How do I get a masters degree in something? Does it have to be

Generally you have to have the associated Bachelors, unless they're very similar. CS -> Chemistry is probably too far of a stretch.

For chemistry, it's rare to get a masters in it. You apply for a PhD but if you leave early you get masters as a "consolation" prize in the US.

>>18698603
Professor writing here

While most grad school applicants naturally enough majored in the same field, crossing fields is perfectly possible. You'll just have to make the case in your application letter/essay. ("Although I majored in CS as an undergrad, largely because I had committed to it before I began to lose interest, the two chemistry classes I took opened my eyes to my real passion.......")

Chemical computing, simulations, ... pure chemistry def. not.

>>18698704
Bullshit. He doesn't have 4 years of chemistry knowledge ...

>>18699525
It's really not necessary