Chapter 2: The Chemical Level of Organization

Vocabulary practice cards for Chapter 2 covering basic chemistry, subatomic particles, atomic structure, chemical bonds, reactions, enzymes, water properties, and acid-base chemistry.

Chemistry

The science that deals with the structure and properties of matter.

Matter

Anything that takes up space and has mass.

Mass

The amount of material in matter.

Atom

The smallest stable unit of matter.

Proton

A subatomic particle carrying a positive charge and consisting of 1 mass unit.

Neutron

A subatomic particle carrying a neutral charge and consisting of 1 mass unit.

Electron

A subatomic particle carrying a negative charge with a comparably very low mass.

Nucleus (Atomic)

The central region of an atom that contains protons and neutrons.

Electron Cloud

The area around the nucleus of an atom that contains electrons.

Element

A pure substance composed of atoms of only one kind.

Atomic Number

The specific number of protons in an element's nucleus.

Mass Number

The total number of protons plus the number of neutrons in an atom.

Isotopes

Atoms of the same element containing the same number of protons but differing in the number of neutrons and mass number.

Radioisotopes

Isotopes with unstable nuclei that emit radiation as they decay to a more stable form.

Half-life

The amount of time required for half of a given amount of a radioisotope to decay.

Atomic Weight

The average of the atomic masses and proportions of an element's different isotopes.

Mole

A unit of measurement (mol) of an element having a weight in grams equal to its atomic weight.

Valence Shell

The outermost electron shell of an atom, where the number of electrons determines the element's chemical properties and reactivity.

Molecule

A chemical structure consisting of two or more atoms joined together by strong bonds.

Compound

A substance composed of two or more atoms of different elements joined by strong or weak bonds.

Molecular Weight

The sum of the atomic weights of all the atoms in a molecule or compound.

Cation

A positively charged ion formed when an atom loses one or more electrons.

Anion

A negatively charged ion formed when an atom gains one or more electrons.

Ionic Bond

A chemical bond formed by the electrical attraction between oppositely charged cations and anions.

Covalent Bond

A strong chemical bond created when atoms share electrons.

Nonpolar Covalent Bond

A covalent bond involving equal sharing of electrons between atoms with equal pull.

Polar Covalent Bond

A covalent bond involving unequal sharing of electrons because one atom exerts a stronger pull on electrons.

Hydrogen Bond

A weak electrical attraction between the partial positive charge of a hydrogen atom in a polar covalent bond and the partial negative charge of another atom.

Metabolism

All chemical reactions occurring in the cells and tissues of the human body at any given time.

Work

The movement of an object or a change in the physical structure of matter.

Energy

The capacity to do work.

Kinetic Energy

The energy of motion.

Potential Energy

Stored energy capable of doing work.

Chemical Energy

Potential energy stored in chemical bonds that can be converted to kinetic energy.

Decomposition Reaction

A chemical reaction (catabolism) that breaks chemical bonds and releases energy.

Hydrolysis Reaction

A decomposition reaction involving the breakdown of a molecule with water.

Synthesis Reaction

A chemical reaction (anabolism) that forms chemical bonds by assembling larger molecules from smaller ones.

Dehydration Synthesis

A synthesis reaction (condensation) that combines molecules while producing water.

Exchange Reaction

A chemical reaction in which components of reactants are rearranged to form new products.

Reversible Reaction

A reaction that seeks equilibrium, where opposing forward and reverse reaction rates balance out.

Activation Energy

The amount of energy required to start a chemical reaction.

Enzymes

Protein catalysts that lower activation energy to speed up chemical reactions without being consumed.

Exergonic Reaction

A chemical reaction that releases energy because the energy released exceeds the activation energy.

Endergonic Reaction

A chemical reaction that absorbs energy because the activation energy is greater than the energy produced.

Nutrients

Substances from food necessary for physiological function in the body.

Metabolites

Substances synthesized or broken down by chemical reactions involved in metabolism.

Inorganic Molecules

Molecules that are not based on carbon and hydrogen, such as carbon dioxide, oxygen, water, inorganic acids, and salts.

Organic Molecules

Molecules based on carbon, hydrogen, and usually oxygen, held together primarily by covalent bonds.

High Heat Capacity

The property of water requiring a large amount of heat to raise the temperature of 1 gram of water by $1^\text{o}\text{C}$.

Solution

A uniform liquid mixture consisting of a solvent and dissolved solutes.

Aqueous Solution

A solution in which water serves as the solvent.

Dissociation

The splitting of inorganic compounds into smaller molecules or ions in water.

Ionization

The dissociation of a substance in solution into electrical charged ions.

Hydration Spheres

Structures formed by polar water molecules surrounding ions or small polar molecules to keep them in solution.

Electrolytes

Inorganic ions that conduct electricity in body fluid solutions.

Hydrophilic

Molecules, such as ions and polar molecules, that readily interact with water.

Hydrophobic

Nonpolar molecules, fats, and oils that do not interact with water and are repelled by it.

Colloid

A solution containing dispersed proteins or other large molecules, such as blood plasma and milk.

Suspension

A mixture containing large particles that settle out of solution, such as whole blood containing blood cells.

pH

The negative logarithm of the hydrogen ion concentration of a solution in moles per liter.

Acid

A solute functioning as a proton donor that adds hydrogen ions ($\text{H}^+$) to a solution.

Base

A solute functioning as a proton acceptor that removes hydrogen ions ($\text{H}^+$) from a solution.

Salt

A solute that dissociates into cations and anions other than hydrogen ions ($\text{H}^+$) and hydroxide ions ($\text{OH}^-$).

Buffer

A compound that stabilizes solution pH by donating or absorbing hydrogen ions.