Structure of Water and Hydrogen Bonding - Chemistry Review (Getting Down with Science 2020)

Vocabulary flashcards covering key concepts from the notes on matter, elements, bonding, and properties of water.

Matter

Anything that takes up space and has mass (e.g., rocks, metals, oils, gases, organisms).

Element

A substance that cannot be broken down into other substances by chemical reactions; one of the 92 naturally occurring elements.

Compound

A substance made of two or more different elements in a fixed ratio (e.g., H2O, NaCl).

Periodic table

A chart organizing elements by atomic number and chemical properties.

H2O

Water; a polar molecule essential for life and a common solvent.

NaCl

Sodium chloride; common table salt; an example of an ionic compound.

CHOPN

Essential elements: Carbon, Hydrogen, Oxygen, Phosphorus, Nitrogen; make up about 96% of living matter.

Essential elements

Elements required by organisms to survive and reproduce (about 20–25% of natural elements).

Trace elements

Elements required in very small quantities by organisms.

Atomic number

The number of protons in an atom’s nucleus.

Element symbol

The one- or two-letter abbreviation for an element (e.g., H, He, C).

Atomic mass

The average mass of an element’s atoms, roughly protons plus neutrons, averaged over isotopes.

Valence electrons

Electrons in the outermost shell that participate in bonding.

Electron shells

Energy levels around the nucleus that house electrons; same number of shells in a row indicates similar electron arrangement.

Octet rule

Atoms gain, lose, or share electrons to complete their valence shell to eight electrons.

Electronegativity

A measure of an atom’s ability to attract electrons in a bond.

Covalent bond

A bond formed by sharing electrons, usually between nonmetals.

Nonpolar covalent bond

A covalent bond where electrons are shared equally, no partial charges (e.g., O2).

Polar covalent bond

A covalent bond with unequal sharing of electrons, producing partial charges (e.g., H2O).

Ionic bond

Bond between oppositely charged ions formed by transfer of electrons (often metal to nonmetal).

Cation

Positively charged ion formed when an atom loses electrons.

Anion

Negatively charged ion formed when an atom gains electrons.

Hydrogen bond

A weak, intermolecular bond where a partially positive hydrogen in one molecule attracts a electronegative atom in another.

Polar molecule

Molecule with partial charges due to unequal electron sharing (e.g., water).

Cohesion

Attraction between like molecules (water–water) due to hydrogen bonding; enables transport in plants and surface tension.

Adhesion

Attraction of water to polar or charged surfaces (e.g., xylem walls).

Capillary action

Upward movement of water due to cohesion, adhesion, and surface tension; occurs when adhesion exceeds cohesion.

Surface tension

Tensional force at the surface of a liquid due to cohesive forces.

High specific heat

Water resists temperature changes because hydrogen bonds absorb/release heat.

High heat of vaporization

Large energy required to vaporize water; enables evaporative cooling.

Evaporative cooling

Cooling effect when water evaporates from a surface.

Density

Mass per volume; ice is less dense than liquid water, causing ice to float.

Solvent

Substance that dissolves solutes; water is a versatile polar solvent.

Solute

Substance dissolved in a solvent.

Solution

A homogeneous mixture of two or more substances.

Like dissolves like

Polar solvents dissolve polar solutes; nonpolar solvents dissolve nonpolar solutes.

Hydration shell

Shell of water molecules surrounding a dissolved ion or molecule.

Hydration

Process of water molecules surrounding and interacting with dissolved substances.

pH

A scale measuring how acidic or basic (alkaline) a solution is.

Acid

Substance that releases H+ ions in water.

Base

Substance that accepts H+ or releases OH− ions in water.

Buffer

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

Autoionization of water

Water dissociates into H+ and OH− ions (Kw dependent on temperature).

Ionic compound

Compound held together by ionic bonds (often metal and nonmetal), e.g., NaCl, LiF.

Xylem

Plant tissue that transports water; relies on cohesion, adhesion, and capillary action.

Transpiration

Loss of water vapor from plant surfaces driving water movement through the plant.

Molecule

Two or more atoms bonded together.

Ion

Atom or molecule with a net electric charge due to gain or loss of electrons.