This probably is a topic for b10 but I'll have a go:
Computer science is about how Computers work and are designed.
Of course this is pretty useless without the software to guide it so I can see how you have a problem with the distinction.
I guess that one topic that would be Computer science only could be the creation of biological components that lead electricity - or create electricity. That way you could potentially have self-reparing computers that need no traditional external energy source. Or computers that grows a bigger memory when it needs it.
Beware the cyborgs are coming

The Software engineering is more of using the computer to solve a problem.
So if you want your computer to calculate the components needed for an underfloor heating system and the mass needed - You would be software engineering.
Again you cannot do anything with the software without the computer - but I think the emphasis is a bit different.
I think...
