The basics (surface tension) (1 Viewer)

[HSC2014]

When you pour water into a glass, it concaves upwards due to Adhesive forces > cohesive forces near the edges of surface
But how can this be?
Adhesive forces in this case are dispersive whilst cohesives forces are hydrogen bonding? So dispersion > hydrogen bonding? !?!?!??!?

Edit: I think the flaw in my logic lies somewhere in the adhesive forces being 'dispersive' - since there exist 4 other forms: mechanical, chemical, electrostatic and diffusive. But they don't seem relevant.
Edit 2: Perhaps the answer is correct due to water's positioning at surface edges. There exists minimum hydrogen bonding whilst plentiful dispersion, so dispersion could overpower hydrogen bonding. Welp, food for thought.

 

[Trebla]

Haven't done Chemistry in a while but my understanding is as follows:
- Consider a beaker of water and a water molecule in the middle of the beaker at the surface of the water. If you imagine its surroundings for a fixed (but small) radius then the bottom half of its surroundings is basically other water molecules and the top half is air. Since the hydrogen bonding from the molecule of reference to the other water molecules below is stronger than its interaction with the air then the molecule feels a net downward attractive force
- Now consider the case where the water molecule is at the edge of the beaker in contact with the glass surface. This time there is half as much water in the 'southern hemisphere' of its surroundings compared to the previous scenario, hence the downwards attractive force driven by hydrogen bonding is not as strong as the case if it the molecule was right in the middle. The further away from the glass edge, the more water molecules there are in the surroundings, hence the greater the downward force which leads to the convex shape. It's not exactly the adhesion that is absolutely 'stronger' than the hydrogen bonding but more that the aggregated hydrogen bonding is less (due to less water molecules in the surroundings) compared to the centre of the water surface which then makes the adhesion a little more pronounced.