Water and Hydrogen Bonding

Flashcards covering water polarity, hydrogen bonding, examples beyond water (DNA base pairing), and the concepts of cohesion, adhesion, and surface tension.

What makes a water molecule polar?

Unequal sharing of electrons between oxygen and hydrogen, giving a partial negative charge on the oxygen and partial positive charges on the hydrogens.

Are hydrogen bonds intramolecular or intermolecular?

Intermolecular bonds between separate molecules; they are weaker than covalent or ionic bonds.

In a hydrogen bond, which parts of the water molecule participate?

The partially negative oxygen of one molecule and the partially positive hydrogens of another molecule form hydrogen bonds.

Give an example of hydrogen bonding between molecules besides water.

Hydrogen bonds between nitrogenous bases, such as adenine and thymine in DNA.

Hydrogen bonds are essential to the structure of which biomolecules?

DNA, RNA, and proteins.

Define cohesion.

Attraction between like molecules (e.g., water–water) due to hydrogen bonding.

Define adhesion.

Attraction between unlike molecules (e.g., water molecules sticking to a surface).

Define surface tension.

The cohesive force at the surface of a liquid that causes a surface to behave as if it were covered with a stretched membrane; largely due to hydrogen bonding among surface water molecules.

How do hydrogen bonds compare in strength to covalent bonds?

Hydrogen bonds are weaker than covalent bonds (and also weaker than ionic bonds), but are crucial for holding biological structures together.