Breaking the hydrogen bond between two water molecules is called dissociation

That's incorrect. Breaking the hydrogen bond between two water molecules is not called dissociation. Dissociation refers to the process in which a compound breaks into its constituent ions when dissolved in water.

To break the hydrogen bond between two water molecules, you need to provide enough energy to overcome the attractive forces between them. This can be achieved through heating or other means of increasing the kinetic energy of the water molecules.

Water molecules are held together by hydrogen bonds, which are relatively weak forces of attraction between the hydrogen atom of one water molecule and the oxygen atom of another water molecule. These hydrogen bonds are responsible for many of the unique properties of water, such as its high boiling point, surface tension, and ability to dissolve a wide range of substances.

When enough energy is supplied to water molecules, the hydrogen bonds can be temporarily disrupted, allowing the molecules to separate from each other. However, it's important to note that the hydrogen bonds between water molecules are constantly forming and breaking, even at room temperature.