Chapter 2 - Summary: Atoms, Water, and Carbon in Biology, Key Terms from Chapter 2 of Biology 2e, The Chemical Foundation of Life in Biology

Matter

Anything that occupies space and has mass.

Elements

Substances that cannot be broken down chemically.

Atoms

Smallest units retaining properties of an element.

Protons

Positively charged particles in an atom's nucleus.

Neutrons

Neutral particles in an atom's nucleus.

Electrons

Negatively charged particles orbiting an atom's nucleus.

Ionic Bonds

Bonds formed by electron transfer between atoms.

Covalent Bonds

Bonds formed by sharing electrons between atoms.

Hydrogen Bonds

Weak bonds between polar molecules due to charge.

Van der Waals Interactions

Weak attractions between molecules or parts of molecules.

Polar Molecule

Molecule with uneven distribution of charge.

Solvent

Substance that dissolves solutes, forming a solution.

Heat Capacity

Amount of heat needed to change temperature.

Heat of Vaporization

Energy required for a substance to vaporize.

Cohesion

Attraction between molecules of the same substance.

Surface Tension

Tendency of liquid surfaces to shrink.

Adhesion

Attraction between different substances or molecules.

pH Value

Measure of hydrogen ion concentration in a solution.

Buffers

Substances that moderate pH changes in solutions.

Carbon

Element central to biological molecules and life.

Hydrocarbon Chains

Long chains of carbon and hydrogen atoms.

Functional Groups

Groups of atoms that confer specific chemical properties.

acid

molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution

adhesion

attraction between water molecules and other molecules

aliphatic hydrocarbon

hydrocarbon consisting of a linear chain of carbon atoms

anion

negative ion that is formed by an atom gaining one or more electrons

aromatic hydrocarbon

hydrocarbon consisting of closed rings of carbon atoms

atom

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

atomic mass

calculated mean of the mass number for an element's isotopes

atomic number

total number of protons in an atom

balanced chemical equation

statement of a chemical reaction with the number of each type of atom equalized for both the products and reactants

base

molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the hydrogen ions' concentration in a solution

buffer

substance that resists a change in pH by absorbing or releasing hydrogen or hydroxide ions

calorie

amount of heat required to change the temperature of one gram of water by one degree Celsius

capillary action

occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the tubes' sides

cation

positive ion that is formed by an atom losing one or more electrons

chemical bond

interaction between two or more of the same or different atoms that results in forming molecules

chemical reaction

process leading to rearranging atoms in molecules

chemical reactivity

the ability to combine and to chemically bond with each other

cohesion

intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension

compound

substance composed of molecules consisting of atoms of at least two different elements

covalent bond

type of strong bond formed between two atoms of the same or different elements; forms when electrons are shared between atoms

dissociation

release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H and OH

electrolyte

ion necessary for nerve impulse conduction, muscle contractions, and water balance

electron

negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of -1 unit

electron configuration

arrangement of electrons in an atom's electron shell (for example, 1s 2s 2p)

electron orbital

how electrons are spatially distributed surrounding the nucleus; the area where we are most likely to find an electron

electron transfer

movement of electrons from one element to another; important in creating ionic bonds

electronegativity

ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms

element

one of 118 unique substances that cannot break down into smaller substances; each element has unique properties and a specified number of protons

enantiomers

molecules that share overall structure and bonding patterns, but differ in how the atoms are three dimensionally placed such that they are mirror images of each other

equilibrium

steady state of relative reactant and product concentration in reversible chemical reactions in a closed system

evaporation

change from liquid to gaseous state at a body of water's surface, plant leaves, or an organism's skin

functional group

group of atoms that provides or imparts a specific function to a carbon skeleton

geometric isomer

isomer with similar bonding patterns differing in the placement of atoms alongside a double covalent bond

heat of vaporization of water

high amount of energy required for liquid water to turn into water vapor

hydrocarbon

molecule that consists of

amount of energy required for liquid water to turn into water vapor

The energy needed for water to transition from a liquid state to a gaseous state.

hydrocarbon

Molecule that consists only of carbon and hydrogen.

hydrogen bond

Weak bond between slightly positively charged hydrogen atoms and slightly negatively charged atoms in other molecules.

hydrophilic

Describes ions or polar molecules that interact well with other polar molecules such as water.

hydrophobic

Describes uncharged nonpolar molecules that do not interact well with polar molecules such as water.

inert gas (also, noble gas)

Element with filled outer electron shell that is unreactive with other atoms.

ion

Atom or chemical group that does not contain equal numbers of protons and electrons.

ionic bond

Chemical bond that forms between ions with opposite charges (cations and anions).

irreversible chemical reaction

Chemical reaction where reactants proceed unidirectionally to form products.

isomers

Molecules that differ from one another even though they share the same chemical formula.

isotope

One or more forms of an element that have different numbers of neutrons.

law of mass action

Chemical law stating that the rate of a reaction is proportional to the concentration of the reacting substances.

litmus paper (also, pH paper)

Filter paper treated with a natural water-soluble dye that changes its color as the pH of the environment changes in order to use it as a pH indicator.

mass number

Total number of protons and neutrons in an atom.

matter

Anything that has mass and occupies space.

molecule

Two or more atoms chemically bonded together.

neutron

Uncharged particle that resides in an atom's nucleus; has a mass of one amu.

noble gas

See inert gas.

nonpolar covalent bond

Type of covalent bond that forms between atoms when electrons are shared equally between them.

nucleus

Core of an atom; contains protons and neutrons.

octet rule

Rule that atoms are most stable when they hold eight electrons in their outermost shells.

orbital

Region surrounding the nucleus; contains electron(s).

organic molecule

Any molecule containing carbon (except carbon dioxide).

periodic table

Organizational chart of elements indicating each element's atomic number and atomic mass; provides key information about the elements' properties.

pH paper

See litmus paper.

pH scale

Scale ranging from zero to 14 that is inversely proportional to the hydrogen ions' concentration in a solution.

polar covalent bond

Type of covalent bond that forms as a result of unequal electron sharing, resulting in creating slightly positive and negative charged molecule regions.

product

Molecule that is the result of a chemical reaction.

proton

Positively charged particle that resides in the atom's nucleus; has a mass of one amu and a charge of +1.

radioisotope

Isotope that emits radiation comprised of subatomic particles to form more stable elements.

reactant

Molecule that takes part in a chemical reaction.

reversible chemical reaction

Chemical reaction that functions bidirectionally, where products may turn into reactants if their concentration is great enough.

solvent

Substance capable of dissolving another substance.

specific heat capacity

The amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius.

sphere of hydration

When a polar water molecule surrounds charged or polar molecules thus keeping them dissolved and in solution.

structural isomers

Molecules that share a chemical formula but differ in the placement of their chemical bonds.

substituted hydrocarbon

Hydrocarbon chain or ring containing an atom of another element in place of one of the backbone carbons.

surface tension

Tension at the surface of a body of liquid that prevents the molecules from separating; created by the attractive cohesive forces between the liquid's molecules.

valence shell

Outermost shell of an atom.

van der Waals interaction

Very weak interaction between molecules due to temporary charges attracting atoms that are very close together.

Matter

Occupies space and has mass.

Elements

Unique forms of matter with specific properties.

Chemical Symbol

One or two letters representing an element.