Your paper should be two pages, 1.5 spaced, 12 point font (Times New Roman, Arial, or any other easy-to-read font), 1 inch margins all around. It should also include a header with your name, the lab you are researching, your course section number, and the date of your writing submission. It is acceptable for the paper to be longer, but in no circumstances should the text of your paper exceed 4 pages. If you wish to include pictures, you may do so, but they do not count towards the two pages of text.
As a word of advice: Read your paper aloud before you turn it in. Reading a paper aloud will help you to hear how well the paper flows (or not). If you read it aloud and something does not sound right to you, then change it before you submit it. An even better idea is to have a friend read the paper aloud to you. You will see how well the paper reads and hear if there are any sections in need of repair.
DO NOT COPY AND PASTE FROM THE INTERNET (or anywhere for that matter). Papers will be checked for plagiarism. Make sure that you give credit to your sources, and use reliable sites. The acceptable format for a paper in Chemistry class is the ACS.