Properties of Water and Hydrogen Bonding

Vocabulary flashcards covering hydrogen bonding, physical properties, thermal behavior, solvent abilities, and chemical dissociation of water.

Hydrogen Bond

A weak attraction between a partially positive hydrogen atom covalently bonded to an electronegative atom and a nearby electronegative atom carrying a partial negative charge.

Polar Molecule

A molecule with uneven distribution of charges, leading to distinct positive and negative regions; enables formation of hydrogen bonds (e.g., water).

Cohesion

The tendency of water molecules to stick to each other due to hydrogen bonding, driving phenomena like water column formation in plants.

Adhesion

The tendency of water molecules to stick to other polar surfaces or materials, aiding water movement up plant vessels.

Surface Tension

The difficulty of breaking the surface of a liquid; in water, extensive hydrogen bonding creates exceptionally high surface tension that supports insects like water striders.

Crystalline Ice Lattice

Open, hydrogen-bonded structure in solid water where each molecule bonds to four others, making ice less dense than liquid water.

Density Anomaly of Water

Condition in which liquid water is denser than solid ice, allowing ice to float and insulate aquatic life below.

Specific Heat

Amount of heat required to raise the temperature of 1 g of a substance by 1 °C; water’s value (1 cal g⁻¹ °C⁻¹) is unusually high because heat energy first breaks hydrogen bonds.

Thermal Stability of Water

Water’s resistance to rapid temperature change due to high specific heat, moderating climate and protecting cellular processes.

Hydrophilic Molecule

‘Water-loving’ substance that is polar or charged and readily forms hydrogen bonds with and dissolves in water.

Hydrophobic Molecule

‘Water-fearing’ substance that is non-polar, lacks charge regions, and minimizes contact with water (e.g., oils).

Hydrophobic Effect

Tendency of non-polar molecules to aggregate in aqueous solution as water excludes them, driving protein folding and membrane formation.

Solvent Property of Water

Water’s ability to dissolve many polar or charged substances because it surrounds them with hydrogen-bonding interactions.

Ammonia Dissolution in Water

Process where polar NH₃ molecules form hydrogen bonds with water, becoming surrounded and diluted despite ammonia’s toxicity.

Water Dissociation

Occasional splitting of H₂O into a hydrogen ion (H⁺) and a hydroxide ion (OH⁻), foundational to pH and acid–base chemistry.

Hydrogen Ion (H⁺)

Proton produced when a water molecule dissociates; contributes to acidity in solutions.

Hydroxide Ion (OH⁻)

Negatively charged ion produced alongside H⁺ during water dissociation; contributes to basicity.