Properties of Water, Hydrogen Bonds, and pH

Vocabulary flashcards covering core terms from the lecture notes on water properties, bonding, cohesion/adhesion, hydrophilic/hydrophobic substances, and pH.

Water

A polar molecule with polar covalent bonds that give it an uneven distribution of electrical charge.

Polar covalent bond

A covalent bond where electrons are shared unequally, creating partial charges; in water, O–H bonds are polar.

Hydrogen bond

A weak attractive force between a hydrogen atom in one molecule and a highly electronegative atom (usually O or N) in another molecule.

Cohesion

Attraction between water molecules via hydrogen bonds, causing them to stick together.

Adhesion

Attraction between water and other substances via hydrogen bonds, causing water to stick to surfaces.

Hydrophilic

Water-loving; polar substances that dissolve in water.

Hydrophobic

Water-fearing; nonpolar substances that do not dissolve in water.

Ice density

Ice floats on water because hydrogen bonds form a lattice that makes ice less dense than liquid water.

pH

Potential of hydrogen ions; a logarithmic scale (0-14) measuring hydrogen ion concentration; 7 is neutral.

Hydrogen ion

A proton (H+); determines acidity of a solution.

Hydroxide ion

OH−; produced when water loses a proton; base concept.

Acid

A substance that increases the H+ concentration in solution, making it more acidic (pH < 7).

Base

A substance that decreases H+ concentration or increases OH−, making the solution basic (pH > 7).

Neutral

pH = 7; equal amounts of H+ and OH−.

Logarithmic scale

A scale in which each unit represents a tenfold change in hydrogen ion concentration.

Ionic bond

An electrostatic attraction between oppositely charged ions formed by transfer of electrons.

Covalent bond

A bond formed by sharing electrons to fill valence shells; can be polar or nonpolar.

Nonpolar covalent bond

A covalent bond in which electrons are shared equally, resulting in no partial charges.

Polar molecule

A molecule with uneven distribution of charge due to polar bonds.

Autoionization of water

Water molecules spontaneously dissociate to form small amounts of H+ (or H3O+) and OH− ions.

Temperature effect on hydrogen bonds

Heating water destabilizes hydrogen bonds, causing them to break and reform.