Cecil Dybowski




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GENERAL TIPS ON SOLVING PROBLEMS

IN PHYSICAL CHEMISTRY


Cecil Dybowski


Department of Chemistry and Biochemistry

University of Delaware

Newark, Delaware 19716-2522

  • Understanding concepts is the key to working problems. Read the book carefully and try to understand the relationships between various physical properties.




  • When working a problem, read the statement of the problem at least twice. This gives you an opportunity to focus on what is given and what is not. The second and subsequent readings also refocus on the specifics that may have been missed on first reading. Many people find that, at first glance, they have misinterpreted what is asked.




  • Look carefully at data presented. Ask yourself what is given and how this relates to what you need to answer the question asked. These are not usually the same.




  • In setting up the solution to a problem, do not just seek an equation containing all the parameters listed in a problem, into which you can “plug the numbers in”. Equations do not apply to all situations. A critical part of learning is understanding the limitations on the use of equations. After all, you would not use a sledge hammer to put a small nail into your wall to hang a piciture.




  • When tables of real data are given, you must consider the appropriate method for analyzing real data, taking into consideration noise. (After all, this is not an ideal world.) A particularly egregious error, for example, is using a two-point formula to determine a straight line’s slope from just two data points. This procedure neglects all the information contained in other data and accentuates the contributions from noise in those two points. It often leads, unless very high-quality data are available, to erroneous or misleading results.




  • Graphs help you “see” data. Use plots of one variable against another to give you a visual impression of the way they are related.







  • Know the common units of various physical quantities. For example, the appropriate unit for energy is the joule. While this is equivalent to a kg m2 sec-2, the former is a unit of energy; the latter is a conglomeration of fundamental units.




  • In some cases, special units are defined for quantities that arise in certain experiments; know them and when to use them. For example, the sedimentation coefficient has units of time, but the appropriate unit in which to present the answer is the svedberg, not the second.




  • Computers and calculators are robotic tools. They are only as useful as the creativity of the person using them permits. Be sure you understand what a tool does before you use it to solve problems. Only in that way will the solution it generates be meaningful.



TIPS ON TAKING EXAMS AND QUIZZES





  • A quiz or examination is a device for the examinee to communicate his/her knowledge to the examiner. It is important that one always keep in mind this aspect of an examination Things that are not communicated clearly may be misunderstood.




  • Be neat! Remember to show the examiner that you are in control of the situation. A sloppy paper communicates a state of disorganization of the examinee’s knowledge. Write in pencil so you can erase if mistakes are made.




  • Be concise. A well-answered question has a kind of brevity that says everything that needs to be said, but in a compact way.




  • Take time to read over all questions before beginning to work on any one. This gives a reconnaissance of the exam.







  • Do not answer questions not asked. It wastes your time, and does not gain you much recognition for having knowledge.




  • When answering a question, start the answer at the top of the answer space and write successively down the space. Do not write things randomly in the answer space. There are two reasons for this: (1) such random writing is evidence of the disorganization discussed above; (2) such writing makes it difficult for the grader to follow the line of reasoning and may result in misunderstanding of the idea being expressed.



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