The term paper is an opportunity for you to explore some topic of interest in considerable depth but is also designed to give you the opportunity to integrate material from throughout the course. In that regard some topics are bound to be more appropriate than others. "The causes of war throughout history (or even in the 20th century)" is much too broad. Conversely, while something along the lines of "The role of serotonin in regulating aggressive behavior" might well fill several pages it is probably too narrow to incorporate much material from the course. In selecting a topic there are also issues of whether you can get easy access to source materials and whether you have sufficient background to comprehend them in enough detail for them to be useful.
For these reasons it is important that you settle on a topic early and begin your investigations of relevant materials as soon as possible. It is not absolutely necessary that I approve the topic, but I can be helpful in guiding and shaping. Therefore I urge you to keep me posted on your efforts.
Students always want to know how long such papers should be, and the only legitimate answer is "as long as they need to be". My sense is that if you find yourself running out of things to say after 8 pages you probably have not done enough research or have defined your topic too narrowly. On the other hand, unless a paper is extraordinarily well written or insightful readers' attention can begin to wander after 25 pages or thereabouts. My way of putting this is that every page over the 25th has to earn its right to exist. Obviously in this days of multiple font sizes, margins that expand and contract at will, and the like, page numbers are perhaps not the best rubric for this. The point is that I don't count pages or words or letters, but I do "count" ideas.
There are also usually issues about format. I am perfectly happy to accept any reasonable format, but you ought to make the format as easy on the reader as possible. At a minimum the paper should be double spaced, a complete list of references should be appended at the end, and sources for important ideas should be documented in the text. The latter can be a bit tricky. Generally, you do not need to document generally accepted ideas, such as dates (unless controversial), concepts associated with major thinkers that are part of the educated public domain, and the like. For example, you need not give a particular citation to Darwin in discussing his theory of evolution. One test I like to suggest is that the reader (in this case me) should be able to find out where you got ideas that might be controversial, misleading, or wrong. So if you write something along the lines of: "Americans seem to have an ambivalent attitudes toward violence, deploring some forms and accepting others" you need not document the statement in part because it is obvious and in part because it is the kind of statement that will probably be amplified. If you then go on to say, "Surveys of public opinion consistently show that ..." I would want to know where these survey data came from, and since you have indicated "consistently" presumably you would need either to cite several sources or a summary statement. In the latter case it might be useful to say something along the lines of "for a summary see, Jones, 1999". You can document these sources in many ways. The standard social science way is (Jones, 1999) but you may also use footnotes if you wish. I prefer footnotes to endnotes if your computer program does both, but either is acceptable.