Contractions in writing express the author's attitude toward the subject matter and the reader. In informal writing (essays, blogs, personal letters, text messages, etc.) we make use of contractions to maintain an informal attitude. In formal writing (research papers, reports, official letters, exams, etc) we avoid contractions in order to establish a more serious tone. Consider your audience and the purpose of your writing before you decide whether you should use contractions. In speech contractions are the norm.

if u want to fail :P

Generally contractions are used in casual speech and very informal writing. For something being subitted to a company, school or higher authority (governement) for example, not using contractions is the norm, however, to my knowledge no one has ever "failed" as it was put here - simply because they wrote it's, instead of "it is". (Other things must have contributed to the actual failure < you can't be expelled for using contractions ha ha). To be on the safe side, use contractions when speaking or writing very informally. ---- Source: Englishclub.com > "Contractions are very common in spoken English. They are not so common in written English. We may use contractions in a friendly letter, for example, but they are not usually correct in more formal texts such as business letters or essays. If you have to write an essay in an exam, do not use contractions. The only exception to this would be when you quote somebody within your essay, for example spoken dialogue. -----------------------However, if in writing an essay on Italki and the corrector's intention is to make your written language sound more like "natural spoken language" < which often happens, a corrector may promote the use of contractions, not knowing what you will use the essay for. So, when you write an essay for Italki, please indicate the purpose of your essay. (For formal use / and written or spoken use). :) Nancy

For a research paper, you need to use a formal style. This means no contractions, and also spell out numbers as words (unless you have all the data in a table, or deal with large numbers often). Definitely use "It is necessary to...", in your case.

No, it is not. You will lose points if you do that!