2020 Chemistry of Life & Water

40 vocabulary flashcards covering key concepts from the lesson on the chemistry of life and water.

Water (H2O)

A polar molecule formed by two hydrogen atoms bound to one oxygen; forms hydrogen bonds with itself and other substances.

Hydrogen bond

A weak attraction between a partially positive hydrogen atom in one molecule and a partially negative atom (usually O or N) in another molecule.

Polar covalent bond

A bond in which electrons are shared unequally between atoms, creating partial charges (as in O–H in water).

Nonpolar covalent bond

A bond in which electrons are shared equally between atoms (as in many hydrocarbons).

Ionic bond

An electrostatic attraction between oppositely charged ions.

Covalent bond

A bond formed by sharing electrons between atoms.

Cohesion

Attraction between water molecules due to hydrogen bonding; contributes to surface tension.

Adhesion

Attraction between water molecules and other substances; enables capillary action.

Surface tension

The cohesive forces at the surface of a liquid that make it behave as if its surface were covered with a thin skin.

Capillary action

Movement of water up narrow tubes against gravity due to cohesion and adhesion.

Solvent

Substance that dissolves solutes to form a solution; water is the universal solvent.

Solute

Substance dissolved in a solvent.

Solution

A homogeneous mixture of solute dissolved in solvent.

Hydrophilic

Water-loving; substances with attraction to water, typically polar or ionic.

Hydrophobic

Water-fearing; substances that lack attraction to water, usually nonpolar.

Hydration shell

A shell of water molecules surrounding dissolved ions or polar molecules.

Ice floats

Ice is less dense than liquid water due to its open crystal lattice, so it floats.

Specific heat

The amount of heat required to raise the temperature of a substance; water has a high specific heat.

Heat of vaporization

Energy required to convert liquid water to vapor; water has a high heat of vaporization.

Evaporative cooling

Cooling that occurs when water evaporates, removing heat from surfaces.

pH

A measure of how acidic or basic (alkaline) a solution is, based on H+ and OH− concentrations.

pH scale

A 0–14 scale where 7 is neutral; below 7 acidic, above 7 basic.

Acid

Substance that increases H+ concentration in solution, lowering pH.

Base

Substance that increases OH− concentration or decreases H+ concentration, raising pH.

Buffer

A system that resists pH changes by releasing or absorbing H+.

Ionization of water

Autoionization of water: H2O ⇌ H+ + OH−.

H+ and OH−

Hydrogen ion and hydroxide ion produced by water ionization; determine acidity/basicity.

Water as universal solvent

Water dissolves many substances due to its polarity, enabling many biological processes.

Polarity of water

Water molecules have partial charges (δ+ on H, δ− on O) due to unequal electron sharing.

Polar molecule

A molecule with regions of partial charge from uneven electron distribution.

Electronegativity

A tendency of an atom to attract electrons in a bond; higher for oxygen than hydrogen in water.

Hydrophobic interactions

Nonpolar regions clustering together and avoiding water due to unfavorable interactions.

Phospholipid membrane

A phospholipid bilayer forming cell membranes with hydrophilic heads outward and hydrophobic tails inward.

Hydrophilic phospholipid heads

Water-attracting regions of phospholipids that face the aqueous environment.

Hydrophobic phospholipid tails

Water-repelling regions of phospholipids that face inward, away from water.

Phospholipid head

The hydrophilic, phosphate-containing region of a phospholipid.

Plasma membrane

The cell membrane composed of a phospholipid bilayer surrounding the cell.

Polar molecule

A molecule with an uneven distribution of charge, such as water.

Transpiration

Water loss from plants via evaporation from leaves, driven by cohesion and adhesion.

Ice density anomaly

Ice is less dense than liquid water, allowing ice to float and insulate water below.

Ice crystal lattice

The ordered arrangement of water molecules in solid ice due to hydrogen bonding.

Van der Waals forces

Weak intermolecular forces arising from transient dipoles, important for nonpolar interactions.

Solubility

The ability of a substance to dissolve in a solvent.

Solvation

Process of surrounding solute particles with solvent molecules (e.g., water around ions).