As jerf said, amortized complexity is discussed in a CS2-style course (in the second semester) when implementing array lists, but invariants are also discussed in the same course when implementing binary heaps or balanced trees (typically AVL or red-black).

It's also plausible that loop or class invariants are discussed in a CS1 course to ensure that your objects don't end up in invalid states after the execution of a loop/method. But maybe the exact word "invariant" is not used as such here.