All scientific papers need an aim or series of aims. Essentially, the aims describe why you carried out this particular set of experiments. So if you don’t have one, your paper doesn’t have a purpose. The aim can be presented at the end of the introduction, or in a separate section afterward (imaginatively) titled “Aims”. How it’s presented in a paper is generally down to what journal style you’re following.
So what makes an aim? In a word, specificity. Aims should not be general, or “wishy washy”. I’ve seen a lot of aims written by students that say things like “to learn about [topic x]…” This is to be avoided for several reasons. Firstly, imagine this from the readers’ point of view: they’re reading this paper to find out about a new piece of research, they’re not interested in your learning process, they want to see results.
Secondly, the general nature of that statement means that there are myriad different ways we could satisfy the condition and make it true. You could learn about the topic by reading a textbook, or watching someone else perform an experiment, or go to a university lecture on the subject. But that’s not what you’re reporting in your paper. So, you must be as specific as you can.
The structure of an aim statement will often take on the form: “to use [method x] to test [condition y].” The addition of the method makes your aim much more specific, as different methodologies may alter the outcome and therefore what conclusions you can draw. It also reflects what you’re actually reporting in your paper. The condition you’re testing should test some aspect of your hypothesis and also be as specific as possible.
You can see in this example that one of the aims from this paper is following a very similar form to that described above. As usual, the jargon is highlighted in blue. If we remove the jargon and replace it with place-holder text, we get the form: "To expand understanding of the mechanisms of [the phenomenon we're studying] we [performed certain experiments] and then compared them to [previous data]". Howden et al., (2011)
In the above example, the general term “expand understanding” goes against what I’ve said previously about being specific. However, if you read the paper, you’ll see that the researchers were in the dark a little as to what was going on and didn’t have an obvious candidate to study. Instead they went searching for the thing responsible for the phenomenon they were interested in. Even so, they have included methodology in their aim statement, making it as specific as possible, given their project goals and the knowledge they had at the time.
This kind of “blue sky” open ended research obviously has to have more general aims because you’re never quite sure what you’re going to find - and sometimes you don’t know what you’re looking for. This contrasts with “directed research” which has specific objectives in mind. These could be things like “does [chemical compound x] kill cancer tumours?” or “do bowling balls and feathers actually fall at the same speed without air resistance?”
To summarise, think carefully about the objectives of the experiments in your report and ask yourself what they were designed to show. Condense these down to simple, testable statements and you have the aims.