There are different ways to tell different scents from each other! Obviously smelling is one good way, but there are other ways! One way that I could use is gas chromatography. The results given for each scent would vary depending on their chemical make up, so this would be seen if we use gas chromatography!
So scientists are crafty when it comes to detecting things! we’ve got loads of kit we can use to analyse particles! In the old days before all the cool technology we have today, people used to record the smell(!) and taste(!?!) of chemicals they had made (i don’t recommend this – its pretty dangerous).
Louise has mentioned one bit of kit. But we have some more as well! If you shine an infrared light at particles – the different types of links holding all the atoms together – called bonds – can absorb the light (and makes them stretch). We can look at the light coming through the other side and its missing the bits that were absorbed – telling us what bonds (and therefore what chemicals) are in the particle.
We can also take an MRI scan of particles in a special machine called an NMR scanner. It uses a large magnet and radio waves to tell us where all the atoms are in the sample!
If you become a scientist – I’m sure you’ll get to play with cool equipment like these things too 🙂
Hope this answers your question – let me know if you want to know more 🙂