Chapter 2: Matter and the Chemical Basis of Life

Vocabulary flashcards covering key concepts of chemistry, atomic structure, chemical bonding, water properties, and pH balance from Chapter 2.

Matter

Anything that takes up space and has mass.

Element

A substance that cannot be broken down to other substances by chemical reactions. There are $92$ naturally occurring elements.

Essential Elements

The $25$ chemical elements required for life, four of which—carbon (C), oxygen (O), hydrogen (H), and nitrogen (N)—make up $96\%$ of living matter.

Trace Elements

Elements required by an organism in minute quantities, which make up the remaining $4\%$ of living matter, such as iron (Fe), phosphorus (P), sulfur (S), calcium (Ca), and potassium (K).

Proton

A subatomic particle with a positive electric charge located in the atomic nucleus.

Neutron

A subatomic particle with a neutral electric charge located in the atomic nucleus.

Electron

A subatomic particle with a negative electric charge that orbits the atomic nucleus in energy levels.

Atomic Number

The specific number of protons contained in the nucleus of an atom.

Atomic Weight

The total number of protons plus neutrons in an atom.

Isotopes

Atoms of the same element that have the same number of protons but differ in their number of neutrons.

Radioactive Isotopes

Unstable isotopes that decay over time; used in medical diagnostic and treatment procedures as well as scientific research.

Valence Electrons

Electrons located in the outermost energy level (shell) of an atom that dictate its chemical behavior.

Compound

A substance consisting of two or more different elements chemically bonded together in a fixed ratio, such as $H_2O$.

Covalent Bond

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

Polar Covalent Bond

A covalent bond between atoms that differ in electronegativity, leading to unequal sharing of electrons and creating slightly positive and negative poles.

Nonpolar Covalent Bond

A covalent bond in which shared electrons are distributed equally between atoms, such as in methane.

Ionic Bond

A chemical bond resulting from the complete transfer of electrons from one atom to another, creating oppositely charged ions that attract each other.

Hydrogen Bond

A weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative atom in another molecule or another part of the same molecule.

Chemical Reactions

Processes that make and break chemical bonds to rearrange matter, converting reactants into products while conserving matter.

Cohesion

The tendency of water molecules to stick to each other through hydrogen bonding.

Adhesion

The attraction that causes water to stick to other substances.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, directly related to cohesive forces.

Evaporative Cooling

The reduction in temperature resulting from the evaporation of a liquid, which helps organisms regulate body temperature through sweating.

pH Scale

A measure of the acidity or alkalinity of a solution where each whole unit jump represents a tenfold difference in $H^+$ concentration.

Buffer

A solution that minimizes changes in pH by donating $H^+$ ions when in a basic environment and accepting $H^+$ ions when in an acidic environment.