Water and pH

Practice vocabulary flashcards based on lecture notes covering the chemical properties of water, its role as a solvent, and the dynamics of pH and buffer systems.

Hydrophilic

A substance that interacts readily with or dissolves in water, derived from the words for "water-loving."

Hydrophobic

Non-polar molecules, such as oils and fats, that do not interact well with water and separate from it rather than dissolving; also known as "water-fearing."

Solvent

A substance capable of dissolving other molecules.

Solute

The substance that is dissolved in a liquid.

Solution

The mixture formed when a solute is dissolved in a solvent.

Aqueous solution

A solution where the solvent is water.

Sphere of hydration

Also known as a hydration shell, this is the surrounding of particles by water molecules that serves to keep them separated in water.

Dissociation

The process where individual ions react with water molecules and their ionic bonds are disrupted, such as when $NaCl$ dissociates into $Na^+$ and $Cl^-$ ions.

pH

A measure of the concentration of hydrogen ions ($[H^+]$) in a solution, calculated as the negative of the base $10$ logarithm of the $[H^+]$ concentration.

Hydronium ion

The ion ($H_3O^+$) formed when hydrogen ions ($H^+$) are immediately attracted to water molecules in liquid water.

Neutral pH

A pH of $7.0$, derived from the concentration of hydrogen ions dissociating from pure water ($1 \times 10^{-7}$ moles per liter).

Acid

A substance that increases the $[H^+]$ concentration in a solution by having hydrogen atoms dissociate; stronger examples donate $H^+$ more readily.

Base

Also referred to as alkaline, it is a substance that decreases the $[H^+]$ concentration in a solution by providing $OH^-$ or other ions that combine with hydrogen ions.

pH scale

A scale ranging from $0$ to $14$, where anything below $7.0$ is acidic and anything above $7.0$ is basic.

Buffer

A substance or system that readily absorbs excess $H^+$ or $OH^-$, keeping the pH of cells in homeostasis.

Carbonic acid

A component of the human blood buffer system ($H_2CO_3$) that can be converted to carbon dioxide gas and exhaled to prevent blood pH from dropping dangerously.

Bicarbonate ion

A component of the human blood buffer system ($HCO^-$) that combines with free hydrogen ions to moderate pH increases.

Homeostasis

The maintenance of stable internal conditions, such as near-neutral pH, required for an organism's survival.

Kinetic energy

The energy of motion in water molecules produced by heat, which causes hydrogen bonds to break during state changes like boiling.