The Martian: 8 Ways It Shows Hollywood How To Do Science Right

All this said, this is a science fiction movie with at least one foot firmly planted in science fact.

Growing a crop of potatoes on Mars may be easier than was once thought. Martian soil already contains nitrogen in a biologically usable form and the additional nutrients from the crew's freeze dried excrement would have fortified it with pretty much everything they would need. 

The complex system Watney builds to extract water from rocket fuel probably would work (although perhaps not quite as effectively as in the film), however, Martian soil actually has a lot of water ice locked up in it already, so all Watney would really have had to do is thaw it out.

The gravity assist was another moment that elicited a little nerdy tingle of excitement. This is a well established principle that was used by the first Apollo crews should their engines fail. If we ignore the slightly dubious fact that the NASA Administrator doesn't know what a gravity assist is, and has to have it explained to him by a student (gonna put this one down to a bit of exposition for the audience), this is one of those moments when the real science is more exciting that the science fiction.

Another thrill of excitement could be visibly felt in the cinema when Watney heads out to scavenge Pathfinder. This, for some reason, really hammered home the reality that we are a spacefaring species, so much so that we have tech just lying around on a completely different planet. It made it feel much more real for reasons  that I can't quite put my finger on.

Oh, and that Oxyliquit bomb would have worked.