ALL aspects of the written report should differ. Copying or using a laboratory report from a previous semester. This is a great way to find out firsthand what it is like to be suspended or expelled from the University. Direct copying or even using an old lab report as a template are violations. Contrary to what you may think, this is also easily detected.
Students have unique writing styles that can be easily spotted.
In addition, some instructors photocopy old lab reports at random. Copying another student's files or printouts is plagiarism. Data obtained by other researchers such as melting points, NMR shifts etc. Any sentence or passage that is used verbatim or paraphrased . Concepts, ideas or conclusions that are not intuitively obvious and are not your own.