What does cohesion refer to in a substance?

Cohesion refers to the attractive forces between molecules of the same substance, which leads to them sticking together. This phenomenon occurs due to intermolecular forces such as hydrogen bonding or van der Waals forces. In water, for example, the cohesion between water molecules is responsible for several important properties, such as the formation of water droplets and the ability of water to move through plants in a process called capillary action.

The other options address different interactions: one discusses the interaction between different substances, which is known as adhesion, while another mentions forces that separate particles, which would be related to repulsive interactions rather than cohesive ones. Lastly, the energy required to break molecular bonds pertains more to the concept of bond strength and stability than to the definition of cohesion itself. Thus, the focus on cohesive forces that unite particles within the same substance is what makes the correct answer relevant to the concept.