Hydrogen bonds contribute to many of the unique features of water.
Among the various kinds of weak chemical bonds, hydrogen bonds are so important in the chemistry of life that they deserve
special attention.
In living organisms, most of the strongest chemical bonds are covalent ones, which link atoms to form a cell's molecules.
But weaker bonding within and between molecules is also indispensable in the cell, where the properties of life emerge from such interactions. The most important large biological molecules are held in their functional form by weak bonds. In addition, when two molecules in the cell make contact, they may adhere temporarily by weak bonds. The reversibility of weak bonding can be an advantage: Two molecules can come together, respond to one another in some way, and then separate. Several types of weak chemical bonds are important in living organisms. One is the ionic bond, another type of weak bond, crucial to life, is known as a hydrogen bond.
Hydrogen bonds: Among the various kinds of weak chemical bonds, hydrogen bonds are so important in the chemistry of life that they deserve special attention. A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom. Hydrogen bonds contribute to many of the unique features of water.
The state in which liquid water molecules are stuck together, via H–bonding, gives water a physical property termed cohesion. Due to cohesion, water has a high surface tension(resistance to disruption at the surface). This property is exploited by many insects (e.g., the stone fly pictured below) and some vertebrates (e.g., the basilisk lizard), which can actually stand or run on water without breaking the surface and falling through. A hydrogen bond results from the attraction between the partial positive charge on the hydrogen atom of water and the partial negative charge on the nitrogen atom of ammonia.
Van der Waals interactions
Van der Waals forces are driven by induced electrical interactions between two or more atoms or molecules that are
very close to each other.
Van der Waals interactions: Van der Waals forces are driven by induced electrical interactions between two or more atoms or molecules that are very close to each other. Van der Waals interaction is the weakest of all intermolecular attractions between molecules. However, with a lot of Van der Waals forces interacting between two objects, the interaction can be very strong.