What is the most effective way of starting a presentation for students?
It depends on where you're presenting and who you're presenting to. If this seminar/conference/class has a moderator who introduces you, then you don't need to introduce yourself. Typically, this will be the case, instead of them just sending you on stage without an introduction.

Either way, begin your presentation with a motivating example, which might also explain why you're qualified to talk about the subject to your audience. "You might not think chemistry has a lot to do with squirrels, but it was recently discovered that squirrels' pineal glands secrete a unique chemical that..."

Since you're speaking to other students, be sure to keep the talk at a level that they can understand without a particular background in your field. And once you've started well, do the rest of the presentation well too.