Understanding:
• Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water
Water has the capacity to form intermolecular associations with molecules that share common properties
Because water is polar it will be attracted to other molecules that are polar or have an ionic charge
Cohesive Properties:
- Cohesion is the ability of like molecules to stick together
- Water is strongly cohesive (it will form hydrogen bonds)
Adhesive Properties:
- Adhesion is the ability of dissimilar molecules to stick together
- Water will form intermolecular associations with polar and charged molecules
Significance of Cohesive and Adhesive Properties:
The cohesive properties of water explain its surface tension
- The hydrogen bonding between water molecules allows the liquid to resist low levels of external force (surface tension)
- The high surface tension of water makes it sufficiently dense for certain smaller organisms to move along its surface
The adhesive properties of water explain its capillary action
- Attraction to charged or polar surfaces (e.g. glass) allows water to flow in opposition of gravitational forces (capillary action)
- This capillary action is necessary to allow water to be transported up plant stems via a transpiration stream
Cohesion and Adhesion by Water Molecules
