Properties of Water and Aqueous Solutions

Vocabulary flashcards covering the chemical and physical properties of water, concentration units, pH calculations, acids and bases, and environmental chemistry concepts from the lecture.

Polarity of Water

The structural property of water where the oxygen atom is more electronegative than hydrogen, creating partial negative charges near oxygen and partial positive charges near hydrogen, enabling hydrogen bonding.

Cohesion

Hydrogen bonding between water molecules that holds them together, helping water move up plant xylem and contributing to surface tension.

Adhesion

The attraction between water molecules and different substances, such as hydrogen bonding between water and plant cell walls.

Surface Tension

A measure of the skin-like surface of a liquid caused by cohesive forces arising from extensive hydrogen bonding.

Heat

The total kinetic energy of molecular motion in a body of matter.

Temperature

A measure of heat intensity representing the average kinetic energy of molecular motion.

Specific Heat

The amount of heat that must be absorbed or lost for $1\,\text{g}$ of a substance to change its temperature by $1^\circ\text{C}$.

Specific Heat of Water

$1\,\text{cal/g/}^\circ\text{C}$; a high specific heat due to hydrogen bonding that helps stabilize global climate and organismal body temperatures.

Evaporative Cooling

The reduction in temperature of a liquid's remaining surface during evaporation, occurring because hydrogen bonds break and absorb heat as molecules escape.

Density Maximum of Water

Water reaches its maximum density at $4^\circ\text{C}$; below this, ice forms an open hexagonal lattice due to ordered hydrogen bonds, making ice float.

Solution

A liquid that is a completely homogeneous mixture of two or more substances.

Solvent

The dissolving agent of a solution.

Solute

The substance that is dissolved in a solution.

Aqueous Solution

A solution in which water is the solvent.

Hydration Shell

A sphere of water molecules surrounding a dissolved ion, stabilizing it and promoting its dissolution in water.

Hydrophilic

Describing a polar or ionic substance that has an affinity for water.

Hydrophobic

Describing a nonpolar substance (such as oil) that lacks an affinity for water and is repelled by it.

Colloid

A stable suspension of fine particles in a liquid.

Molecular Mass

The sum of the atomic masses of all atoms in a molecule.

Mole

An exact quantity of a substance containing $6.02 \times 10^{23}$ elementary entities.

Avogadro's Number

$6.02 \times 10^{23}$, the number of entities in one mole that relates moles to particle counts.

Dalton (Da)

A unit of mass defined as $1/12$ the mass of a carbon-12 atom, where $1\,\text{Da} \approx 1\,\text{g/mol} \approx 1\,\text{amu}$.

Molarity (M)

A measure of solute concentration calculated as $M = \frac{\text{moles solute}}{\text{liters of solution}}$.

Arrhenius Acid

A substance that increases the concentration of hydrogen ions ($\text{H}^+$) in an aqueous solution.

Arrhenius Base

A substance that increases the concentration of hydroxide ions ($\text{OH}^-$) in an aqueous solution.

Autoionization of Water

The spontaneous process in which water self-ionizes to form hydronium ions ($\text{H}_3\text{O}^+$, often represented as $\text{H}^+$) and hydroxide ions ($\text{OH}^-$) in equal amounts at equilibrium.

pH Scale

A logarithmic scale defining the acidity or basicity of a solution, mathematically calculated as $\text{pH} = -\log_{10}[\text{H}^+]$.

Buffer

An acid-base pair that reversibly binds $\text{H}^+$, resisting rapid changes in solution pH when acid or base is added.

Acid Precipitation

Rain, snow, or fog with a $\text{pH} < 5.6$, produced by atmospheric pollutants forming acids.

Ocean Acidification

The process where atmospheric $\text{CO}_2$ dissolves in seawater to form carbonic acid, lowering ocean pH and reducing carbonate ion ($\text{CO}_3^{2-}$) availability needed for calcification in marine organisms.