I know that conductors contain "free electrons"?

So lets say hypothetically im using copper for a conductor and it hypothetically has 5 "free electrons" when i make a circuit are new electrons created or are these 5 the only ones that move around the circuit. Also does the size of the conductor determine the amount of free electrons? Meaning if I have a 5 foot piece of copper does it have more electrons then a 2 foot piece?