Topic 1: Structure of Water and Hydrogen Bonding

Vocabulary flashcards covering key terms related to the structure of water, bonding, and its properties as discussed in the lecture.

Matter

Anything that takes up space and has mass.

Element

A substance that cannot be broken down into other substances by chemical reactions.

Compound

A substance consisting of two or more different elements in a fixed ratio.

Essential elements

Approximately 20–25% of the 92 naturally occurring elements that are necessary to survive and reproduce.

CHOPN

Carbon, Hydrogen, Oxygen, Phosphorus, and Nitrogen; together make up about 96% of living matter.

Trace elements

Elements required by an organism in very small quantities.

Atomic number

The number of protons in an atom.

Atomic mass

The total number of protons and neutrons, averaged over all isotopes.

Groups

Vertical columns in the periodic table; elements in the same group have the same number of valence electrons.

Periods

Horizontal rows in the periodic table; elements in the same period have the same number of electron shells.

Valence electrons

Electrons in the outermost shell that participate in bonds.

Electron shells

Energy levels around the nucleus where electrons are found.

Electronegativity

An atom's ability to attract electrons; increases across a period and decreases down a group.

Covalent bond

A bond formed when two or more atoms share electrons; usually between nonmetals.

Nonpolar covalent bond

A covalent bond where electrons are shared equally between atoms.

Polar covalent bond

A covalent bond where electrons are shared unequally, creating partial charges (e.g., H–O in water).

Ionic bond

An attraction between oppositely charged ions, typically involving transfer of electrons from a metal to a nonmetal.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Hydrogen bond

A weak, intermolecular attraction between a partially positive H in one molecule and a partially negative atom (often O or N) in another.

Polarity

The existence of partial charges within a molecule due to unequal electron sharing in polar covalent bonds.

Cohesion

Attraction between water molecules, caused by hydrogen bonding.

Adhesion

Attraction of water to polar surfaces or other molecules.

Surface tension

Tensile strength at the surface of a liquid due to cohesive forces; water's surface is pulled inward by hydrogen bonds.

Capillary action

Upward movement of water driven by a combination of cohesion, adhesion, and surface tension.

Specific heat

Water's high ability to resist temperature changes, due to hydrogen bonding.

Heat of vaporization

The large amount of energy required to convert water from a liquid to a gas.

Evaporative cooling

Cooling that occurs when water evaporates, taking heat away from a surface (e.g., sweating).

Density of ice

Ice is less dense than liquid water, so ice floats; caused by the hydrogen-bonded crystal structure.

Solvent

The dissolving agent in a solution; water is a versatile solvent.

Solute

The substance dissolved in a solvent.

Solution

A homogeneous mixture of solute and solvent.

Like dissolves like

Polar solvents (like water) dissolve polar solutes and ionic compounds; nonpolar solvents dissolve nonpolar solutes.

pH

A measure of how acidic or basic (alkaline) a solution is.

Buffer

A solution that resists changes in pH when acids or bases are added.

Dissociation

Water can dissociate into hydrogen ions (H+) and hydroxide ions (OH−).

Hydrogen ion

A proton (H+) released by acids in water.

Hydroxide ion

OH−, a negatively charged ion formed when water dissociates.