Hess's Law: The enthalpy change for a change is the same whether it takes place in one big step or in many small ones. heterogeneous mixture: A mixture where the substances aren't equally distributed. homogeneous mixture: A mixture that looks really "smooth" because everything is mixed up really well. Hund's rule: The most stable arrangement of electrons occurs when they're all unpaired. hybrid orbital: An orbital caused by the mixing of s, p, d, and f-orbitals. hydration: When a molecule has water molecules attached to it. hydrocarbon: A molecule containing carbon and hydrogen. hydrogen bond: The tendency of the hydrogen atom stuck to an electronegative atom to become attracted to the lone pair electrons on another electronegative atom. It's a pretty strong intermolecular force, which explains why water has such a high melting and boiling point.

hydronium ion: The H+ ion, made famous by acids. hydroxide ion: The OHion, made famous by bases. ideal gas law: PV=nRT ideal gas: A gas in which the particles are infinitely small, have a kinetic energy directly proportional to the temperature, travel in random straight lines, and don't attract or repel each other. Needless to say, there's no such thing as an ideal gas in the real world. However, we use ideal gases anyway because they make the math work out well for equations that describe how gases behave. ideal solution: A solution in which the vapor pressure is directly proportional to the mole fraction of solvent present immiscible: When two substances don't dissolve in each other. Think of oil and water. They're immiscible. Organic compounds and water are frequently immiscible. indicator: A compound that turns different colors at different pH values. We generally like to have the color change at a pH of

s where the equivalence point of a titration is. inhibitor: A substance that slows down a chemical reaction. inorganic compound: Any compound that doesn't contain carbon (except for carbon dioxide, carbon monoxide, and carbonates). insoluble: When something doesn't dissolve. intermediate: A molecule which exists for a short time in a chemical reaction before turning into the product. intermolecular force: A force that exists between two different molecules. Examples are hydrogen bonding (which is strong), dipole-dipole forces (which are kind of weak), and London dispersion forces (a.k.a. Van der Waal forces), which are very weak. ionic bond: A bond formed when charge particles stick together. ionization energy: The amount of energy required to pull an electron off of a gaseous atom. irreversible reaction: A chemical reaction in which the reagents make products but the products can't reform reagents. Most chemical reactions in basic chemistry classes are though

isotonic solutions: Solutions containing the same osmotic pressure. isotope: When an element has more than one possibility for the number of neutrons, these are called isotopes. All known elements possess isotopes. For the record, the word "isotope" doesn't imply that something is radioactive. TV told you that, and TV is stupid.