Chapter 2 AI Notes for Test

Element

A pure substance that cannot be broken down chemically, consisting entirely of one type of atom.

Atom

The smallest unit of matter that retains all the chemical properties of an element.

Compound

A substance composed of two or more different chemical elements held together in fixed ratios by chemical bonds.

Four primary elements of living matter

Carbon, hydrogen, oxygen, and nitrogen.

Trace element

A chemical element required by an organism in minute quantities for normal growth and physiological function.

Atomic number

The quantity of protons located within the nucleus of an atom.

Mass number

The sum of the protons and neutrons present in an atom's nucleus.

Isotope

An atomic form of an element that possesses the identical number of protons but a differing number of neutrons.

Ion

An atom or group of bonded atoms that has acquired an electrical charge by gaining or losing one or more electrons.

Covalent bond

A chemical connection formed when two atoms share one or more pairs of valence electrons.

Polar covalent bond

A bond where electrons are pulled closer to the more electronegative atom, resulting in unequal sharing and partial electric charges.

Nonpolar covalent bond

A bond where electrons are shared equally between two atoms with similar electronegativities.

Ionic bond

A chemical attraction between two oppositely charged ions resulting from the complete transfer of electrons.

Hydrogen bond

A weak noncovalent attraction between a partially positive hydrogen atom and an electronegative atom of another molecule.

Reactants

The initial starting materials that are consumed or altered during the course of a chemical reaction.

Products

The newly configured substances formed as the end result of a chemical reaction.

Cohesion in water

The attraction of water molecules to one another through hydrogen bonds, facilitating fluid transport and surface tension.

Temperature moderation by water

The property that allows large bodies of water to absorb or release substantial thermal energy with relatively small changes in temperature.

Reason ice floats on liquid water

Hydrogen bonds fix water molecules in a spacious, crystalline lattice at freezing temperatures, lowering solid water density.

Water's solvent capacity

The property where water's polarity enables it to surround, separate, and dissolve polar molecules and ionic compounds.

Acid

A substance that increases the concentration of hydrogen ions ($H^+$) in an aqueous solution.

Base

A substance that reduces the concentration of hydrogen ions ($H^+$) in a solution, often by accepting them.

pH scale

A numerical scale where values below $7$ are acidic, $7$ is neutral, and values above $7$ are basic, each unit signifying a tenfold change in $H^+$ concentration.

Buffer

A substance that moderates and resists sharp shifts in pH by accepting or donating hydrogen ions.