Campbell Biology: Concepts & Connections - Chapter 2: The Chemical Basis of Life

Vocabulary practice flashcards covering key terms and concepts on elements, chemical bonds, water properties, and pH from Chapter 2 of Campbell Biology: Concepts & Connections.

Matter

Anything that occupies space and has mass; all living organisms are composed of it.

Element

A substance that cannot be broken down to other substances by ordinary chemical means; about 25 are essential for human life, and four make up about 96% of the weight of most living organisms.

Compound

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

Trace Elements

Elements that are essential for human life but are required in minute quantities (less than $0.01\%$ of body weight), often added to food or water to prevent disease.

Atom

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

Proton

A subatomic particle with a single positive electrical charge, packed with neutrons in the atom's nucleus.

Neutron

An electrically neutral subatomic particle, packed with protons inside an atom's nucleus.

Electron

A subatomic particle with a single negative electrical charge that orbits an atom's nucleus.

Nucleus (Atomic)

The central core of an atom where protons and neutrons are packed together.

Atomic Number

The unique number of protons found in the nucleus of an atom of a specific element.

Mass Number

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

Atomic Mass

The total mass of an atom, which is approximately equal to its mass number.

Isotopes

Atoms of the same element that have the identical number of protons but different numbers of neutrons.

Radioactive Isotope

An unstable isotope whose nucleus decays spontaneously, releasing particles and energy; widely used as tracers to monitor the fate of atoms in living organisms.

Electron Shell

An energy level of electrons at a characteristic distance from the nucleus of an atom.

Chemical Bonds

Attractions that hold atoms together, formed when atoms with incomplete outer shells interact to share, gain, or lose electrons.

Ionic Bond

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

Covalent Bond

A chemical bond in which two atoms do not transfer electrons but instead share one or more pairs of valence electrons.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

Polar Covalent Bond

A covalent bond where electrons are pulled closer to the more electronegative atom, resulting in unequal sharing and a separation of charges.

Ion

An atom or molecule with an electrical charge resulting from the gain or loss of one or more electrons.

Salt

A synonym for an ionic compound, such as sodium chloride ($\text{NaCl}$).

Hydrogen Bond

A weak type of chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to a slightly negative atom of a polar covalent bond in another molecule.

Polar Molecule

A molecule, such as water ($\text{H}_2\text{O}$), that has an unequal distribution of charges due to its polar bonds and shape.

Chemical Reaction

A process that breaks existing chemical bonds and forms new ones, converting reactants into products without creating or destroying matter.

Reactants

The starting materials that undergo conversion in a chemical reaction.

Products

The ending materials resulting from a chemical reaction.

Cohesion

The tendency of molecules of the same kind to stick together, mediated in water by hydrogen bonding.

Adhesion

The clinging of one substance to another, such as water molecules sticking to plant cell walls.

Surface Tension

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

Thermal Energy

The kinetic energy associated with the random movement of atoms and molecules.

Heat

Thermal energy in transfer from a warmer body of matter to a cooler body of matter.

Temperature

A measure of the intensity of heat, reflecting the average speed or kinetic energy of molecules in a body of matter.

Evaporative Cooling

The process in which the surface of a liquid that remains behind cools down as the liquid evaporates.

Solution

A liquid consisting of a uniform, homogeneous mixture of two or more substances.

Solvent

The dissolving agent in a solution.

Solute

A substance that is dissolved in a solvent to create a solution.

Aqueous Solution

A solution in which water acts as the solvent.

pH Scale

A scale ranging from $0$ to $14$ used to describe how acidic or basic a solution is based on relative concentrations of $\text{H}^+$ and $\text{OH}^-$.

Buffer

A substance that minimizes changes in pH by accepting $\text{H}^+$ when it is in excess and donating $\text{H}^+$ when it is depleted.

Ocean Acidification

The process by which dissolved atmospheric $\text{CO}_2$ reacts with seawater to form an acid, lowering ocean pH and reducing carbonate ion ($\text{CO}_3^{2-}$) concentrations required for coral calcification.