Water: The Secret of Life

Flashcards on chemical bonds, electronegativity, and the properties of water.

Chemical bonds

Attractions between atoms that result in the sharing or exchange of electrons

Covalent bonds

Sharing of electrons

Polar covalent bond

Unequal sharing of electrons, resulting in partial charges

Nonpolar covalent bond

Equal sharing of electrons

Ionic bonds

Donated electrons

Hydrogen bonds

Attractions between molecules (not true bonds)

Electronegativity

An atom's attraction for electrons

Highly electronegative atoms

Oxygen and Nitrogen

Weakly electronegative atoms

Carbon and Hydrogen

Hydrogen bond

Forms when a partial positive hydrogen atom is attracted to another partial negative atom

Cations

Positively charged ions

Anions

Negatively charged ions

Salts

Ionic compounds (cation + anion)

Cohesion

Attraction between water molecules

Adhesion

Attraction of water molecules to the environment

Ability to moderate temperature

The absorption of heat (energy) is related to the destabilization of H bonds

Expansion upon freezing

Ice floats in liquid water because hydrogen bonds in ice are more “ordered” making ice less dense.

Versatility as a solvent

Water can dissolve compounds made of ionic and nonionic polar molecules

Hydrophilic substance

Substance that has an affinity for water

Hydrophobic substance

Substance that does not have an affinity for water because they have nonpolar covalent bonds

Acids and Bases

Hydrogen ion (H+) is transferred from one water molecule to another, leaving behind a hydroxide ion (OH−)

Buffers

Substances that minimize changes in concentrations of H+ and OH− in a solution