Difference in Colour:
All the three metals have slightly different colours and it is really difficult for a layman to differentiate between them. However, one can easily point out difference if they know about the difference in them. Copper looks somewhat rusty/brownish in colour. On the other hand, Brass is brighter in colour and contains lighter finish. Bronze is much darker than the other two metals and does not shine much compared to the others. Overall, bronze is the darkest metal among the three, and Brass is lightest in colour.
Related : How To Separate Precious Metal
Difference in Durability:
Copper, in its purest form, is durable and is very hard to break. Copper is normally used in creating bent shapes and can also be stretched without any damage. Brass is also durable. However, it is not as flexible as copper is. Brass can break because of corrosion. Overall, Brass is durable, but not durable as copper and cannot be considered as flexible at all. Bronze, on the other hand, is tough to break and is durable too. Even though, bronze is not flexible in all the situations, it has the ability to resist corrosion process.
Difference in Magnetic Capability:
The other way to tell the difference is contains magnetic test. For that purpose, you should have a heavy-duty magnet. Brass is the only metal that gets attracted towards the magnet when it comes close to it. Make sure that you are using a heavy duty magnet, because brass is not heavily attracted towards the magnet. Therefore, only a heavy duty magnet will be able to attract it slightly. Bronze and Copper, on the other hand, will never get attracted towards a magnet, even if placed near the strongest magnet on this planet. As a result, one can easily point out brass if the material gets attracted towards the magnet.