Biology 2e Chapter 2: The Chemical Foundation of Life

Flashcards covering the chemical foundation of life, including atomic structure, chemical bonding, properties of water, and pH.

Matter

Anything that occupies space and has mass.

Elements

Unique forms of matter with specific chemical and physical properties that cannot be broken down into smaller substances.

Most Common Elements in Living Organisms

Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N).

Atom

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

Nucleus

The center of the atom which contains protons and neutrons.

Proton

A sub-atomic particle located in the nucleus with a charge of $+1$ and a mass of $1\,\text{amu}$.

Neutron

A sub-atomic particle located in the nucleus with a charge of $0$ and a mass of $1\,\text{amu}$.

Electron

A sub-atomic particle located in orbitals with a charge of $-1$ and a mass of $0\,\text{amu}$.

Atomic Number

The number of protons in an atom, which is distinct for each element.

Atomic Mass

The mass of the atom, roughly equal to the number of protons and neutrons, expressed in atomic mass units ($\text{amu}$).

Isotopes

Forms of an element with different numbers of neutrons and thus different mass numbers.

Bohr Model

An early atomic model where protons are in the nucleus and electrons are in circular orbits at specific distances called electron shells or energy levels.

Valence Shell

The outermost electron shell of an atom.

Octet Rule

The principle that the most stable configuration for the first two outer shells of an atom occurs when they each have eight electrons.

Reactants

Substances used at the beginning of a chemical reaction.

Products

Substances formed at the end of a chemical reaction.

Irreversible Reaction

A chemical reaction that proceeds in one direction until all the reactants are used up.

Reversible Reaction

A chemical reaction where reactants are converted to products, but some product can be converted back to reactant.

Chemical Bond

The attractive force that links atoms together to form molecules.

Covalent Bond

A strong bond formed when two or more atoms share electrons to become more stable.

Ionic Bond

A strong bond formed by an attraction between two oppositely charged ions, typically where metals lose electrons and nonmetals gain electrons.

Polar Covalent Bond

A bond where electrons are unequally shared and attracted more to one nucleus than the other, such as the bonds in a water molecule ($H_2O$).

Non-Polar Covalent Bond

A bond where electrons are shared equally by the atoms, such as in Methane ($CH_4$).

Hydrogen Bond

A weak attraction between the slightly positively charged hydrogen atom ($\delta+$) of one molecule and the slightly negatively charged atom ($\delta-$) of another molecule.

Specific Heat Capacity

The amount of heat one gram ($1\,\text{g}$) of a substance must absorb in order to raise its temperature one degree Celsius ($1\,^{\circ}\text{C}$).

Heat of Vaporization

The amount of energy required to change one gram ($1\,\text{g}$) of a liquid substance to a gas.

Solvent

A substance (like water) capable of dissolving other polar molecules and ions.

Solute

The compounds dissolved or mixed in with a solvent.

Dissociation

The process where atoms break off from molecules and form ions, such as $NaCl$ breaking into ions in water.

Cohesion

The property of water molecules at the liquid-gas interface sticking together due to hydrogen bonding.

Surface Tension

The capacity of a substance to withstand being ruptured when placed under tension or stress.

Adhesion

An attraction between water molecules and other molecules.

Capillary Action

The phenomenon where water moves up a glass tube because the adhesive forces to the glass exceed the cohesive forces between water molecules.

pH

A measure indicating the acidity or alkalinity of a solution, defined as the negative of the base 10 logarithm of the hydrogen ion concentration ($[H^+]$).

Acidic Solutions

Solutions with a high $H^+$ concentration and a \text{pH} < 7.

Alkaline (Basic) Solutions

Solutions with a high $OH^-$ concentration and a \text{pH} > 7.

Hydrocarbons

Molecules consisting of carbon and hydrogen, such as Methane ($CH_4$), which store energy in their covalent bonds.