Chapter 3: Water and Life — Vocabulary Flashcards

Vocabulary flashcards covering key water-related concepts from Chapter 3: properties of water, phase changes, polarity, hydrogen bonding, solubility, pH, acids/bases, buffers, and ocean–climate interactions.

Three phases of water

Water exists on Earth as solid (ice), liquid (water), and gas (water vapor).

Polarity of water

Water is a polar molecule because oxygen is highly electronegative, creating partial negative charge near O and partial positive near H.

Hydrogen bond

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

Cohesion

Attraction between water molecules due to hydrogen bonding, causing them to stick together.

Adhesion

Attraction between water molecules and other surfaces or molecules.

Surface tension

a measure of how difficult it is to break the surface of a liquid

Hydration shell

A layer of water molecules arranged around a dissolved ion or polar molecule.

Solvent

The dissolving agent of a solution;

Solute

The substance dissolved in a solvent.

Aqueous solution

A solution in which water is the solvent.

Hydrophilic

Water-loving; polar or charged substances dissolve readily in water.

Hydrophobic

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

Heat of fusion

Energy required to change a solid into a liquid at its melting point.

Specific heat

Amount of heat required to raise the temperature of 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 water to vapor.

Evaporative cooling

Cooling effect that occurs when water evaporates, removing heat from surfaces (e.g., sweating).

Ice density anomaly

Ice is less dense than liquid water and expands when it freezes, causing ice to float.

Density maximum at 4°C

Water is densest near 4°C; as it cools toward 0°C it becomes less dense and forms ice.

pH scale

A 0–14 scale measuring acidity/alkalinity; 7 is neutral.

Acid

A substance that donates hydrogen ions (H+) into solution.

Base

A substance that increases OH− or accepts H+; raises pH.

Hydronium ion

H3O+; a water molecule that has gained a proton, representing acidity.

Hydroxide ion

OH−; negatively charged species that contributes to basicity.

Buffer

A solution that resists pH changes by neutralizing added acids or bases.

Carbonic acid–bicarbonate buffer

Buffer system in blood and some oceans; CO2 forms carbonic acid that equilibrates with bicarbonate and H+ to maintain pH.

Ocean acidification

Increased CO2 in seawater lowers pH and reduces carbonate availability for shells and corals.

Salt dissolution in water / aqueous solution

Ionic compounds dissolve as water molecules hydrate the ions (e.g., Na+ and Cl− around ions).

Hydration shell around ions

Water molecules orient around dissolved ions due to partial charges, stabilizing the ions.

Phase change terms

Melting (solid to liquid), freezing (liquid to solid), evaporation (liquid to gas), condensation (gas to liquid); energy changes accompany each.

Calories vs kilocalories

A calorie is the energy to raise 1 g of water by 1°C; a kilocalorie (Calorie) is 1000 calories and is used in nutrition.

2 most important characteristics of water are

water exist in all 3 phases on earth

water molecules are polar

4 emergent properties of water

cohesive and adhesive behavior

ability to moderate temp

expansion upon freezing

versatility as a solvent