Doesn't the change from a transaction go into a separate wallet address, say you have 2 BTC in your wallet adress and you send 1 BTC to someone, doesn't the remainder...or change go into a separate address?
That depends on the wallet you are using, and whether that 2 BTC was received as a single payment or multiple payments to the same address.
Trezor (and other good HD wallets) always spend the entire amount on the address and the change goes to a new address every time as WarrEagle described in his example. So every address generated by the wallet gets used exactly twice: once when the BTC are sent to the address and once when they are spent.