The first course in the 75/76 sequence has specific prerequisite courses that are given in the course descriptions elsewhere in this web site. These prerequisites have been carefully chosen to provide the mathematical and chemical background that will be used throughout all physical chemistry courses, and if you have not taken them, you must discuss your background with the course instructor in order to secure her or his permission to enroll.
Your satisfaction with physical chemistry will depend on more than your background, however. Physical chemistry is the most mathematical branch of chemistry (indeed all of theoretical chemistry is a very large subset of physical chemistry), and while the mathematics needed in any of these courses is neither impossibly difficult nor beyond the level of the prerequisite math courses, a good understanding of physical chemistry requires more than an ability to manipulate mathematical expressions. In particular, keep the following in mind:
1. Equations have physical meaning. The goal of physical chemistry is a quantitative description of chemical and physical phenomena. Every variable in every equation has a physical meaning, and the mathematical relationship among such variables implies a physical consequence. For instance, the simple ideal gas equation of state, PV = nRT, contains four physical variables: the gas equilibrium pressure P, its volume V, its amount n, and its absolute temperature T. There is one universal physical constant, the gas constant R. The equation itself expresses several physical phenomena, such as: hold the volume and the amount of gas constant and the pressure increases in direct proportion to the absolute temperature. The ability to "read" equations and give them a physical interpretation such as this is key to understanding physical chemistry.
2. Temperature Scales. Be familiar with the Celsius (Centigrade) and the Kelvin (absolute) temperature scales. Lab thermometers are most often graduated in Celsius degrees, but most equations (essentially all theoretical expressions) require you to express temperature in Kelvin. And note that the unit symbol for Kelvin is simply K rather than °K whereas the Celsius unit symbol always carries the degree symbol: °C.
3. SI Units. Familiarize yourself with the most common basic SI units of physical chemistry: length (in meters, m), time (in seconds, s), mass (in kilograms, kg), and amount of something (in moles, mol). Electric charge is not a fundamental SI quantity; rather, electric current (in amperes, A, where 1 A = 1 C/s, or one coulomb, C, of charge moving past any point per second) is fundamental. Likewise, review the relationship among the fundamental quantities and the so-called derived physical quantities such as velocity, energy, etc. For example, the common SI unit for energy is the joule, J, where 1 J = 1 kg m2/s2. Familiarity with these unit decompositions allow you to take a complicated expression involving perhaps many derived physical quantity units and reduce them via simple unit algebra into their final representation (which may often be expressed more simply in terms of familiar derived quantities).
4. Always, always, ALWAYS write the units associated with every physical quantity. This is very important. If you are expecting your calculation to lead to a physical quantity, you must ensure that your final result has the correct units for that quantity. If it doesn't, then you have made a mistake somewhere, either in the units you assigned to the input quantities or in the expression itself or in the way you reduced units leading from the input quantities to the final answer.
5. Check your answer for numerical sensibility. This rule requires some experience and practice because you may not know what is a sensible answer your first time through a new physical situation. With practice, however, you will gain more confidence. For example, if you are asked to calculate the distance between two bonded atoms in a molecule, you should expect your answer to be on the order of a few Ångström units (1 Å = 10–10 m) in magnitude. If your answer is many orders of magnitude different, it is likely you made a unit error somewhere or a simple mathematical mistake.
If you keep these rules in mind and continue to practice them and review your practice, you will build a strong foundation for understanding and appreciating physical chemistry.
Good luck, and don't forget to ask your instructor for help whenever you need it!
