Copper and brass are two very similar looking metals but there are many occasions when it's useful to be able to differentiate between brass and copper pipes.
Copper is a naturally occurring metal which is fairly unique in the fact that it has a gold like color. Most metals (with the exception of gold) are silver in color. Brass is a man made alloy of copper and zinc mixed together.
Step 1 - Looking at the Color
One of the easiest ways to tell the difference between copper and brass is to look at the color. At first glance the two can seem very similar however there are differences. If you have an item that you know is made out of copper then compare the color and decide whether it's brass or copper.
Copper has a red tinge to it and will go a lovely shade of green when it starts to corrode. The statue of liberty is made out of copper which has corroded.
Step 2 - Listening to the Pipes
Tap the pipes and listen to their sound. Copper is a softer metal which should produce a smoother sound. Brass is slightly harder and should produce a more defined note.
Step 3 - Looking for Markings
Some pipes will have markings on it to show that it is copper or brass. Anything with a number starting with C will be made from copper.
Step 4 - Scientific Analysis
The final option would be to send a sample of your pipe off to the lab for testing.