Structure of Water and Hydrogen Bonding Review

Vocabulary flashcards covering basic chemistry concepts, chemical bonding types, and the unique properties of water based on the lecture transcript.

Matter

Anything that takes up space and has mass, including rocks, metals, oils, gases, and organisms.

Element

A substance that cannot be broken down into other substances by chemical reactions; 92 of these occur in nature.

Compound

A substance consisting of two or more different elements combined in a fixed ratio, such as $H_2O$ or $NaCl$.

Essential elements

The $20-25\%$ of natural elements required to survive and reproduce; CHOPN (Carbon, Hydrogen, Oxygen, Phosphorus, and Nitrogen) make up $96\%$ of living matter.

Trace elements

Elements required by an organism in very small quantities.

Atomic number

The number of protons in an element.

Atomic mass

The number of protons plus neutrons averaged over all isotopes.

Octet rule

The principle that elements will gain, lose, or share electrons to complete their valence shell and become stable like noble gases.

Valence shell

The outermost layer of electrons in an atom.

Chemical Bonds

An attraction between two atoms resulting from the sharing or transferring of valence electrons.

Electronegativity

The measure of an atom's ability to attract electrons to itself.

Covalent bonds

Bonds formed when two or more atoms share electrons, typically between two nonmetals.

Nonpolar covalent bond

A type of covalent bond where electrons are shared equally between two atoms, such as in $O_2$.

Polar covalent bond

A type of covalent bond where electrons are not shared equally, resulting in partial charges on the atoms, such as in $H_2O$.

Ionic bonds

The attraction between oppositely charged atoms (ions) occurring when there is a transfer of electrons from one atom to another, usually between a metal and nonmetal.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Hydrogen bond

An intermolecular bond where the partially positive hydrogen atom in one polar covalent molecule is attracted to an electronegative atom in another polar covalent molecule.

Cohesion

The attraction of molecules for other molecules of the same kind; in water, hydrogen bonds hold $H_2O$ molecules together.

Surface tension

A property resulting from cohesion where surface water molecules experience a greater inward pull, allowing water to resist external force.

Adhesion

The attraction of water molecules to other molecules that are polar or have a charge, such as sticking to xylem walls in plants.

Capillary Action

The upward movement of water due to the forces of cohesion, adhesion, and surface tension; occurs when adhesion is greater than cohesion.

High Specific Heat

Water's resistance to temperature changes because heat must be absorbed to break hydrogen bonds and is released when they form.

High heat of vaporization

The large amount of energy required for water to evaporate due to strong hydrogen bonds.

Evaporative cooling

A process where the surface gets cooler as water molecules evaporate, helping to stabilize temperatures in organisms and environments.

Solution

A homogenous mixture consisting of two or more substances.

Solvent

The dissolving agent in a solution; water is a versatile example due to its polarity.

Solute

The substance that is dissolved in a solution.

pH

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

Acid

A substance that releases hydrogen ions ($H^+$) when dissolved in water.

Base

A substance that accepts $H^+$ or releases hydroxide ions ($OH^-$) when dissolved in water.

Buffer

A solution that resists changes in pH when an acid or base is added, helping maintain stability in biological systems.