Water and Life (Chapter 3) - Key Terms

Vocabulary flashcards covering key terms from Water and Life (Chapter 3) to help review concepts such as hydrogen bonding, water properties, pH, acids/bases, and solution chemistry.

Water

A polar molecule (H2O) essential for life; forms hydrogen bonds between molecules.

Polar molecule

A molecule with an uneven distribution of electron density, yielding partial charges.

Hydrogen bond

A weak attraction between a partially positive H of one molecule and a partially negative atom (e.g., O) of a neighboring molecule.

Cohesion

Attraction between like molecules, such as water molecules sticking to each other.

Adhesion

Attraction between water and other substances, e.g., plant cell walls.

Surface tension

Measure of how difficult it is to break the surface of a liquid; high in water due to hydrogen bonding.

Hydrophilic

Water-loving; substances that interact readily with water.

Hydrophobic

Water-fearing; nonpolar substances that do not mix well with water.

Solvent

The dissolving medium in a solution; water is a common biological solvent.

Solute

The substance dissolved in the solvent.

Solution

A uniform mixture of solute dissolved in solvent.

Hydration shell

A sphere of water molecules surrounding a dissolved ion.

Ion

A charged particle formed by loss or gain of electrons.

Acid

A substance that increases H+ concentration in solution by donating protons.

Base

A substance that decreases H+ or increases OH-, often accepting protons.

pH

A scale (0-14) measuring acidity; pH = -log10[H+].

Neutral

A solution with [H+] ≈ [OH−], pH around 7 at 25°C.

Buffer

A substance that minimizes pH changes by absorbing or releasing H+ or OH−.

Ocean acidification

Lowering of ocean pH due to CO2 dissolved in seawater forming carbonic acid.

Carbonic acid

H2CO3 formed when CO2 dissolves in water; dissociates to HCO3− and H+.,

Bicarbonate

HCO3−, a buffering species formed from carbonic acid.

Carbonate

CO3^2−, a buffering species formed at higher pH from carbonic acid.

Specific heat

Energy required to raise 1 g of a substance by 1°C; for water, 1 cal/(g·°C).

Heat of vaporization

Energy required to convert 1 g of liquid to gas.

Evaporative cooling

Cooling that occurs as a liquid evaporates, stabilizing temperature.

Ice density

Ice is less dense than liquid water, so it floats.

Floating of ice

Ice floats on liquid water due to its lower density from a crystalline structure.

Salt

Ionic compound that dissolves to form ions in water; e.g., NaCl.

Ionic bond

Bond formed by electrostatic attraction between oppositely charged ions.

Polar covalent bond

Covalent bond with unequal sharing of electrons, creating partial charges.

Nonpolar covalent bond

Covalent bond with equal sharing of electrons; no partial charges.

Electrolyte

Substance that dissociates into ions in water and conducts electricity.

Nonelectrolyte

Substance that dissolves in water but does not ionize well, poor conductor.

Mixture

Two or more substances physically intermingled; not chemically bound.

Heterogeneous

Mixture with nonuniform composition; components are not evenly distributed.

Homogeneous

Uniform mixture with constant composition throughout.

Avogadro's number

6.02 × 10^23; number of entities in one mole.

Mole

Amount of substance containing Avogadro's number of entities.

Molarity

M = moles of solute per liter of solution.

Molecular weight

Sum of atomic weights in a molecule; expressed in g/mol.