Chapter 3 Water and Life - Vocabulary

Vocabulary flashcards covering key terms from the Water and Life lecture (Chapter 3).

Water

A polar molecule (H2O) with two hydrogens and one oxygen; exists in solid, liquid, and gas states; expands upon freezing; solvent of life.

Hydrogen bond

A weak attraction between a hydrogen atom of one molecule and an electronegative atom (usually oxygen) of a neighboring molecule.

Polar covalent bond

A covalent bond in which electrons are shared unequally, creating partial charges and polarity.

Cohesion

Attraction among water molecules that holds them together, aiding transport in organisms.

Adhesion

Clinging of water to surfaces or other substances, assisting movement through vessels.

Surface tension

The energy required to stretch or break the surface of a liquid; high in water due to hydrogen bonding.

Specific heat

The amount of heat needed to raise the temperature of 1 g of a substance by 1°C; water’s is 1 cal/g/°C (high).

Heat of vaporization

The amount of heat required to convert 1 g of liquid to gas; water’s is high because hydrogen bonds must be broken.

Evaporation

Liquid molecules gain enough energy to overcome intermolecular attractions and become gas.

Evaporative cooling

Cooling of a liquid surface as high-energy molecules escape as vapor.

Solvent

The dissolving agent in a solution; water is a common solvent due to its polarity.

Solute

Substance dissolved in a solvent.

Hydration shell

A surrounding sphere of water molecules around a dissolved ion or molecule.

Aqueous solution

A solution in which water is the solvent.

Polar molecule

Molecule with an uneven distribution of charge due to polar bonds; water is polar.

Hydrophilic

Substances with affinity for water; water-loving; often ionic or polar.

Hydrophobic

Substances with little or no affinity for water; nonpolar; water-fearing.

Molarity (M)

One mole of solute per liter of solution.

Mole

Amount of substance containing 6.02×10^23 molecules; its mass in grams equals its molecular weight.

Avogadro’s number

6.02×10^23; number of particles per mole.

Molecular weight

Sum of atomic weights in a molecule; equals the molar mass in grams per mole.

Salt (NaCl) dissociation

In water, NaCl dissociates into Na+ and Cl− ions; example of solvation and ion hydration.

Hydronium ion

H3O+; water with an extra proton in acid-base reactions.

Hydrogen ion

H+; a proton released in acid-base reactions; increases acidity.

pH

Scale (1–14) measuring hydrogen ion concentration; 7 is neutral at 25°C.

Acid

Substance that increases H+ concentration in solution.

Base

Substance that decreases H+ concentration, often by accepting H+ or releasing OH−.

Strong acid

Dissociates completely in water (e.g., HCl).

Weak acid

Dissociates partially in water; equilibrium exists (e.g., carbonic acid).

Strong base

Dissociates completely in water (e.g., NaOH).

Weak base

Accepts H+ or dissociates partially (e.g., NH3).

Buffer

A solution that resists pH changes by absorbing or releasing H+; often a weak acid/base pair (e.g., carbonic acid/bicarbonate).

Carbonic acid

H2CO3; weak acid formed when CO2 dissolves in water.

Bicarbonate

HCO3−; conjugate base of carbonic acid; important in buffering in blood.

Ocean acidification

Lowering of seawater pH due to CO2 dissolution forming carbonic acid.

Carbonate ion

CO3^2−; essential for calcifying organisms; decreases as CO2 increases in oceans.

Ice density anomaly

Ice is less dense than liquid water, so ice floats and insulates aquatic environments.