Lecture 3: Water and Its Life-Supporting Properties

A set of vocabulary flashcards based on Lecture 3 covering water properties, thermal concepts, solution chemistry, and acids and bases.

Polar molecule

A molecule in which the overall charge is unevenly distributed because electrons spend more time near one atom than another, such as oxygen and hydrogen in water.

Cohesion

A phenomenon in which water molecules are held together by hydrogen bonds.

Adhesion

An attraction between different substances, for example, between water molecules and plant cell walls.

Surface tension

A measure of how hard it is to break the surface of a liquid.

Kinetic energy

The energy of motion.

Temperature

A measure of energy that represents the average kinetic energy of the molecules in a body of matter.

Thermal energy

The kinetic energy associated with the random motion of atoms or molecules.

Heat

Thermal energy transferred from one body of matter to another.

Calorie (cal)

The amount of heat required to raise the temperature of $1\,g$ of water by $1\,^\circ\text{C}$.

Specific heat

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

Evaporation

The transformation of a substance from liquid to gas.

Heat of vaporization

The heat a liquid must absorb for $1\,g$ to be converted to gas.

Evaporative cooling

The process in which, as a liquid evaporates, its remaining surface cools.

Solution

A liquid that is a completely homogeneous mixture of 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

The sphere of water molecules formed around each ion when a substance dissolves in water.

Hydrophilic substance

A substance that has an affinity for water.

Hydrophobic substance

A substance that does not have an affinity for water.

Molecular mass

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

Mole (mol)

A standard unit for measuring numbers of molecules, where $1\,\text{mole} = 6.02 \times 10^{23}$ molecules.

Molarity (M)

The number of moles of solute per liter of solution.

Hydronium ion

The molecule with an extra proton ($\text{H}_3\text{O}^+$), formed when a hydrogen atom in a hydrogen bond shifts from one water molecule to another.

Hydroxide ion

The molecule that lost a proton ($\text{OH}^-$) during a hydrogen ion transfer between water molecules.

Acid

Any substance that increases the $\text{H}^+$ concentration of a solution.

Base

Any substance that reduces the $\text{H}^+$ concentration of a solution.

pH

A measure defined by the negative logarithm of $\text{H}^+$ concentration, written as $\text{pH} = -\log[\text{H}^+]$.

Buffers

Substances that resist changes in concentrations of $\text{H}^+$ and $\text{OH}^-$ in a solution, maintaining its pH.