense as atleast two molecules are required to get the average kinetic energy and the hydrogen bonds.

Conclusion:

Therefore, the best answer is option (d).